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Full text of "Byte Magazine Volume 07 Number 04 - Human Factors Engineering (RESCAN)"

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ftPFJIL. 1982 Vol. 7, No. 4 

$2.95 in USA 

$3.50tft>. Canadaftl .85 in U.K. 

A McGraw-Hill Publication 




HUMAN FACTORS ENGINEERING 

1X0 TELECOMPUTING SYSTEM 



A new small computer 
that won't limit you tomorrow 




New Cromemco System One shown with our 
high-capability terminal and printer. 




Expandability 



Here's a low-priced computer that won't run out 
of memory capacity or expandability halfway 
through your project. 

Typically, computer usage tends to grow, requir- 
ing more capability, more memory, more storage. 
Without a lot of capability and expandability, your 
computer can be obsolete from the start. 

The new System One is a real building-block 
machine. It has capability and expandability by the 
carload. 

Look at these features: 

■ Z80-A processor 

■ 64K of RAM 

■ 780K of disk storage 

■ CRT and printer interfaces 

■ Eight S-100 card slots, allowing expansion 
with 

— color graphics 

— additional memory 

— additional interfaces for telecommunica- 
tions, data acquisition, etc. 

■ Small size 

GENEROUS DISK STORAGE 

The 780K of disk storage in the System One 
Model CS-1 is much greater than what is typically 
available in small computers. But here, too, you 
have a choice since a second version, Model 
CS-1H, has a 5" Winchester drive that gives you 
5 megabytes of disk storage. 

MULTI-USER, MULTI-TASKING 
CAPABILITY 

Believe it or not, this new computer even offers 
multi-user capability when used with our advanced 
CROMix* operating system option. Not only does this 
outstanding O/S support multiple users on this com- 
puter but does so with powerful features like multi- 



ple directories, file protection and record level lock. 
cromix lets you run multiple jobs as well. 

In addition to our highly-acclaimed CROMix, there 
is our CDOS*. This is an enhanced CP/M + type system 
designed for single-user applications. CP/M and a 
wealth of CP/M-compatible software are also 
available for the new System One through third- 
party vendors. 

COLOR GRAPHICS/WORD PROCESSING 

This small computer even gives you the option of 
outstanding high-resolution color graphics with our 
Model SDI interface and two-port RAM cards. 

Then there's our tremendously wide range of 
Cromemco software including packages for word 
processing, business, and much more, all usable 
with the new System One. 

ANTI-OBSOLESCENCE/LOW-PRICED 

As you can see, the new One offers you a lot of 
performance. It's obviously designed with anti- 
obsolescence in mind. 

What's more, it's priced at only $3,995. That's 
considerably less than many machines with much 
less capability. And it's not that much more than 
many machines that have little or nothing in the 
way of expandability. 

Physically, the One is small — 7" high. And it's all- 
metal in construction. It's only 14Va" wide, ideal for 
desk top use. A rack mount-option is also available. 

CONTACT YOUR REP NOW 

Get all the details on this important building-block 
computer. Get in touch with your Cromemco rep 
now. He'll show you how the new System One can 
grow with your task. 



*CROMIX and CDOS are trademarks of Cromemco Inc. 
tCP/M is a trademark of Digital Research 



a 



Cromemco"" 

i ncorporated 

280 BERNARDO AVE., MOUNTAIN VIEW, CA 94040 • (415)964-7400 

Tomorrow's computers today 



Circle 469 on Inquiry card. 



CROMIX RLE SYSTEM 

/(root dlraclory) 




CROMIX * — Cromemco's outstanding 
UNIX— like operating system 



cromix is just the kind of major 
development you've come to expect 
from Cromemco. After all, we're 
already well-known for the most 
respected software in the microcom- 
puter field, 

And now we've come up with the in- 
dustry's first UNix-lookalike for 
microcomputers. It's a tried and proven 
operating system. It's available on both 
5" and 8" diskettes for Cromemco 
systems with 128K or more of memory. 

Here are just some of the features you 
get in this powerful Cromemco system: 

• Multi-user and multi-tasking 
capability 

• Hierarchical directories 

• Completely compatible file, 
device, and interprocess I/O 

• Extensive subsystem support 

FILE SYSTEM 

One of the important features of our 
cromix is its file system comprised of 
hierarchical directories. It's a tree struc- 
ture of three types of files: data files, 



*CROMIX is a trademark of Cromemco, Inc. 
tUNIX is a trademark of Bell Telephone Laboratories 



directories, and device files. File, 
device, and interprocess I/O are com- 
patible among these file types (input and 
output may be redirected inter- 
changeably from and to any source or 
destination). 

The tree structure allows different 
directories to be maintained for different 
users or functions with no chance of 
conflict. 

PROTECTED FILES 

Because of the hierarchical structure 
of the file system, cromix maintains 
separate ownership of every file and 
directory. All files can thus be protected 
from access by other users of the 
system. In fact, each file is protected by 
four separate access privileges in each 
of the three user categories. 

TREMENDOUS ADDRESS SPACE, 
FAST ACCESS 

The flexible file system and general- 
ized disk structure of cromix give a disk 
address space in excess of one gigabyte 
per volume — file size is limited only by 
available disk capacity. 



Speed of access to disk files has also 
been optimized. Average access speeds 
far surpass any yet implemented on 
microcomputers. 

C COMPILER AVAILABLE, TOO 

Cromemco offers a wide range of 
languages that operate under cromix. 
These include a high-level command 
process language and extensive sub- 
system support such as cobol, Fortran 

IV, RATFOR, LISP, and 32K and 16K basics. 

There is even our highly-acclaimed 
'C compiler which allows a program- 
mer fingertip access to cromix system 
calls. 

THE STANDARD O-S 
FOR THE FUTURE 

The power and breadth of its features 
make cromix the standard for the next 
generation of microcomputer operating 
systems. 

And yet it is available for a surprisingly 
low $595. 

The thing to do is to get all this 
capability working for you now. Get in 
touch with your Cromemco rep today. 



Q Cromemco ™ 
i n c o r p oral e d 
280 BERNARDO AVE., MOUNTAIN VIEW, CA 94040 • (415)964-7400 
Tomorrow's computers today 



Circle 470 on inquiry card. 



In The Queue 



BITE 



Volume 7, Number 4 



April 1982 



Features 



32 The Generic Word Processor, A Word-Processing 
System for All Your Needs by Philip Schrodt / You'll be amazed 
by this product's versatility. 

40 Use Infrared Communication for Remote Control by 

Steve Garcia / Texas Instruments' SN76B32AN Infrared Remote-Control 
Receiver simplifies the tough job of receiving modulated infrared light. 

50 How to Use Color Displays Effectively, A Look at the 
Elements of Color Vision and Their Implications for 
Programmers by John Durrett and Judi Trezona / Color is 
becoming an affordable option for personal computers, but like any new 
tool, it has special limitations and requirements. 

56 A Human-Factors Case Study Based on the IBM 
Personal Computer by Robert G. Cooper Jr., Paul Thain 
Marston, John Durrett, and Theron Stimmel / Members of a 
human-factors evaluation team put the Personal Computer to the test. 

108 A Human-Factors Style Guide for Program Design 

by Henry Simpson / Design considerations that make programs user- 
friendly. 

134 The Atari Tutorial, Part 8: Generating Sound with 
Software by Bob Fraser / The sound capabilities of the Atari 400 and 
BOO are influenced by the software technique used. 

1 58 A Pofrjtpourrl of Ideas, Fifth In a Series by William 
Barden Jr. / Three inexpensive hardware and software projects for a tone 
generator, a telephone dialer, and an RS-232C output channel. 

186 The Input/Output Primer, Part 3: The Parallel and 
HPIB (IEEE-488J Interfaces by Steve Leibson / An introduction to 
two common interfaces between computers and other devices. 

212 User's Column: The Osborne 1, Zeke's New Friends, 
and Spelling Revisited by Jerry Pournelle / A seasoned computer 
user takes a look at new products and updates. 

242 Designing the Star User Interface by Dr. David 
Canfield Smith, Charles Irby, Ralph Kimball, Bill Verplank, and 
Eric Harslem / The Star User Interface adheres rigorously to a small set of 
principles designed to make the system seem friendly by simplifying the 
human-machine interface. 

284 Designing a Text Editor? The User Comes First by 

Steven Jong / A system's power is measured in ease of use. 

302 Managing Words: What Capabilities Should You 
Have with a Text Editor? by Craig A. Finseth / The ideal text 
editor is defined drawing on the experience of many users. 

322 A Disk Operating System for FORTH, An In-depth 
Look at How a DOS Operates by Peter Reece / Develop a DOS 
for the FORTH language and gain an understanding on how all DOSes 
operate. 

380 MOD III: TRS-80 Model III Features for Your Model I 

by Joe W. Rocke / Add video line print, selectable cursor, and automatic 
key repeat to your TRS-BO Model I. 



398 Binary-Coded Text, A Text-Compression Method by 

Dr. Richard Tropper / You can trim text size by 40 percent by encoding 
common character strings. 

439 Career Opportunities In Computing by Jacqueline 

Johnston / Hobby-level interest in computers can lead to a career in the 
computer industry. 

447 Converting Apple DOS and Pascal Text Files by John 
B. Matthews / Now you can exchange information between DOS 3.3 
and Pascal Operating Systems. 

464 A Simple Multiprocessor Implementation by John 

Harrington / A simple connection can be the start of a multiprocessing, 
multitasking system. 

472 An Introduction to NSC Tiny BASIC, The Language of 
the INS8073 by Jim Handy / National Semiconductor's unique version 
of Tiny BASIC combines the elegance and efficiency of assembly language 
with the convenience of a high-level language. 



Reviews 



76 The Hewlett-Packard Interface Loop-HPILby Robert Katz 

96 Strawberry Tree's Dual Thermometer Card for the Apple by Dr. 

William Murray 

312 Two Word Processors for North Star by Edgar F. Coudal 

371 Selector IV by Micro-Ap, An Information-Management Program by 

Jack L. Abbott 



Nucleus 



6 Editorial. A Revolution in Your Pocket 
20 Letters 
102, 1 55, 240 Book Reviews: Software Psychology: Human Factors 
in Computer and Information Systems; The Mind's I; Handbook of 
Digital IC Applications 
104 Product Description: The Epson HX-20. The First Byte-sized 

Computer 
362 Technical Forum: MicroShakespeare^ 
414 BYTELINES 

418 BYTE's Bits 

419 What's New? 
429 Ask BYTE 

432, 436 Programming Quickies: A BASIC Program for Home 

Cryptography; Base Conversion on the TRS-80 Pocket Computer 
435 Software Received 
482 System Notes: Easy-Entry Program for Radio Shack's Color Computer 

489 Clubs and Newsletters 

490 Books Received 

491 Event Queue 
542 Unclassified Ads 
542 BOMB. BOMB Results 
544 Reader Service 




Page 40 



Page 50 



Page 56 



Page 76 



April 1982 © BYTE Publications Inc 3 



m 

Editor in Chief 
Christopher Morgan 

Managing Editor 

Mark Haas 

Technical Editors 

Gregg Williams, Senior Editor; 

Richard S. Shuford; Curtis P. Feigel; 

George Stewart; Arthur LittJe; 

Stanley Wszola; Steve Garcia; Mark Dahmke 

Philip Lemmons; Allan Lundell. Consulting 

Editors; Jon Swanson. Drafting Editor 

Copy Editors 

Beverly Cronin, Chief; Faith Hanson; 
Warren Williamson; Anthony J. Lockwood; 
Ann Graves; Linda M. Evers; Hilary Selby Polk; 
Elizabeth Kepner 

Assistants 

Faith Ferry; Debe Wheeler; 
Beverly Jackson 



Production 

David R. Anderson. Assoc. Director; 
Jonathan M. Graves. Creative Consultant; 
Patrice Scribner; Damian Henriques;. Jan 
Muller; Linda J. Sweeney; Virginia Reardon; 
Sherry McCarthy, Chief Typographer; 
Debi Fredericks; Donna Sweeney; 
Valerie Horn 

Advertising 

Thomas Harvey, Director; Marion Carlson; 
Rob Hannings; Deborah Porter; 
Vicki Reynolds; Cathy A. R. Drew; 
Jacqueline Earnshaw. Reader Service 
Coordinator; Wai Chiu Li, Advertising/ 
Production Coordinator 



Circulation 

Gregory Spitzfaden, Manager; 
Andrew Jackson, Asst. Manager; 
Agnes E. Perry; Barbara Varnum; 
Louise Menegus; Pinky Krulis; 
Sheila A. Bamford 
James Bingham, Dealer Sales; 
Deborah J. Cadwell, Asst. 
Linda Ryan 



Controller's Office 

Daniel Rodrigues, Controller; 
Mary E. Fluhr, Acct. & DIP Mgr.; Karen 
Burgess; Jeanne Cilley; Linda Fluhr; 
Vicki Bennett 

Traffic 

N. Scott Gagnon; Scott Jackson, 
Kathleen Reckhart 

Publishers 

Virginia Londoner; Gordon R. Williamson; 

John E. Hayes, Associate Publisher; 

Cheryl A. Hurd; Michele P. Verville, Publisher's 

Assistants; 



Officers of McGraw-Hill Publications Com- 
pany: Paul F. McPherson, President; Executive 
Vice Presidents: Daniel A. McMillan, III, Gene 
W. Simpson; Senior Vice President-Editorial: 
Ralph R. Schulz; Vice Presidents: Kemp Ander- 
son, Business Systems Development; Harry L. 
Brown, Special Markets; Robert B. Doll, Circula- 
tion; James E. Hackett. Controller; Eric B. Herr, 
Planning and Development; H. John Sweger, 
Jr., Marketing. 

Officers of the Corporation: Harold W. 
McGraw Jr., Chairman and Chief Executive 
Officer; Joseph L. Dionne, President and Chief 
Operating Officer; Robert N. Landes, Senior Vice 
President and Secretary; Ralph J. Webb, 
Treasurer. 




In This Issue 

As computer technology continues to make inroads into our lives, the 
man/machine interface assumes greater importance in the total system design. 
Human-factors engineering, our theme this month, is the discipline concerned 
with the need for friendly computers. Our cover, photographed by Paul Avis, 
features a new, user-friendly product, the IXO Telecomputing System. For a 
detailed description of this hand-held terminal see Chris Morgan's editorial. 

To help you make your systems user-friendly, we present "A Human- 
Factors Style Guide for. Program Design" by Henry Simpson and "De- 
signing the Star User Interface" by Dr. David Canfield Smith, Charles Irby, 
Ralph Kimball, Bill Verplank and Eric Harslem. In "A Human-Factors Case 
Study Based on the IBM Personal Computer," Robert G. Cooper Jr., Paul Thain 
Marston, John Durrett, and Theron Stimmel discuss the Personal Computer 
from a human-factors perspective. Steve Garcia demonstrates how to use in- 
frared systems, William Barden Jr. presents a collection of projects for the 
TRS-80 Color Computer, Gregg Williams treats us to a sneak preview of 
Epson's new portable computer, and Bob Katz reviews the Hewlett-Packard 
Interface Loop. 



BYTE is published monthly by BYTE Publications Inc, 70 Main St, Peterborough NH 0345B, phone (603) 
924-92B1 , a wholly-owned subsidiary of McGraw-Hill, Inc. Address subscriptions, change of address, USPS Form 
3579, and fulfillment questions to BYTE Subscriptions, POB 590, Martinsville NJ 08836. Second class postage paid 
at Waseca, Minnesota 56093 - USPS Publication No. 528890 (ISSN 0360-5280). Canadian second class registra- 
tion number 932 1 . Subscriptions are S 1 9 for one year, S34 for two years, and S49 for three years in the USA and 
its possessions. In Canada and Mexico, S21 for one year, S38 for two years, S55 for three years. S43 for one year 
air delivery to Europe. S35 surface delivery elsewhere. Air delivery to selected areas at additional rates upon re- 
quest. Single copy price is S2.95 in the USA and its possessions, S3.50 in Canada and Mexico, S4.50 in Europe, 
and S5.00 elsewhere. Foreign subscriptions and sales should be remitted in United States funds drawn on a US 
bank. Printed in United States of America. 

Address all editorial correspondence to the editor at BYTE, POB 372, Hancock NH 03449. Unacceptable 
manuscripts will be returned if accompanied by sufficient first class postage. Not responsible for lost manuscripts or 
photos. Opinions expressed by the authors are not necessarily those of BYTE. Entire contents copyright © 1982 
by BYTE Publications Inc. All rights reserved. Where necessary, permission is granted by the copyright owner for 
libraries and others registered with the Copyright Clearance Center (CCC) to photocopy any article herein for the 
base fee of S 1.00 per copy of the article or item plus 25 cents per page. Payment should be sent directly to the 
CCC, 21 Congress St, Salem MA 01970. Copying done for other than personal or internal reference use without 
the permission of McGraw-Hill is prohibited. Requests for special permission or bulk orders should be addressed to 
the publisher. 

BYTE® is available in microform from University Microfilms International, 300 N Zeeb Rd, Dept PR, Ann 
Arbor Ml 48106 USA or 18 Bedford Row, Dept PR, London WCIR 4EJ England. 



Office hours: Mon-Thur 8:30 AM - 4:30 PM, Friday 8:30 AM - Noon, Eastern Time 



4 April 1982 © BYTE Publications Inc 





" . . . stands well above 
other S-100 graphics dis- 
plays in its price and per- 
formance range." 

BYTE, Product Review 




. .better monochromatic 
. display . . 



ELECTRONIC DESIGN, 
1981 Technology Forecast 



MICROANGELO 

HIGH RESOLUTION GRAPHICS SINGLE BOARD COMPUTER 

5 1 2 x 480 resolution black and white and vivid color displays 




RS- 170 com- 
posite or direct 
drive output 

Local or external 
sync generation 

4MhzZ80 
microprocessor 

60 hertz real- 
time clock 

8 level interrupt 
tie-in 

IEEE SI 00 bus 
compatible 



Screenware™ Pak I 

A 4K byte operating system resident in PROM on 
MicroAngelo™. Pak I emulates an 85 character 
by 40 line graphics terminal and provides over 
40 graphics commands. Provisions exist for user 
defined character sets and directly callable user 
extensions to Screenware™ Pak I. 

Screenware™ Pak II 

An optional software superset of Pak I which 
adds circle generation, polygon flood, program- 
mable split screen for separate graphics and ter- 
minal I/O, relative coordinates, faster vector and 
character plotting, a macro facility, full UCSD 
Pascal compatibility, and more. 



Light pen 
interface 

Time multi- 
plexed refresh 

4K resident 

Screenware™ 

Pak I operating 

system 

32KRAM 

isolated from 

host address 

space 

High speed 

communications 

over parallel 

bus ports 



And now.. .COLOR!! 

The new MicroAngelo™ Palette board treats from 
2 to 8 MicroAngelos as "bit planes" at a full 
512 x 480 resolution. Up to 256 colors may be 
chosen from 16.8 million through the program- 
mable color lookup table. Overlays, bit plane 
precedence, fade-in, fade-out, gray levels, blink- 
ing bit plane, and a highly visual color editor are 
standard. 

Ask about our multibus and RS-232 versions. 



Circle 363 on inquiry card. 



12310 Pinecrest Road • Reston, VA 22091 • (703)476-6100 • TWX: 710-833-0684 



Circle 146 on inquiry card. 



foot-note, n. 1. a note or 
comment at the end of a 
page, referring to a specific 
part of the text on the page. 
2. an essential program for 
the serious WordStar user. 



FOOTNOTE™ brings full foot- 
noting capabilities to WordStar™. 

FOOTNOTEautomatically num- 
bers both footnote calls and foot- 
notes, and formats the text, 
placing footnotes on the bottom 
of the correct page. At the user's 
option, the footnotes can also be 
removed from the text file to a 
separate note file. 

Footnotes can be entered singly 
or in groups, in the middle or at 
the end of paragraphs, or in a 
completely separate note fi le. After 
running FOOTNOTE the user can 
re-edit the text, add or delete 
notes, and run FOOTNOTE again 
to re-number and re-format the 
WordStar file. 

The price is $125., and includes 
PAIR.acompanion programthat 
checks that printer commands 
to underline or set in BOLDFACE, 
are properly terminated. FOOT- 
NOTE and PAIR require CP/M™, 
WordStar, 48K RAM and a Z80 or 
8080/85 computer. 



SOFTIWE 
SOFTWARE 
DIGIL4L/M4RKETING 

DIGIT/L/VMRKETING" 

2670 Cherry Lane • Walnut Creek • CA 94596 



(415) 938-2880 

Telex #17-1852 (DIGMKTG WNCK) 



PRO/TEM 



FOOTNOTE and PAIR trademarks of PRO/TEM Software Inc 
WordStar trademark of MicroPro Int'l 
CP/M trademark of Digital Research 



Editorial 



A Revolution 
in Your Pocket 



by Chris Morgan, Editor in Chief 



Imagine a terminal that costs about $500 and can: 

• access the Source, CompuServe, Dow Jones, or other remote database or 
computer services 

• automatically handle the protocols to access these services so that you 
need only enter your password to be online 

• have a full ASCII character set 

• have a built-in modem with autodialer and full- and half -duplex 
capability 

• be able to emulate other terminals 

• have an uninterruptible power supply 

• fit in your pocket 

• operate from a battery 

Sounds amazing, doesn't it? Yet it's not fantasy; the product does exist. It's 
called the IXO Telecomputing System (hereafter referred to as the Telecom- 
puter), and it's featured on our cover this month. 




Photo 1: The IXO Telecomputing System. It's a complete pocket terminal with built-in 
modem and autodialer that will sell for about $500. The phone number displayed is 
IXO's Access Center. 



6 April 1982 © BYTE Publications Inc 



You Get More Out of 
Percom Disk Systems. 



Expect In 



At Percom, our business is making 
disk storage systems for microcomputers 
— something we've been doing right, 
since 1977. 

From the design of rock-solid drive 
controller circuitry to quality controls that 
include 100% life testing of every drive ship- 
ped, you can expect to get more out of 
Percom Disk Systems. 

And Percom provides you with com- 
prehensive after-sales service from our 
wholly owned, fully independent customer 
service center. 

WINCHESTER 
10-MEGABYTE 
DISK STORAGE 
SYSTEMS 
Enormous 



storage capacity 
plus high speed. 
Percom 5 1 /* inch hard 
disk systems are 40 
times faster than 
single-density floppy 
mini-disks, 20 times 
faster than double- 
density units. 
Systems include a smart, four-drive controller 
featuring state-of-the-art data encoding and 
separation, adaptable industry-standard disk 
interfacing. Plug-in-compatible version for 




TRS-80* Model III computer, available 
now. Watch for IBM PC, Apple II, Atari, 
and H/Z-89 versions. Prices start at 
under $3000, including software. Also 
available with 5 or 15-Mbyte drives. 

Coming soon! Ten 
megabyte removable- 
disk cartridge drive. 

FLOPPY MINI-DISK 
STORAGE SYSTEMS 

40 or 80-track drives, single 
or dual-head, flippy or non- 
flippy— all double-density 
rated. Available in 1, 2 and 3- 
drive add-on units, 1 and 2-drive 
internal units, with full docu- 
mentation and software support. 
Add-on drives from $399, complete 
systems from $459.95. 

To learn more about quality 
Percom disk storage systems, mail 
the coupon today. Or, call toll-free 
1-800-527-1222. Ask for booklet "D". 







YES ... I'd like to know more about Percom disk 
systems. Please rush me booklet "D" 

Send to: PERCOM DATA COMPANY, INC. Dept BD1 
11220 Pagemill Road, Dallas TX 75243 



street 



city 



state 



zip 



the Drive people 

11220 Pagemill Road • Dallas TX • 75243 • (214) 340-7081 



phone number 

I'm interested in floppy disk storage for my... 
TRS-80 □ Mdl III □Mdl I niBM PC 

□ H/Z-89 DH-8 DAIM/KIM/SYM DSystem-50 

I'm interested in hard disk storage for my... 

□ IBM PC □TRS-80 Mdl III □ Apple II QAtari □ H/Z-89 

Other computer? 

(□floppy disk or □ hard disk?) 



PRICES AND SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE. 

•TRS-80 is a trademark of Tandv Radio Shack Corporation which has no 
relationship'^ Percom Data Company, inc. 
© 1981 Percom Data Company, Inc. 



PROFESSIONAL PASCAL 



Pascal/ 





il.0 



SYMBOLIC DEBUGGER 

This fourth generation version of our reliable, Z-80 
native code compiler adds the two features 
professionals ask for: 

♦ SWAT™— an interactive symbolic Pascal debugger 
that allows easy error detection. 

♦ Overlays— that allow larger programs to run in 
limited memory. 

A compiler for Professional programmers 

Pascal/Z is a true Pascal. It closely follows the Jensen 
and Wirth standard with a minimum of extensions 
designed to aid the serious program developer in 
producing extremely compact, bug-free code that 
runs FAST. 

Pascal/Z generates Z-80 native code that is ROMable 
and Re-entrant. Permits separate compilation, direct 
file access, external routines and includes a relocating 
macro assembler and Microsoft compatible linker. 
And code written for Pascal/Z is fully compatible 
with I-PAS 8000, our new native code Pascal compiler 
for Z-8000, to guarantee graceful migration to 
16 bit operation. 

Get "The FACTS about Pascal" 

Confused about which Pascal to buy? 
Pseudo-code . . . Native code . . . M, MT or 
Z? Compare the unbiased benchmarks 
x in our new booklet. Don't buy a Pascal 
compiler until you've read it. 

Call us for a free copy: 

800-847-2088 

(outside NYSJ 

or 607-257-0190 

And ask your local 
full-service 
computer dealer 
about our 
Pascal/Z 
■, demo package. 



v^lthaca Intersystems Inc. 

Micros for bigger ideas. 

Ithaca Intersystems Inc. 

1650 Hanshaw Rd • Ithaca, NY 14850 • TWX 510 255-4346 

U.K. Distributor: 
Ithaca Intersystems (U.K.)Ltd. 

Coleridge Road London N8 8ED Phone: 01-341 2447 Telex: 299568 




Editorial. 



I first saw the Telecomputer nearly a year and a half 
ago when I visited its inventors, husband-and-wife team 
Bob and Holly Doyle, at their Cambridge-based com- 
pany, Macrocosmos. The Doyles conceived of a portable 
but powerful computer terminal, and with the aid of elec- 
tronic-design wizards Michael Suchof f and Andy Barber, 
they built a limited number of prototypes. The Doyles 
later joined forces with former Mattel Electronics presi- 
dent Jeff Rochlis to form IXO Inc., the company that 
markets the Telecomputer. I received one of the proto- 
types for testing last year and I've been using it ever since. 
I'm still amazed at the features packed into its exceedingly 
small package. 

This month's theme is human-factors engineering, and 
the IXO Telecomputer is an excellent example of a ter- 
minal designed with the user in mind. The Telecomputer, 
which will be generally available this summer, has a lot 
to offer in addition to its human factoring. It has, for in- 
stance, a sophisticated security-protection system and in- 
novative, compact circuitry. I'll touch on these topics, 
but my main objective here is to discuss the implications 
of IXO's design philosophy. 




Photo 2: The Telecomputer is powered by a built-in Polaroid 
Polapulse flat battery. 




Photo 3: The FCC-registered Telecomputer is designed to at- 
tach directly to a phone using a standard modular jack. When in 
use, the terminal draws all of its power from the phone line. 



Circle 219 on Inquiry card. 



Circle 220 on inquiry card. 



A computet 1 system 
so advanced,the technology 
you 11 need later is already here. 
And waiting for your call. 

8DQ-847-2Q88 

In New York State (607) 257-0190 



ODDta% v Stkl30DD^ 

Ithaca Intersystems Inc. 
1650 Hanshaw Rd. 
RO. Box 91 

Ithaca, New York 14850 
TWX 510 255 4346 



Circle 160 on inquiry card. 




Authorized Commodore service center 
Repair of the complete fine of Commodore products 

In a hurry? Check our modular exchange program 



H '■S Com ' 3Uter 





Disc Drive 


commodore 


Printer 


HARDWARE: 




SOFTWARE: 




CBM 8032 Computer, 




ozz 


$299 


80 Column 


$1095 


Wordcraft 80 


299 


CBM 8050 Disk Drive 


1340 


Tax Preparation System 


380 


CBM 4032 Computer, 




IRMA 


380 


40 Column 


995 


Dow Jones Portfolio 




CBM 4040 Disk Drive 


995 


Management System 


115 


CBM 4022 Printer 


649 


Personal Tax 


55 


CBM VIC 20 Computer 


263 


Pascal 


229 


CBM VS 1 00 Cassette 


68 


Assembler Development 




PET to IEEE Cable 


33 


Package 


77 


IEEE to IEEE Cable 


39 


\X/ordpro4+ 


329 


BASF Diskette, Box o f 1 30 







Order TOLL FREE 
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10 AM to 4 PM CDT Monday through Friday 

Texas residents call 1+214-661-1370 
VISA, MASTER CHARGE, MONEY ORDERS, AND CO.D. 
"Certified Check" accepted; 

Units in stock shipped within 24 hours, ROB. Dallas, Texas. 
All equipment shipped with manufacturer's warranty. 

Residents of Texas, Louisiana, Oklahoma City and Tulsa, 
Oklahoma must add applicable taxes. 



Eclectic shortly will be announcing products that are designed to work 
with CBM systems. 

1. ROMIO: two RS232 ports- three parallel ports-26K EPROM 

memory-managed alternate character set, software 
contrp led- EDOS (extended DOSJ. 

2. Terminal program (options with ROMIO) 

3. EPROM programmer 

4. Front-end processor 

5. Additional firmware to be announced 

Be sure to write the address below for more information; 
dealer inquiries welcome. 



P.O. Box 1 166 • 16260 Midway Road 
Addison, Texas 75001 • (214) 661-1370 



Editorial , 




Photo 4: Four peripherals for the Telecomputer (clockwise 
from upper left): an acoustic interface (not the same as an 
acoustic coupler because the modem circuitry is already con- 
tained inside the terminal); the RS-232C interface, a video inter- 
face; and a 20-column printer. 

The Telecomputer marks the beginning of a whole new 
"genus" of computer products: no-compromise portable 
computers that are truly user-friendly. Let's take a closer 
look at its features. 

The Telecomputer comes in a small plastic case con- 
taining densely packed CMOS circuitry and a Polaroid 
Polapulse flat battery to drive it (see photo 2). The heart 
of the design is an NEC 4-bit microprocessor with IK 
bytes of CMOS RAM (random access read/write mem- 
ory). 

The keyboard, which is slightly too small for extended 
typing sessions, contains several unusual keys to help the 
naive user (and sometimes the not-so-naive user). These 
include the YES, NO, DONT KNOW, HELP, and 
PHONE keys. They are brightly colored to attract your 
attention. The HOLD, SLOW, FAST, REPT, GO BACK, 
CLR CHAR, and CLR ENTR keys are dark blue. The 
usual BREAK, ESCAPE, and CONTROL keys are gray. 
The blue and gray colors tend to keep the more complex 
keys in the background in order not to distract or in- 
timidate the beginner. 



A Session with the Telecomputer 

After you remove the Telecomputer from its box and 
turn it on, you then connect it to your telephone line by 
plugging your telephone cord's modular jack into the 
female socket at the back of the terminal (see photo 3). At 
this point the Telecomputer begins to draw all of its 
. power from the phone line while the phone is "off hook," 
i.e., while the phone is in use (a clever arrangement by 
the machine's designers). Since the phone companies re- 
quire all phone devices to draw 20 milliamps to prove 
that the devices are using the lines anyway, this becomes 
a perfect source of power for CMOS circuitry! In fact, 
telephone devices are allowed to draw 5 microamps while 
"on hook," so it becomes theoretically possible to trickle- 
charge a battery. 



10 April 1982 © BYTE Publications Inc 



Circle 380 on inquiry card. 




^^3K-fc» Hi 




/ 



*■* 



§m .;--, 






Every Apple Is Created Equal. 
But It Doesn't Have To Stay That Way. 



An Apple™ is really something. 

But from now on, it's going to be 
something much more. How come? 
Simple. We're introducing three 
revolutionary new data communica- 
tion packages, called Transend™, 
designed especially to make your 
Apple II™ rise above all others. 

Our Transend data communica- 
tions software provides access to in- 
formation utilities; complete file 
transmission of charts, VisiCalc™ 
reports, and entire programs; as well 
as all electronic mail functions. 

Transend comes in three different 
versions. You can begin economically 
with the simplest form, Transend 1, 
an intelligent terminal/file transfer 
system. As your needs increase, you 
can move up to two other Transend 
packages, without worrying about 
retraining or repurchasing. Transend 
2 gives any Apple II intelligent ter- 
minal capabilities, plus file transfer 
with complete error detection and 



automatic retransmission for de- 
manding business applications. 
Transend 3 incorporates electronic 
mail— with password security, text 
editing, mailbox with mailstop, unat- 
tended scheduling and receiving, 
automatic redialing, and much more. 



i 



The Transformation People 



Transend's support of most popu- 
lar Apple II "add-in" cards and 
modems lets you upgrade your 
Apple without hassle or unnecessary 
expense. And you'll immediately cut 
operating costs by as much as 30% 
with simple, easy-to-use menus, data 
compression and 1200-baud modem 
support. 

Nobody on the personal computer 
scene today is offering the speed, flex- 
ibility, and reliability of Transend in 
a single upgradable software system. 

Don't miss this chance to uplift 
your Apple II. Contact us or your 
dealer for all the delicious details. 

SSM Microcomputer Products, Inc., 
2190 Paragon Drive, San Jose, CA 
95131, (408) 946-7400, Telex: 171171, 
TWX: 910-338-2077. 

Apple and Apple 1 1 are trademarks of Apple 
Computer, Inc. VisiCalc is a trademark of Per- 
sonal Software, Inc. And Transend is a trade- 
mark of SSM Microcomputer Products, Inc. 



The disk drive 



I 



I 




Introducing the first totally compatible 
Floppy Disk Drive. 

Rana Systems has designed a totally 
compatible disk drive for Apple, that's better 
than Apple's. A high density, high capacity disk 
drive and controller that offers a myriad of 
features Apple never thought of. Unique advan- 
tages that get the maximum efficiency out of 
your existing Apple II* hardware and software. 

At Rana, we knew you wanted more 
storage, so we went right to the core of the 
problem. Even our most economical model is 
designed to give you 15% more storage capac- 
ity than Apple's. Our top-of-the-line unit gives 



you 4 times the capacity of Apple's comparable 
unit. Even our design is far more dramatic than 
theirs. With lines that actually complement the 
sleek Apple II computer. 

We're a step ahead of Apple because 
we have a faster step. 

Holding more information is even 
more valuable when you can get it faster. The 
Rana System track positioning mechanism is 
engineered to access three to four times faster 
track to track, with greater accuracy than 
Apple's. Our disk drive offers safeguards like 
a stall provision to protect spin motor burnout, 



Apple II is a registered trademark of Apple Computer inc. 




an advanced write protect feature that keeps 
your information where you put it, and an 
energy saving device that "powers down" when 
your disk drive is taking a break. 

We even took a bite out of Apple's price. 

Our most popular model is 25% more 
economical per byte than Apple's, providing 
you with maximum performance, superior cost 
efficiency, and totally compatible styling. It 
also comes with a free diskette containing all 
the optional software and supports you'll need 
to enhance the capacity and performance. 
And it's all backed up with an efficient service 



support system, and a full 90 day warranty. 

The Rana System Floppy Disk Drive. Just 
plug it into your Apple and all those delicious 
extra bytes will be yours. 

RanaSystems. 




Circle 353 on inquiry card. 



20620 South Leapwood Avenue, Carson. CA 90746 213-538-2353. 
For dealer information call toll free: 1-800-421-2207 
In California only call: 1-800-262-1221. Source Number TCT-654. 
See our booth at the West Coast Computer Faire Show. 



CALICO 



CP/M® 



APRIL '82 



Specify formal 

Most disk formats available. 



LANGUAGES 

Basic Microsoft 

Basic Compiler Microsoft 



disk 

wlfo /manual 

manual/ wily 



C-Basic 
CB80 
COBOL 80 
C Compiler 
Forth 
Fortran 
Fortran 80 
muLISP 
Pascal/M 
Pascal Z 
P/L 1-80 
RATFOR 
Fortran 
S-Basic 



Dig. Research 
Dig. Research 
Microsoft 
Supersoft 
Supersoft 
Supersoft 
Microsoft 
Microsoft 
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Ith. Intersys. 
Dig. Research 
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RATFOR 

Micro AP 



Tiny Pascal Supersoft 

ASSEMBLERS/UTILITIES 



$289/- 

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$269/25 

$79/25 



ACT I 
Despool 
Diagnostic I 
Macro 80 
MAC 
QS0RT 
SID 
ZSID 



Sorcim 
Dig. Research 
Supersoft 
Microsoft 
Dig. Research 
Struc. Sys. 
Dig. Research 
Dig. Research 



$152/25 

$50/- 

S84/20 

$162/ — 

$85/15 

$90/- 

$70/15 

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WORD/TEXT PROCESSING 



Edit 80 
Letteright 
Magic Wand 
Mail Merge 
NAD 

Spellguard 
Spelf Star 

Textwriter III 
WordStar 

TRS-80®/Mod. 

Z-89 

Z-90 



Microsoft 
Struc. Sys. 
Peachtree 
MicroPro 
Struc. Sys. 
ISA 

MicroPro 
Dig. Research 



$90/- 
$156/ — 
$289/45 

$108/25 
$90/- 
$225/25 
$175/40 
$100/10 



Organic Softwr $110/ — 
MicroPro $289/60 

CP/M® 

II (P & T) 



$169/- 
$140/- 
$140/- 



Series20-2 
Data Star 
FMS-80-1 
FMS-80-2 



DATA BASE MANAGEMENT 

dBASE II Ashton-Tate $594/50 

Series 20-1 Condor $249/50 

Condor $509/50 

MicroPro $245/60 

Systems Plus Call 

Systems Plus Call 

INCOME TAX 
MICRO TAX 

Lev. 1 (Indvl.) $225/- 

Lev.2(Prof.) Call 

Lev. 3 (Partner) Call 

Lev. 2 & 3 Call 

State Tax Call 

ACCOUNTING 
TCS 

G/LorA/P 

or A/R or Payroll $75/25 

All four $250/99 

ACCOUNTING PLUS™ 

G/L $439/67 

A/P $375/67 

A/R $375/67 

Payroll $375/67 

Inventory $375/67 

Sales Order S375/67 

Point of Sale $375/67 

Purch. Order $375/67 

PEACHTREE-SERIES 5 

G/L 

A/P 

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Payroll 

Inventory 

Sales Invoice , 

ANALYSIS/MODELING 

CalcStar MicroPro $229/45 
Milestone Organic Softwr $269/— 

muMATH/muSIMPMicrosoft $225/— 

Supercalc Sorcim $259/ — 

Worksheet Soho Group $185/ — 



WORD STAR 
REDUCED 



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software . . . with lots of technical support 
CALICO (213)475-8104 

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I.U.S. 

Datadex 

Easy Writer (40 col) 

Easy Mailer (40 col) 

Pro. Easy Mailer 
Pro. Easy Writer 

MICROPRO 

Mail Merge $97 

Super Sort I $159 

Word Star $260 

WordStars Mail Merge $349 

MICROSOFT 

A.L.D.S. $105 

Basic Compiler S320 

Fortran-80 $175 

16K RAM Card $149 

Z-80 Soft Card $295 



APPLE II® 


PEACHTREE 












$219 


$258 

$88 

$61 

$123 

$149 

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A/R 




$219 


A/P 




$219 


Payroll 
Inventory 
Mail. List 




$219 
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HOWARD SOFTWARE 

Income Tax 

VISIC0RP 

Desktop Plan II 

VisiCalc 

VisiDex 

VisiFile 

VisiPlot 

VisiTerm 

VisiTrend/VisiPlot 



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MASTER CHARGE/VISA 



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(213)475-8104 

Add $3.50/item for shipping, handling. Overseas add $1 0. California residents 
add 6% sales tax. Allow time for checks to clear. Prices subject to change 
without notice. All items subject to availability. ©Registered trademark. 



Editorial 



14 April 1982 © BYTE Publications Inc 



Circle 71 on inquiry card. 



After you hit the ON switch, the unit's liquid-crystal 
one-line display begins presenting a series of questions in 
menu format. The first query you see is "ACCESS 
CENTER?" The best way to learn about the unit is to dial 
the Access Center, a remote computer resource center 
maintained by IXO to service Telecomputer customers. 
You simply type in the telephone number and the unit 
automatically dials it. The Telecomputer senses whether 
your phone line is Touch-Tone or rotary-dial and sends 
out the appropriate signals. Once online, you can experi- 
ment with the simulated services offered by the Access 
Center, including a checkbook-balancing program, a 
travel-agency simulation that demonstrates booking 
airline flights, a television guide database to help you find 
TV show times, and so on. The main purpose of this exer- 
cise is to illustrate the advantages of services using plain 
English dialogue back and forth between the user and the 
computer. In time, real versions of such computer ser- 
vices will be available. When connected to the Access 
Center, you can always press the HELP key if you get 
stuck and get a more detailed explanation of what to do 
next. You can also press the DON'T KNOW key if in 
doubt as to the correct reply to the computer's questions. 
(If only the existing databases had these features!) The 
Telecomputer's designers have been trying for some time 
to convince the people who run the databases to adopt 
these user-friendly approaches. Let's hope they do. 

The most important feature of the Access Center is that 
it can download protocols for The Source, CompuServe, 
and Dow Jones into your terminal's RAM. (These were 
the three services available at the time I evaluated the 
unit; more will undoubtedly be added later.) Download- 
ing protocols takes about 30 seconds and needs to be 
done only once because the information is permanently 
stored in the terminal as long as the battery holds up, 
which is at least a year — longer if you're "off-hook" fre- 
quently. Once you're connected, the Access Center asks 
you to type in a password that you must use in all future 
dealings with the Center and also asks for your name. 

I was surprised the second time I called the center to 
find that it greeted me with "HELLO CHRIS. PASS- 
WORD?" It's hard to convey the excitement of seeing a 
message like this on a miniature terminal connected 
directly to your phone line. Future shock, indeed. 

The next time I used the terminal, I decided to get on 
the Dow Jones database and analyze some stocks. I 
powered up the Telecomputer, entered my password, 
and it immediately asked "DOW JONES?" The down- 
loading had worked! Out of curiosity I pressed NO and 
the terminal stepped to the next item: "THE SOURCE?" 
NO again. "COMPUSERVE?" NO. "MANUAL AC- 
CESS?" (The latter mode lets you dial any general data- 
base or computer by entering a telephone number.) I 
cycled around to "DOW JONES?" again and pressed 
YES. (Incidentally, you can type "yes", "Y", hit the YES 
key, or the ENTER key to tell the terminal yes. The 
designers have obviously thought of every possibility to 

Circle 333 on inquiry card. » 




10 USE YOUR EPSON 

WITHOUT WASTING 
COMPUTER 





Your computer is capable of sending data 
at thousands of characters per second but 
the Epson can only print 80 characters per 
second. 

This means your computer is forced to 
wajt for the printer to finish one line before it 
can send the next. A waste of valuable time. 

THE NEW MICROBUFFER™ 
ACCEPTS DATA AS FAST AS 
YOUR COMPUTER CAN SEND IT. 

Microbuffer stores the data in its own 
memory buffer and then takes control of 
the printer. This frees your computer for 
more productive functions. 

PARALLEL OR SERIAL 

Microbuffer model MBP-16K is a 
Centronics-compatible parallel interface 
with 16,384 bytes of on-board RAM for 
data buffering. 

The MBS-8K is a full-featured RS-232C 
serial interface with both hardware and 
software (X-On/X-Off) handshaking, baud 
rates from 300 to 19,000 and an 8,192 byte 
RAM buffer. 

SIMPLY PLUG IT IN. 

Either model fits the existing auxiliary 
interface connector inside the Epson MX-80, 
MX-80 FfT or MX-100 without modification, 
and is compatible with standard Epson 
cables and printer control software, 
including GRAFTRAX-80. 

JUST $159.00* 

When you think how much time Microbuffer 
will save, can you afford not to have one? 
Call us for your nearest dealer. 










PRACTICAL PERIPHERALS, INC. 

31245 LA BAYA DRIVE, WESTLAKE VILLAGE, CA 91362 • (213) 991-8200 




'Suggested retail price for either model. 



■ 



Editorial. 



James Martin, data-processing and futures expert, 
offers the following predictions about the role of the 
pocket terminal ten years in the future. The following 
excerpt is from his book, Telematic Society: A 
Challenge for Tomorrow (Prentice-Hall, 1981). 

Pocket terminals mushroom in sales and drop in 
cost as fast as pocket calculators did a decade earlier. 
Most people who carried a pocket calculator now have 
a pocket terminal. The pocket terminal, however, has 
an almost endless range of applications. It can access 
many computers and data banks via the public data 
networks. The pocket terminal becomes a consumer 
product (as opposed to a product for businesspeople) 
on sale at supermarkets, with human factoring that is 
simple and often amusing. The public regard it as a 
companion which enables them to find good restau- 
rants, display jokes on any subject, book airline and 
theatre seats, contact medical programs, check what 
their stockbroker computer has to say, send messages, 
and check their electronic mailbox. 

Public data networks are ubiquitous and cheap, and 
accessible from every telephone. Their cost is indepen- 
dent of distance within most countries. 



>i/W^ 



Smarter T 



nal. 



gives you the best of everything. From ergonomics to emulations 
i upgradable performance to user programmable features. New 
has one terminal had so much to offer to such a wide variety of users . . . 
.■ Therefore your Total Solution . . . 
Through user- selectable or optional changes the TS-1 Emulate 
Almost Any Terminal.,. 

is remarkable cost-efficiency with unbeatable performanr 
icence-proof design for today and tomorrow . . . 

unbeatable features . , . 
>ll 212 compatible modem/auto dialer (optional) 
. memory with horizontal scrolling to 256 columns (options 



ial attributes not stored on screen 
nMq graphics with 100 characters 



• 28 nonvolatile user- 
programmable function ' 

• Soft set up eliminates I 

patlbie gr 



Itii J BV FfKCO Oh I A PWDUCTS 




Falco 

DATA PRODUCTS 



1286 Lawrence 
Station Rd. 
Sunnyvale, 
CA 94086 
(408)745-7123 
Telex: 172494 



keep naive users from getting stuck.) 

You've probably gone through the usual tedium of 
identifying your terminal, hitting carriage returns, and 
going through all the usual make-work dialogue required 
to get onto databases. The Telecomputer eliminates all 
that. Once the Access Center downloads its protocols to 
your terminal, your terminal automatically completes the 
dialogue with, say, Dow Jones. You need only enter your 
password and you're instantly online. It takes only a cou- 
ple of seconds. If you regularly access several databases 
or electronic mail services, you'll appreciate not having 
to memorize a lot of annoying protocols. This sort of 
elegant engineering will help popularize computers. 

Another useful feature is the pair of speed-control 
keys, labeled SLOW and FAST, that control the speed at 
which text scrolls across the display by sending XON and 
XOFF control characters to the remote computer. Every 
time you press one of the keys the display incrementally 
slows down or speeds up. You can slow the display down 
to transcribe messages or speed it up to quickly scan 
through material. 

There's little more to add about the operation of the 
Telecomputer — it's that simple. The built-in autodialer 
remembers your local Tymnet and Telenet numbers after 
you enter them once. It even shuts itself off if not used for 
eight minutes, first giving you an audible warning. The 
machine is truly "goof-proof." 

Peripherals for the Telecomputer (see photo 4), includ- 
ing an acoustic interface (not the same as an acoustic 
coupler because the modem circuitry is already contained 
inside the Telecomputer — therefore the price is lower); a 
20-column thermal dot-matrix printer made by Olivetti; 
an RS-232C interface; and a video interface designed for 
use with both TV sets and video monitors, will be avail- 
able by July. 

Design Philosophy 

It's no surprise that the Telecomputer takes a human- 
factors approach. Its designers come from strong back- 
grounds in consumer electronics. Bob and Holly Doyle 
have invented more than a dozen computer toys, includ- 
ing Parker Brothers' best-selling Merlin and Stop Thief. 
While at Mattel Electronics, Jeff Rochlis supervised the 
production of the Intellivision personal computer and 
hand-held games such as Brain Baffler (to which the Tele- 
computer bears a coincidental resemblance). Rochlis's 
four design goals were to make the Telecomputer cheap 
(it will sell for approximately $500 to $550); portable; 
easy to use (meaning both ease of access to databases and 
ease of use via plain English dialogues); and secure. 

That last point deserves a volume in itself. Someone 
once said that today's electronic mail services are more 
like "postcard" services because the security measures are 
so lax that any half-competent programmer can crack 
them. The Telecomputer's three-way security keying sys- 
tem goes a long way to correcting this situation. The user 



16 April 1982 © BYTE Publications Inc 



Circle 177 on Inquiry card. 










THIS AD MARKED THE BEGINNING OF A NEW ERA 
IN MICROCOMPUTER PROGRAMMMG. 



It announced PEARL* 

PEARL ushered in the era where programmers could free themselves 
from boring, routine and repetitive tasks. Because PEARL handles 60-70% of 
programming details, which permits programmers to spend their time more creatively, 
and more productively. 

But that was two years ago. 

Today, there's Personal PEARL - to be introduced at the West Coast 
Computer Fair. And it goes a giant step further. Personal PEARL makes the 
capabilities of the computer available to virtually anyone. 

For its $295 price, even people without technical backgrounds can use 
it to visually create their own applications and reports on any computer. 

So the ad you're reading now is announcing an even more important 
breakthrough in computer and personal productivity. 

just fink about the RELATIONAL SYSTEMS INTERNATIONAL 

possibilities. 1 hen Contact OUr RQ Box 12892/Salem, Oregon 97309/ (503) 363*8929 

Personal PEARL Product Manager. 



Circle 355 on Inquiry card. 



CPU International is the former name of Relational Systems International. PEARL (Producing Error-Free Automatic RapiH Logic) 




Send today for our NEW full-color 
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checks, statements, invoices, stationery, 
envelopes, supplies and accessories. 
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Editorial. 



has a password, the terminal has a built-in password 
(unknown to the user), and the host computer has a pass- 
word. (This is the proposed standard. Presently, only the 
IXO Access Center computer adheres to it.) The host 
computer combines its password with both the user's 
password and the terminal password in complex, ran- 
domized ways to make it virtually impossible for some- 
one else to emulate your terminal with another terminal 
or computer, even if he knows your password. It's an ad- 
mirable approach to securing data. I hope manufacturers 
will pay serious attention to it. 

The Telegraphic Age 

Rochlis likes to compare today's computer age to the 
telegraphic age of the nineteenth century. In many ways, 
he says, the technique of talking to computers is still in its 
"telegraphic" stage. Back when the telegraph was the 
chief means for long-distance communication, telegraph 
operators were required as intermediaries for all trans- 
actions. Unfortunately, they "spoke" a different language 
than their clients: Morse code. Today, most of the public 
at large do not know how to operate computer terminals 
and must rely on computer operators. The latter are in ef- 
fect the most expensive "peripherals" of all. To bring 
computing power to the people, we must supply them 
with cheap and easy-to-use computers and terminals. 

There is a trend this year toward the development of 
briefcase-sized computers and terminals. (See the report 
about Epson's new HX-20 portable computer on page 
104. ) And that's just the beginning: watch for a series of 
new, small computers from both America and Japan. But 
size and cost alone will not guarantee the success of these 
machines with the general public. Human engineering has 
to be our paramount concern in the personal-computing 
field; the IXO terminal is a major step in this direction. 



Piracy Addendum 

Many people have asked me to comment on the issues 
of software piracy raised in Jerry Pournelle's January col- 
umn. (See "User's Column: Operating Systems, Lan- 
guages, Statistics, Pirates, and the Lone Wolf," January 
1982 BYTE, page 132.) My only comment is that, while I 
sympathize with many of the opinions expressed by 
Jerry's "mad friend" Mac Lean, my overall attitude 
toward copying software has not changed since I spoke 
out in the May 1981 editorial. Nevertheless, I think it's 
important to air opposing viewpoints in BYTE. The 
debate is healthy and being overly dogmatic serves no 
useful purpose. I'd like to hear more from readers about 
this issue. ■ 



18 April 1982 © BYTE Publications Inc 



Circle 293 on Inquiry card. 



Circle 285 on Inquiry card. 



This is all- you really need! 

An Apple n®, a printer, a video screen, a modem, a disk drive, 

CPS MultifuncticL 



The CPS Multifunction card and cables are all 
you need to connect almost any printer, mo- 
dem, or terminal to your Apple II®. It's really 
three cards in one. It provides the capabilities 
of a serial interface, parallel output interface, 
and real-time clocK/calendar. It saves you 
money, power, and slots. The CPS Multifunction 
is compatible with DOS, CPM, PASCAL, and 
BASIC. Suggested retail price $239, including 
software. Cables $24.95 each. 

1 Mountain Computer J 

■■■ 



The RAMPLUS+ card allocs you to expand the 
available memory of your Apple II® to 80K. 
RAMPLXJS+ has two 16K banks of RAM. The card 
is supplied with 16K of installed RAM, with an 
additional 16K of plug-in RAM available. It is 
compatible with DOS, CPM, PASCAL, and BASIC, 
also. Suggested retail price $ 189. Additional 16K 
RAM $24.95. 



398 EL 


PUE8LQ ROAD 


scans 


VflUEY.. CftUFOI 


9U9SS 




496 43H 


J-6638 


CPS mri 


.TIFUNCTIOH 


ftftHPtJU 


;+ 






^ 



* The modem is a product of 
Hayes Microcomputer Products, Inc. 
The video screen is a product of NEC. 
The printer is a product of Epson America. 
The Apple II"*' is a product of Apple Computer, Inc. 
The disk drive is a product of Apple Computer, Inc. 



Letters 



The Missing LINC 



I keep seeing the "personal computer 
era" referred to as having begun in the 
mid-1970s, as if it required the microchip 
to make it possible to design hardware 
and software for a single-user computer. 
But there are important antecedents to 
this, dating back twenty years, and they 
were not hand-held calculators so much as 
proper computers with analog interfaces 
and mass storage — namely, lab com- 
puters. 

In 1962, at MIT's Lincoln Labs, Wesley 
Clark and Charles Molnar designed the 
LINC (Laboratory INstrument Com- 
puter), to be used in a research lab in a 
manner analogous to an oscilloscope. It 
wasn't merely its display and analog-to- 
digital converters (hence joysticks and 
Spacewar) which made it unique: its soft- 
ware was designed to enable the scientist- 
user to program without a professional 
programming staff. Much of the design 
rationale was process-control oriented 
(hence interrupts) so that online data 
analysis could be performed during an ex- 
periment, allowing modification to the ex- 
perimental protocol. But having such a 
friendly computer in the room, shared 
only with the other users of the same lab, 
created the atmosphere of "personal com- 
puting" a decade before mass-market 
economics extended it. 

The first 24 LINCs (with their small 
memories and dual small-reel magnetic 
tapes— so-called LINCtapes — which were 
the forerunners of the floppies) were built 
under a government research grant and 
distributed around the country in 1963 to 
various physics, chemistry, and life 
sciences labs (they were especially impor- 
tant in my own field of neurobiology). 
With the plans in the public domain, 
several computer manufacturers began 
selling them (Digital Equipment Corpora- 
tion's version cost $54,000 — and in 1966 
dollars, at that) and improving on the 
design (DEC's LINC-8 and PDP-12 were 
the major extensions). In essence, 
thousands of users experienced the per- 
sonal computer revolution in the 1960s 
and helped shape its present philosophy. 

It is curious how this heritage has been 
forgotten in the great expansion. One con- 
sequence is an excessive amount of rein- 
venting the wheel. The interactive soft- 
ware packages developed by LINC users 



(especially at Washington University and 
the University of Wisconsin) were ex- 
cellent— I have yet to see a statistics-and- 
plotting package for microcomputers 
which equals LINDSY for the LINC, and 
the LINCs text editor and operating sys- 
tem (LAP) puts CP/M to shame. And— 
another forerunner of the present micro- 
computer situation— the really good 
general-purpose software came from small 
groups, not manufacturers. 

Most people tend to compare new 
microcomputer software to fancier main- 
frame versions, but it is often more ap- 
propriate to compare it to the lab com- 
puter antecedents, which shared a similar 
philosophy. It is the design philosophy for 
microcomputers that so sets them apart 
from the staffed mini- and main-frame 
computers, and it is that single-user-as- 
master philosophy that was so extensively 
developed by the LINC users. 

William H. Calvin, Ph.D. 

Associate Professor of Neurophysiology 

Department of Neurological Surgery 

RI-20 
University of Washington 
Seattle, WA 98195 



Computer Scrabble * 

We were pleased to see an article dis- 
cussing the feasibility of a computer op- 
ponent for Selchow & Righter's popular 
Scrabble word game (see "Computer 
Scrabble," December 1981 BYTE, page 
320). Others who are intrigued by this 
concept will appreciate knowing that the 
state of the art in microcomputer Scrabble 
has made a great leap forward. It is far 
beyond the boundaries that Mr. Roehrig 
tells us will not be broken by anything less 
than a new, superior generation of micro- 
computers. 

"Monty plays the Scrabble Brand 
Crossword Game" (a computer-opponent 
program available on disk for the Apple II 
and TRS-80 Models I and III from Ritam 
Corporation for $39.95) demonstrates 
both speed and ability, within the con- 
straints of today's microcomputers. 

Monty spends an average of only 4V2 
minutes per move at the highest skill level, 
and yet it uses an extensive word list (over 
50,000), based in part on the Official 
Scrabble Players Dictionary. 



As for memory, the program requires 
no more than 48K bytes for Apple and 
32K bytes for TRS-80 versions, much of 
which is devoted to machine-language 
graphics, music, and other user-interface 
requirements. The dictionary is accessed 
from disk and is stored in an average of 
only two bytes per word (with an average 
length of 6 or 7 letters) by use of advanced 
compression techniques. In addition, 
Monty is capable of challenging other 
players' words, based on linguistic anal- 
ysis, without accessing the disk. 

To give Mr. Roehrig's efforts due 
credit, the "game's complexities" do offer 
a challengel It took us several major 
design breakthroughs, over four man- 
years of programming (for three different 
computers), and a lot of determination to 
develop "Monty plays Scrabble" without 
conceding to "certain constraints" on 
word length, search, and placement. 

Although his conclusion that "im- 
proved computerized Scrabble will re- 
quire a faster host computer with more 
memory capacity" has been disproved by 
example, we thank Mr. Roehrig for his ar- 
ticle. It makes our endeavor seem quite 
worthwhile when we learn that we've 
achieved the impossible! 

By the way, Mr. Roehrig neglected to 
properly acknowledge that Scrabble is a 
trademark of the Selchow & Righter Com- 
pany, and to disclaim, as does Ritam, any 
sponsorship or endorsement by Selchow 
& Righter. 

Robert Walls, President 
Ritam Corporation 
POB 921 
Fairfield, IA 52556 

* Scrabble is a registered trademark of 
Selchow & Righter Company. We apolo- 
gize for not acknowledging this in a prior 
article. . . . MH 



More Commbat 

I would like to thank George Stewart 
for his excellent and perceptive review, 
"Commbat: A Tele-Game for Two," in 
the December 1981 BYTE (page 100). He 
captured my motivation for creating 
Commbat in the first paragraph. 

The problems he mentioned of synchro- 
nizing both systems upon initial start-up 



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Letters. 



and keyboard sluggishness are a result of 
accommodating the TRS-80 Model Fs 
RS-232 port. It cannot interrupt the pro- 
cessor when it has a character, so it must 
be operated in a polled-loop configuration 
in order not to lose data. As long as 
Model Is or their look-alikes are a signifi- 
cant part of the market this problem' will 
be necessary. I believe the first release of 
Commbat was the one reviewed. As a 
result of the synchronization problem, the 
current release, Commbat Version 2.1, 
has a split-screen dumb-terminal option 
that is presented to the user upon start-up. 
This mode can be entered without any 
particular worries as to timing by both 
participants, and when both are com- 
municating they can exit to the game. This 
mode also allows communications to be 
established through some of the dial-up 
services that can handle pass-through 
communications between users. 

At last report, the Atari version of this 
game was in production and should be 
available soon from Adventure Interna- 
tional, and an Apple version is on the 
way. The major feature of these different 
versions is that they will all play against 
each other. My intention is to keep 
Commbat system independent; as other 
systems become a significant portion of 
the market they will get their own com- 
patible version. Anyone who buys 
Commbat will be able to play anyone else 
who has ever bought it, regardless of 
equipment. 

The second game of this planned series 
is finished and will be marketed in the 
near future, and the third is coming along 
well. 

Robert A. Schilling 
725 SE Vance Circle 
Palm Bay, FL 32905 



No Contest 



Despite the "battle" for dominance por- 
trayed in the "Unix vs. CP/M" item in the 
November 1981 BYTELINES column 
(page 306), the position of the apologists 
for CP/M has become all but untenable. 
The implication that Unix and CP/M can 
be compared on the same terms is wholly 
misleading. Unix is a full-featured operat- 
ing system which is widely regarded as the 
finest ever written, while CP/M is little 
more than a program loader. 

The only reason for the continuing 
popularity of CP/M is summed up in the 



column's last sentence: "CP/M appears to 
have much more public-domain and com- 
mercial software for it than does Unix." 
As the computer community recognizes 
that Unix is bound to become the'standard 
16-bit microcomputer operating system, 
commercial applications software for it 
will inevitably begin to appear. And, 
since most Unix software is written in the 
powerful C programming language rather 
than in assembly language or some dialect 
of BASIC, we can be sure that the com- 
mercial software which will eventually be 
available under Unix will be of higher 
quality than that found in the CP/M 
market. 

John Lynn Roseman 
Urban Software Corporation 
11 West 34th St. 
New York, NY 10001 



Toward a Structured 
Assembler 

I have just finished reading the two-part 
article "Toward a Structured 6809 Assem- 
bly Language" (November 1981 BYTE, 
page 370, and December 1981 BYTE, page 
198). I found the article quite interesting, 
especially since I have been selling a struc- 
tured assembler (STASM09) package 
since 1980. STASM09 uses a pre-/post- 
processor to generate the appropriate in- 
ternal labels and to modify the listing to 
provide automatic indentation of the 
listing. (The indentation of the code pro- 
vides graphic display of the structure of 
the program module.) 

STASM09 provides the IF. . .ELSE. . . 
ENDIF but not the WHILE. . .ENDWH or 
REPEAT. . .UNTIL constructs described 
by Mr. Walker in his article. Instead, 
STASM09 provides a more general 
DO. . .ENDO construct with several 
methods to BREAK out of the loop. This 
allows both the WHILE and REPEAT 
functions to be implemented. In addition, 
STASM09 provides a COUNT function 
that can be used to control the number of 
times a loop is traversed. 

STASM09 is designed to run under the 
FLEX operating system from Technical 
Systems Consultants rather than the more 
industrially oriented Motorola operating 
system. STASM09 is available on a 
5V4-inch, single-density disk for $49.95, 
including shipping and handling, from 
Sansaska Systems, 3311 Concord Blvd., 
Concord, C A 94519. 



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Letters 



Incidentally, I have noticed a possible 
problem with the macros defined in part 2 
of the article. When an error condition is 
recognized in a macro, a long branch to 
the EXBUG monitor is inserted into the 
code. Since this can occur in code that is 
entirely relocatable, the relative offset of 
this error jump will be wrong any time the 
program is relocated. If this happens, the 
results will be entirely unpredictable and 
possibly very hard to debug. 

Derek Gitelson 
Sansaska Systems 
3311 Concord Blvd. 
Concord, CA 94516 



A Recipe for Standards 

I have been involved with the micro- 
processor standards work of the IEEE (In- 
stitute of Electrical and Electronics 
Engineers) Computer Society from its 
beginning (August 1977), so Chris 
Morgan's editorial in the November 1981 
BYTE caught my eye. The question is 
"Can we agree on standards?" The correct 
answer is a qualified "Yes," and the 
"heated debate" usually occurs only when 
that qualification is violated. 

What is this qualification? The standard 
must be done right. The right way to 
establish a standard, once the need for a 
standard is apparent, requires three steps: 

• First define the objectives of the stan- 
dard that the potential users can agree on. 

• Examine the marketplace to see if there 
exist any widely accepted products that 
are designed to specifications that meet or 
are near the objectives. This examination 
can go four ways: (1) if there are no prod 
ucts, establish a design team of competent 
technical people to design specifications; 
(2) if there is one product fully meeting the 
objectives, adopt its specifications; (3) if 
there are one or more products close to 
the objectives but in some way inade- 
quate; establish a design team to adopt 
one (impartially, if possible) and to pro- 
duce from it adequate specifications; (4) if 
there are several incompatible products 
whose specifications fully meet the objec- 
tives, establish an impartial selection 
board to choose one set. (In this case it is 
usually too late to define a standard, but 
sometimes the need for it will reshape the 
marketplace.) 

• Write the specifications into a draft 
standard and take it out for public review. 
This is a necessary safeguard against per- 



26 April 1982 © BYTE Publications Inc 



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Letters, 



sonal bias and technical incompetence in 
the designers. All responses to this review 
step must be dealt with before the stan- 
dard can be established. The draft stan- 
dard need not be modified for every re- 
sponse, since some of them will them- 
selves be biased or incompetent, but all 
responses must be considered. 

The American National Standards In- 
stitute (ANSI) and the IEEE, as a member 
of ANSI, are set up to develop standards 



by these procedures, and the standards so 
developed do receive wide public accep- 
tance. Although it is still being reviewed 
and revised, the proposed standard for the 
S-100 bus is an example of such success. 
What about the wrong way? Usually it 
is some variety of "Let's standardize on 
my way of doing it." A lot of standards 
are proposed this way, and some actually 
succeed. If they succeed, it is in spite of 
the attitude, not because of it, and then 
only because the proposer has done the 





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The WORD will look up the correct 
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The WORD analyzes your writing, 
counting words and showing you how 
often each word was used. 

The WORD has a special homonym 
helper feature to deal with these pesky 
words. 

The WORD will find rhyming words, 
solve crossword puzzles, and much more! 

CALL TODAY! 

(714)291-9489 



technical homework and controls the 
marketplace (for example, IBM, which is 
known for this attitude). 

How does DIF fit in? [Editor's Note: 
DIF, for Data Interchange Format, is a 
method for representing data in a pro- 
gram so that it can be transported directly 
to other programs. See "DIF: A Format 
Between Applications Programs" by Can- 
dace E. Kalish and Malinda F. Mayer, 
November 1981 BYTE, page 174.1 Soft- 
ware Arts is promoting DIF as a standard, 
using the "let's do it my way" approach. It 
may succeed at this, because Visicalc hap- 
pens to dominate the market. It may even 
be that DIF is a good technical proposal, 
but we cannot know this without the pro- 
per review procedures, which Software 
Arts has bypassed. 

I think it is unfortunate that monopoly 
industries like IBM and Software Arts can 
wield such Machiavellian powers as to im- 
pose on the rest of the world standards 
like EBCDIC (extended-binary-coded- 
decimal interchange code) and (possibly) 
DIF without the benefit of good technical 



Tom Pittman 

Itty Bitty Computers 

POB 23189 

San Jose, CA 95153 



/ concur with Mr. Pittman s rational ap- 
proach to the establishment of a standard. 
However, our industry does not always 
behave rationally. I take issue with the 
implication that IBM and Software Arts 
are necessarily Machiavellian or even 
monopolistic. To be monopolistic, by 
definition a company must have exclusive 
control of the means of producing a pro- ■ 
duct or service. Visicalc may be the best- 
selling microcomputer program of all 
time, but that hardly excludes competitors 
from offering their own types of spread- 
sheet programs. In the case of IBM, what- 
ever its past record has been in the main- 
frame market, its behavior in the personal 
computing market has been remarkably 
open and nonmonopolistic, if I may use 
that term . . . CM 



Multicolored Players, or 
The Atari Tutorial Debated 

I enjoyed reading Chris Crawford's 
'The Atari Tutorial, Part 3: Player- 
Missile Graphics" in the November 1981 



28 April 1982 © BYTE Publications Inc 



Systems Group System 2800 
computers. They're making 
people stand up and take notice. 

But then Systems Group 
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That same effort has made 
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Select CP/M! MP/M'or 
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f rcgisrcrcd Trademark of Dieiral Research 
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1981 

Today's Requirements 

Dual floppy single or multi-user system 



1983 



1985 



Tomorrow's Requirements 

10M byte hard disk and floppy drive, 
single or multi-user system 



Your Future Requirements 

40M byte hard disk and 20M byte tape 
back-up, single or multi-user system 



Circle 313 on inquiry card. 



\trryx 
software 

What does the Oryx, an African antelope, have 
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Oryx Software wants to bring trustworthy ser- 
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To celebrate our opening, we will absolutely 
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ORDER TOLL FREE • Outside Wl 
1-800-826-1589 



SOFTWARE 

Graphpower 299.00 

Tax Preparer '82 127.00 

Real Estate Analyzer 127.00 

Creative Financing 127.00 

Word Processor 1 425.00 

Financial Projection 550.00 

Mail Management 250.00 

Micropro Wordstar ... 248.00 

Mailmerge 90.00 

Spellstar 169.00 

Supersortll 159.00 

Context Connector 1 80.00 

Easywriter (Pro) 195.00 

Easymover 45.00 

Tellstarll 70.00 

Easymailer 160.00 

Oatadex 249.00 

Microplan Basic. 419.00 

Executive Secretary 212.00 

Nevada CoBol 129.00 

Visicalc (3.3) 209.00 

Apple Panic 25.00 

SpellGuard 239.00 

Computer Air Combat 53.00 

PFS & Report 80.00 

Sublogic Flight Simulator 28.00 

SpeedStar 115.00 

Systems Plus Acc'tg. Module 425.00 

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Painter Power 34.00 

Invoice Factory 1 48.00 

Locksmith 99.00 

Raster Blaster 25.00 

SuperCalc 269.00 

Visiterm 88.00 

Visiplot 165.00 

Visidex : 209.00 

Visitrend/Visiplot 249.00 

Magic Window 79.00 

Int'l Grand Prix 25.50 

Estimator 295.00 

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Graphic Software 19.00 

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Electronic I, II, or III 39.00 

WordPro 3+ 295.00 

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For Peripherals see our other ad, page 382 



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• Wisconsin residents ■ add 4% sales tax 

• Foreign orders - please add 15% 

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TOLL FREE ■ Outside Wisconsin: 
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For Technical Info & in Wisconsin: 
715-848-2322 
Oryx Software Dept. A. 

P.O. Box 1961 • Wausau, Wl 54401 



30 April 1982 © BYTE Publications Inc 



S0 



Letters. 



BYTE (page 312). I believe, however, he 
has made an error. On page 319 he stated 
that multicolored players are not possible 
unless you use display-list interrupts. On 
the contrary, there is a way to produce 
multicolored players in BASIC very easi- 
ly. If you look on page III. 7 of the Atari 
Hardware Manual, you will see that set- 
ting the fifth bit of GPRIOR ($26F) at 
location 623 decimal will cause a logical 
OR function of the colors of player with 
player 1 and player 2 with player 3. The 
result is a choice of three colors in the 
overlapped region. The following pro- 
gram demonstrates this effect: 

10 A=PEEK(106)-8:POKE54279,A:REM 

SET UP PLAYER - MISSILE GRAPHICS 
20 POKE 559,46:POKE 53277, 3:REM 

DOUBLE -WIDTH RESOLUTION 
30 POKE 704,26:POKE 705, 102:REM 

PLAYER & 1 COLORS 
40 PMBASE = 256*A + 512 
50 FOR l=0TO256:POKE 

PMBASE+l,0:NEXT I 
60 FOR I = TO 7:READ A:POKE 

PMBASE + 48 + l,A:NEXT I 
70 DATA 255,255,195,195,195,195,255,255 
80 FOR I = TO 7:READ A:POKE 

PMBASE+176+I,A:NEXT I 
90 DATA 60,60,60,60,60,60,60,60 
100 L=100:R=148:POKE53248,L:POKE 

53249, R 
110 FORT = 0TO1000:NEXTT 
120 FOR 1 = 1 T0 24:L=L+1:R=R-1 
130 POKE 53248, LPOKE 53249, R:NEXT I 
140 FOR T = 0TO300:NEXTT 
150 POKE 623,32:REM SET BIT 5 OF 

GPRIOR 
160 GOTO 160 

Lines 50-100 POKE the player images 
into the player graphics buffer and set 
their horizontal positions. Lines 110-160 
let you see the player images coming 
together and then the three colors being 
produced as one player. Remember that 
to move this three-colored player requires 
you to POKE the same horizontal position 
into the horizontal-position registers of 
both player and player 1. 

Peter Hecke 
767 Bergen Blvd. 
Ridgefield, NJ 07657 



Chris Crawford replies: 

Thank you for your program; it dem- 
onstrates the OR function of GPRIOR bit 
5 very well. This technique, however, 
does not create a multicolored player. In- 
stead, it creates a three-colored object us- 
ing two players — certainly a useful tech- 
nique for "getting more for your money" 
with two players. If you are not otherwise 



using all your players, you can create a 
multicolored object by overlapping 
several players of different colors. With 
the technique you describe, you can get 
seven colors (the normal five plus two 
"overlap" colors), although you do not 
have full control over the overlap colors; 
without this technique, the most you can 
get is five colors (if you use all four 
players and the missiles as a fifth player). 

The method I referred to in my article 
modifies the display list to execute an 
assembly-language display-list interrupt 
routine to change the color register of a 
given player while the video image is be- 
ing drawn. This technique can produce 
one player that has multiple colors, but it 
has two disadvantages: first, it can only 
produce images striped horizontally with 
different colors; and second, unless you 
change the display list on the fly, the 
multicolored player cannot move vertical- 
ly (display-list interrupts are tied to a cer- 
tain horizontal line of the video display). 

Thanks for sharing your letter and pro- 
gram with other BYTE readers and me. 



Wanted: Education In 
Computerized Business Systems 

Students interested in obtaining a 
university education in the development 
of business-oriented computer systems 
should investigate the programs offered 
by the business schools. Paul Brady in his 
article on "Bridging the 10-percent Gap" 
(see the October 1981 BYTE, page 264) 
identifies the need for this type of train- 
ing, which combines courses on com- 
puters with courses on business organiza- 
tions and management skills. However, 
his comments do not indicate that such 
programs already exist. Rigorous com- 
puter science programs provide excellent 
technical and theoretical training but are 
not typically designed to produce busi- 
ness-systems analysts and application pro- 
grammers. For further information on the 
educational issues involved and a survey 
of programs offered, see the article by Jay 
F. Nunamaker Jr., "Educational Programs 
in Information Systems," Communica- 
tions of the ACM, March 1981, and the 
in-depth report on "the DPMA Model" in 
Computerworld, September 21, 1981. 

Hugh Howson 

Professor Invite 

Universite du Quebec a Montreal 

Case postale 8888, Succursale "A" 

Montreal P. Q.H3C3P8 ■ 



A simple fact: 



The considerable 
benefits of a per- 
sonal computer like 
the Osborne 1® are 
often intangible, 
often exciting, and 
always expanding. 

The value of the 
Osborne 1 is clear 
and simple: 
$1795. Complete. 



$1795 includes this 
hardware: 

Z80A™ CPU with 64K RAM □ 
Dual floppy disk drives with 100K 
bytes storage each □ 5" CRT □ 
Business keyboard with numeric 
keypad and cursor keys □ 
RS-232C Interface □ 
IEEE 488 Interface □ 
Weather-resistant, portable 
housing □ Operates on European 
and American voltages □ 



$7795 includes this 
software: 

D CP/M® Operating System 

□ WORDSTAR® word 
processing with MAILMERGE 

□ SUPERCALC™ electronic 
spreadsheet 

□ CBASIC® 

□ MBASIC® 




Available at your local computer retailer. 



Trademarks: Z80A: Zilog Corporation 

SUPERCALC: Sorcim Corporation 

Registered Trademarks: 

OSBORNE I: OsborneCompuler Corporation 

CP/M: Digital Research MBASIC: Microsolt 

CBASIC: Compiler Systems. Inc. 

WORDSTAR. MAILMERGE: MicroPro International 



The Generic Word Processor 

A word-processing system for all your needs. 



You 11 be amazed by this product's versatility. 



Congratulations on your purchase 
of the GWP Inc. Generic Word- 
Processor System. We are sure that 
you will find this word processor to 
be one of the most flexible and conve- 
nient on the market, as it combines 
high unit reliability with low operat- 
ing costs and ease of maintenance. 

Before implementing the system, 
carefully study figure 1 to familiarize 
yourself with the main features of the 
GWP word-processing unit. 

Initialization 

The word-processing units supplied 
with your GWP are factory-fresh and 



Editor's Note: Once in a while 
we come across a product that's so 
useful we feel compelled to bring it to 
our readers' attention. The Generic 
Word Processor System (GWP) is such 
a product, incorporating the essentials 
of a word processor in a sublimely sim- 
ple form. 

With the manufacturer's permission, 
we are reprinting the documentation 
for this product. After working with 
the GWP for several weeks, we're de- 
lighted by the feeling of total control 
that the system gives us and are certain 
you will be too. No more accidentally 
erased files, no damaged disks, no 
hardware problems . . . SJW. 



Philip Schrodt 

Department of Political Science 

Northwestern University 

Evanston, IL 60201 

uninitialized. Before they can be 
used, they must be initialized using 
the GWP initialization unit (see figure 
2). Because of the importance of this 
unit, we designed it with a distinctive 
shape so that it will not be misplaced 
among the voluminous vital papers 
on your desk. 

To initialize a word-processing 
unit, carefully place the character in- 
sertion subunit into the left side of the 
initialization unit and rotate the 
word-processing unit approximately 
2000 degrees clockwise while exerting 
moderate pressure on the word-pro- 
cessing unit in the direction of the in- 
itializer. Check for successful in- 
itialization by attempting a character 
insertion. If the insertion fails, repeat 
the initialization procedure. The 
word-processing unit will have to be 
reinitialized periodically; do this 
whenever necessary. {Warning: do 
not attempt to initialize the word- 
processing unit past its character dele- 
tion subunit. Doing so may damage 
both the word processor and the 
initializer.) 



Operating the Word Processor 

The GWP can perform all the basic 
functions featured in word processors 
that cost thousands of dollars more. 
Furthermore, because the GWP does 



not require electricity, it can operate 
during power blackouts, electrical 
storms, and nuclear attacks. By con- 
serving precious energy resources, it 
helps free our beloved country from 
the maniacal clutches of OPEC. 

Basic functions of the word pro- 
cessor are listed below: 

Inserting text: Use the character- 
insertion subunit to write in the 
words you wish to insert, applying 
moderate downward pressure to the 
unit. Be sure to write clearly so that 
the typist can follow what you have 
written. 

Deleting text: With moderate 
downward pressure, rub the charac- 
ter-deletion subunit across the text to 
be deleted. Repeat this procedure 
several times. The text will gradually 
disappear, whereupon you will be 
able tb insert new text. 

Underlining: Using the character- 
insertion subunit, place the unit 
slightly below and to the left of the 
first character you wish to underline. 
Move the unit to the right until you 
reach the last character to be under- 
lined. 

Bold face: Repeat the text-insertion 
procedure twice, pressing downward 
with greater pressure than you would 
normally apply. 

Move to beginning of text: With 
the text you are working on in hand, 



32 April 1982 © BYTE Publications Inc 



"Adding manpower to a late 
software project makes it later." 

Brooks' Law: The Mythical M 



Brooks' Law: The Mythical Man-Month 







Don't waste man-months: Try CRTFORM. 



Programming deadlines aren't met by adding more 
programmers to the job, but you can increase 
productivity, and reduce errors, by giving pro- 
grammers the tools they need. 

CRTForm is a program which produces an interface 
between the programmer and the end user. It saves 
time by: 

• Gathering application program specifications. 

• Providing friendly and consistent runtime 
communication with the end user. 

• Implementing CRT screen handling code. 

• Assuring programmers that the information 
which they receive is correct. 

• Allowing screen modifications and specifica- 
tion changes without requiring recompilation 
of application code. 

If you're writing applications code then CRTForm 
can save you time, as well as reduce errors and 
provide a terminal independent solution to your own 
custom programming problems. 



The CRTForm system contains: 

• A forms manager that manipulates a random 
access file of input specification forms. 

• An editor that creates and modifies the 
specification forms. 

• A print utility that produces hard copy of 
forms and their specifications. 

• A terminal-independent runtime module in 
the machine language of your host processor. 

• A code generator that writes source code 
skeletons in Pascal, FORTRAN, COBOL, 
PL/I, BASIC, C, and even (for advance 
planning purposes) Ada. 

CRTForm is available for most micros and minis 
running under the CP/M-80, CP/M-86, UCSD, 
RMX-86 and Apple Pascal operating systems. Stat- 
com will soon be releasing CRTForm under UNIX 
for both the 68000 and Z8000 processors. 

Please call or write for father information on OEM 
licensing arrangements, or for information about 
St&tcom's other productivity tools. 



PROGRAMS WRITING PROGRAMS 



CORPORATION 
57BB BALCQNES SUITE 202 AUSTIN TEXAS 78731 PHONE 512/<451-0221 



Staieom and CRTForm are trademarks of Siatcom Corn. Other Trademarks us follows: CP/M— Digital Research; UCSD-UC Sun Dieco: RM.X-Jnteh UNIX— Western Klct'iric: Apple — Annie Co: 68000— -Motorola: Z8000— Zilos 



CHARACTER DELETION 
SUBUNIT 




CHARACTER INSERTION 
SUBUNIT 



Figure 1: The GWP System word-processing unit is composed of the character-insertion 
subunit (at right) and the character-deletion subunit (at left). 




INITIALIZATION UNIT 

Figure 2: The word-processing initialization unit, which should be operated over a 
wastebasket. 





PASTE 

NON-TOXIC 
AGES 6-12 



Figure 3: The block text extraction and replacement units, commonly run in unison. 



AMHARIC 



HIEROGLYPHICS 



m s\ 



^T43Qai^D93i 



Figure 4: Sample type fonts illustrating the wide variety available with the GWP 
System. The manufacturer claims that if a language can be written, the GWP System 
can be adapted to it. 



move the unit to the beginning of the 
text. 

Move to end of text: Take the text 
you are working on and move the 
unit to the end of the text. 

Moving blocks of text: Block 
moves require use of the block text 
extraction unit and the block text re- 
placement unit pictured in figure 3. 
By means of the block text extractor 
unit, sever the paper immediately 
above and below the text you wish to 
move. Instructions for operating the 
extractor unit are etched on the side 
of the unit in Korean. If you still have 
difficulty operating the unit, call our 
service department for consulting 
help at our introductory fee of $50 
per hour, or ask any 5-year-old child. 

After separating the text to be 
moved, open the lid of the block text 
replacement unit and, grasping the 
block text replacement medium appli- 
cation unit, spread the block text re- 
placement medium on the back of the 
text. Move the text to the new loca- 
tion and affix it to another sheet of 
paper with gentle but firm pressure. 
In a few minutes, your text will be 
permanently affixed in the new loca- 
tion. 

Other Features 

Page numbering: After writing 
your entire text, inscribe a 1 on the 
first page, a 2 on the second page, etc. 
When you finish, all of the pages will 
be numbered. 

Centering: Determine where the 
center of the page is by looking at it. 
The center is usually near the middle 
of the page. Place the text to be 
centered evenly on each side of the 
center. It is now centered. 

Special fonts: The GWP System is 
extremely versatile and easily adap- 
table to specialized type fonts such as 
Sanskrit, Amharic, and hieroglyphics 
(see figure 4). You will find these 
fonts valuable in business corre- 
spondence, particularly if you are in 
frequent contact with Vedic gurus, 
Egyptologists, or Ethiopian Airlines. 

Saving files: Put the work you have 
finished in a safe place, one where 
nobody will find it or spill coffee on 
it. If it is not disturbed, it will be there 
when you return. 



34 April 1982 © BYTE Publications Inc 



k 



PRINTER INTERFACE 

Fr . ir Computer from the Mundahe-^^ 



hm i - eing able to use your 
computer seconds after beginning an 
extensive printout. 

Visualize your printout with page 
breaks, page numbering and titles, 
margins of your choice, indented 
carryover lines, on any size paper! 

Appreciate the time and money you 
will save by hot waiting on your 
printer. 

SooperSpooler, a buffered printer 
interface, maintains control over your 
printer while you go on using your 
computer for more productive 
activities. Eliminate waiting while 
your printer pecks through a long 
document. SooperSpooler accepts 
information from your computer at up 
to 2500 characters per second and 
feeds it to your printer as fast as it can 
handle it — without using any of your 
computers memory or time! As soon 
as SooperSpooler has stored your 
document in its buffer, control of your 
computer is returned to you. 



SopperSpooler features include: 

16K Memory— -Will handle most of 

your printing jobs (expandable, see 

options) 

Buffer Status Readout— Lets you 

know just how much data is stored 

Space Compression— Makes the 

best use of memory on columnar 

documents 

Pagination — Eliminates printout on 

page perforations 

Page Stops — For single sheet 

printouts 

Headers and Page Numbering — 

Give your listing a professional look 

Indentation on Carryover Lines — 

Easy to find the beginning of a line 

Self Test Routine — You instantly 

know that all is well 

All Features Software Controllable 

— Your program can take over 

Plugs into Most Computer 

Systems — Standard cables available 

$349.00! — 16K parallel I/O unit 



Options: 

• Serial Board— $95.00— Gives you 
the option of any combination of 
serial or parallel input or output. Can 
also be used for modem transmission . 

• Memory Expansion — -$159.00 — 
Additional 46K for a total of 62K 

• Cables— Available per your 
application. 

TM 

SooperSpooler by Compulink 
— The missing link that gives 
your microcomputer 
mainframe printing. 

COMPULINK 

CORPORATION 






1840 Industrial Circle, Dept. A 

Longmont, CO 80501 

(303)651-2014 

Order line: 800-525-6705 

Dealer inquiries welcome 

Circle 96 on inquiry card. 



POWER 




SooperSpooler 

INTELLIGENT PRINTER INTERFACE 



BUFFER STATUS 



RESET 



^ 





• 


• 

SPACE 
COMPRESSION 


o 

PAGE 



-<f 



n 







We accept 


• Checks 


Add $3.00 per order for postage and handling 


• VISA 


• Money Orders 


COD add $3.00 


• MasterCard 


• COD 


Colorado residents add sales tax 



Prices and Specifications Subject to Change 
Without Notice 



Deleting files: Take any files you 
no longer need and deposit them in 
the wastebasket. They probably will 
be gone in the morning. In most of- 
fices, this can also be accomplished 
by leaving the files in the open, for- 
getting to remove them from the 
copying machine, or writing CON- 
FIDENTIAL on the file in bold letters. 

Appending files: Place the first file 
on top of the second file. Treat the 
two files as though they were one file. 

Justification:Most word processors 
have little justification. This word 
processor has no justification at all, 
as it does not even lend prestige to the 
office where it is used, which is the 
justification for most word 
processors. 

Printing Files 

A printer for the GWP must be 
purchased separately. For conve- 
nience of operation, we recommend 
an ordinary typewriter and a typist. 
Give the text to the typist and tell him 
or her to type it. Printing speed can 
be improved by increasing the wages 
of the typist, threatening to withhold 
the wages of the typist, kidnapping 
pets, plants, or children of the typist, 
instigating intimidating tactics, and 
other conventional office-personnel 
management techniques. Printing 
speed can be decreased by asking to 
see the text, making continual 
changes in the text, asking the typist 
to answer the phone, decreasing the 
typist's wages, and installing a con- 
ventional electronic word processor. 
You will soon learn to adjust the 
printing speed to the optimal level for 
your particular needs. 

Copyright © 1981, Generic Word 
Processing Inc., Skokie, IL 60076 

(WARNING-.This system and ac- 
companying documentation are fully 
protected under the provisions of the 
Galactic Copyright Convention, ser. 
B, Rigal system, Code 56-*ADF6 
45932030: f. Duplication is strictly 
prohibited without the permission of 
copyright owner. Violators will be 
prosecuted to the fullest extent of the 
law or devoured at the discretion of 
the copyright owner or such agents as 
the copyright owner may choose to 
designate.) ■ 



CompuView 



New! 
CP/ M 86 For 

IBM! PERS ^ NAL COMPUTER 

The first available implementation of CP/M-86 for 
the IBM Personal Computer has the features needed to run 
the full range of CP/M-86 application programs. Included 
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driver which can emulate most popular CRT terminals, 
and double density 193K/drive disk capacity. The Tecmar, 
Inc. Winchester hard disk & other peripherals are also 
supported. 

Innovative features include built in horizontal 
scrolling and screen line editing which lets the user 
extensively edit or re-enter any line on the screen for 
CP/M and application programs. Besides editing the line 
being typed in, the cursor may be moved to any line on 
the screen, and the line edited by overtyping or inserting 
and deleting characters. Typing the 'Return' key will then 
send the line, as it appears on the screen, to CP/M. While 
common on mainframe systems, this screen line editing is 
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necessaiy due to mistyped or repeated commands. 

CompuView CP/M-86 for IBM Personal Computer. . . $325 
VEDIT-86 with above purchase $100 

8086 Software 



• VEDIT full screen editor for CP/M-86, SCP 86-DOS, 
IBM Personal Computer and IBM Displaywriter. Disk and 



Manual 



$195 



• CP/M-86 BIOS for popular S-100 disk controllers and 
SCP 8086 computer. Source Code $90 

V-COM Disassembler 

Finally a Z-80 disassembler for CP/M which produces 
easy to read code, a cross reference table and handles 
INTEL and ZILOG mnemonics. V-COM is exceptionally fast 
and produces an ASM file directly from a .COM file. 
V-COM can accept two user created information files. One 
contains assignments of labels to 8 and 16 bit values; the 
second specifies the location of tables and ASCII strings. 
The resulting .ASM file will then contain labels and proper 
storage allocation for tables and strings. Each information 
file may contain nested 'INCLUDE' to other files. Each 
package includes a 30 page manual, sample program files 
and variations of V-COM compatible with the TDL, MAC 
and two types of ZILOG assemblers $80 



36 April 1982 © BYTE Publications Inc 



Software An Industry Standard for CP/M & 8086 




Uniquely 
User Oriented 

VEDIT is user oriented to make 
your editing for program development 
and word processing as fast and easy 
as possible. The customization 
(installation) process makes VEDIT 
the only editing package that allows 
you to determine your own keyboard 
layout and use any available cursor 
and function keys. Just think of the 
difference it makes in your ease of 
learning and usage to type cursor and 
function keys instead of memorizing 
obscure control characters. This 
customization is menu driven, extends 
to much more and takes only a few 
minutes. 

Unequaled 
Hardware Support 

The CRT version directly 
supports over 35 terminals (including 
ANSI standard) in its installation 
menu and utilizes 'smart' terminal 
features such as line insert/delete, 
reverse scroll, status line and reverse 
video. Function keys on terminals like 
the Televideo 920/950, Heath H19, 
and IBM 3101 are. all supported. The 
memory mapped version is extremely 
flexible, supports bank select such as 
on the SSM VB3 and screen sizes up 
to 70 X 200. 



Sophisticated 
Full Screen Editing 

VEDIT gives you true 'what you 
see is what you get' full screen editing 
with an extensive set of features for 
creating and editing standard text files 
of up to one diskette in length. Very 
large files are effortlessly handled by 
VEDIT's ability to edit up to 47K of a 
file entirely in memory without 
performing any slow and annoying 
disk accessing. And you can handle 
multiple files, insert a specified line 
range of another file anywhere in the 
text and even change diskettes. 

User Oriented 
Features 

You get the features you expect, 
like searching, a scratchpad buffer for 
moving and rearranging sections of 
text, complete file handling on 
multiple drives and flexible macros. 
For easp of use VEDIT has features 
you won't find elsewhere, like 
automatic indenting for use with 
structured languages such as Pascal 
and PL/I. You are less likely to make 
a mistake with VEDIT, but if you do, 
one key will 'Undo' the changes you 
just made to a screen line. And if 
you run out of disk space with VEDIT, 
you can easily recover by deleting old 
files or even inserting another diskette. 
It is therefore no surprise that VEDIT 
is the industry standard for program 
development editing. 



Word Processing 

VEDIT is suitable for simple 
stand-alone word processing, or it 
may be used in conjunction with a 
text processor. Its features include 
word wrap, adjustable left margin, 
reformatting of paragraphs, word 
oriented cursor movement and 
deleting, and imbedding of printer 
control characters. VEDIT can print 
any portion of your file and display 
the cursor's line and column 
positions. 



Now for 

IBM 

Personal Computer 

XEROX 820 



Ordering 



Please specify your micro- 
computer, video board or the CRT 
terminal version, the 8080, Z80 or 
8086 code version and disk format. 

VEDIT - Disk and manual 

For 8080 or Z80 $145 

For CP/M-86 or IBM MDOS . $195 

Manual only $15 

VISA and MASTER CARD Welcome. 

Apple II Softcard • TRS-80 II and I 
SuperBrain • Heath H8/H89 • Altos 
NorthStar • Vector • MP/M • IBM 



1955 Pauline Blvd., Suite 200 

Ann Arbor, Michigan 48103 

(313) 996-1299 



CP M and MP M are regitfcrul trademarks of Digital Research, lite Apple II is a registered trademark of Apple 
Computer. Inc Softcard is a trademark of Microsoft TKS-80 is a trademark of Tandy Corjxjralion. 



Comp 



PRODUCTS, INC. 



Circle 450 on inquiry card. 



Here's just a taste 
of our great prices. 

To really least your eyes, send for our new catalog. 



Great prices are only 
one feature of our new 
catalog. More important- 
ly, we think you'll find it 
to be a well-written, 
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tool. 

When you receive our 
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our committment to 
help you keep it up to 
date. 

Unlike most catalogs 
that are obsolete the 
moment they're printed, 
ours is designed to ac- 
commodate all the 
rapid-fire changes in 
micro-computer hard- 
ware and software. Its 
loose-leaf-binder format 
makes it a snap to add 
the new pages we'll 
send out on a regular 
basis. 

Our new catalog was 
developed on exactly 
the same principles as 
our business — to offer 
you the lowest possible 
prices combined with 
the highest quality of 
service. 

16K RAM KITS... 13.95 

Sel ol 8 NEC 4116 200 ns. Guaranteed one lull 
year 

DISKETTES 

ALPHA DISKS 21.95 

Single sided, certified Double Density 40 Tracks, 
with Hub-ring. Box ol 10. Guaranteed one lull 
year. 



VERBATIM DATALIFE 

MD 525-01. 10, 16 26 50 

MD 55001 10. 16 44 50 

MD 557-01. 10 16 54 95 

MD 577-01 10. 1G 34 80 

FD 32 or 34-9000 3G 00 

FD 32 Or 34-R000 44 95 

FD 34-4001 48 60 

DISKETTE STORAGE 

5 v plastic library case 2 50 

8 plastic Library case 3 50 

PLASTIC STORAGE BINDER w/ Inserts 9 95 

PROTECTOR 5 V (50 Disk Capacity) 23 95 

PROTECTOR 8" (50 Disk Capacity) 29 95 

DISK BANK 5V 5 95 

DISK BANK 8' 6 95 



BRIDGE 
KAB00M 



21 95 

21 95 



HEWLETT PACKARD 

HP CALCULATORS 

HP- 1 1C LCD SCIENTIFIC 115.95 

HP-12C LCD BUSINESS 128.95 

HP-37E BUSINESS 64 95 

HP-32E SCIENTIFIC w/ STATS. 46.95 

HP-33C Programmable Scienlitic 76 95 

HP-41C Advanced Programmable 211 95 

HP-41CV Advanced Prng 2K mem 274 95 

HP-41 PERIPHERALS 

HP-82106A MEMORY MODULE 27.95 

HP-82170A Quad Memory Module 89 00 

HP-82143A PRINTER/PLOTTER 324 95 

HP-82160A IL INTERFACE 119 00 

HP-82161A DIGITAL CASSETTE 419.00 

HPMATHPAC 29 00 



NEC PERSONAL 




HP STATISTICS PAC 


29.00 


COMPUTERS 




HP REAL ESTATE PAC 
HP SURVEYING PAC 


39 00 
. . 29.00 


PC-8001A CPU 


899 00 


HP STRUCTURAL ANALYSIS PAC 


39.00 


PC-8012A I/O 

PC 8033A DISK I/O 


559 00 
125 00 


HP COMPUTERS 




PC-8031ADUAL DISK 


899 00 


HP-85A PERSONAL COMPUTER 


.21 95 






HP SINGLE 5V< "DISK DRIVE 


12.95 






HP DUAL DISK DRIVE 


19 95 


ALTOS COMPUTER 


HP-85A16K MEMORY MODULE 


239.00 


SYSTEMS 




HP-7225B GRAPHICS PLOTTER . 
HP PLOTER MODULE 


.21.95 
..605.00 


Call Alpha Byte tor our low Altos prices 




HP HP-IB INTERFACE 


329.00 






HPST0 APPLICATIONS PAC. .. . 


. 83.00 




HP GENERAL STATISTICS PAC 


83.00 


ATARI COMPUTERS 


HP GRAPHIC PRESENTATIONS 


159.00 


ATARI 800 


699 00 


HP VISICALL PLUS 


159 00 


ATARI 400 (16K) 


339 00 


HP ROM DRAWER 


39 00 


ATARI 810 DISK DRIVE 


449 00 


HP PRINTER/PLOTTER ROM . . 


116.00 


ATARI 850 INTERFACE 


449.00 


HP MASS STORAGE ROM 


11600 


ATARI 410 PROGRAM RECORDER 


79 00 


HPRS-232 INTERFACE 


329 00 


EPSON CABLE 


3500 


PRINTERS 




MEMORY MODULE (16K) 


89 95 






JOYSTICK CONTROLLERS 


10 00 


ANA0EX DP 9500 


1295 00 


PADDLE CONTROLLERS 


19 95 


ANADEX DP 9501 


1295.00 


STAR RAIDERS 


35 00 


C-IT0H 25 CPS PARALLEL 


1440 00 


MISSILE COMMAND 


35 00 


C-IT0H 25 OPS SERIAL 


1495 00 


ASTEROIDS 


35 00 


C-IT0H 45 CPS PARALLEL 


1770.00 


INTEC PERIPHERALS 




C-IT0H 40CPSSERIAL . 

C-IT0H PR0WRITER PARALLEL 


1870 00 
549.00 


RAM MODULES 




C-IT0H PR0WRITER SERIAL 


. 695.00 


48K FOR ATARI 400 


279 00 
135.00 


C-IT0H COMET I 


289.00 


32K FOR ATARI 800 


EPSON MX-80 


.SCALL 


ACTIVISION ATARI 




EPSON MX-80 F/T 
EPSON MX-100 GRAPHIC 


SCALL 
. .SCALL 


CARTRIDGES 




EPSON GRAFTRAX 


90.00 


LAZAR BLAST 


21.95 


IDS-445G PAPER TIGER 


.779.00 


SKIING . . . 


21.95 


IDS-460G PAPER TIGER . . 


94500 


DRAGSTER 


21.95 


IDS-560G PAPER TIGER 


.1195.00 


BOXING . . . 


21 95 


NECSPINWRITER3510S.R0 . 


2095.00 


CHECKERS 


21.95 


NECSPINWRITER3530P.ro.. 


2095.00 



NECSPINWRITER7710S.R0 264500 

NEC SPINWRITER 7730 P RO 2545.00 

NEC SPINWRITER 7700 DSELLUM 2795.00 

NEC SPINWRITER 3500 SELLUM 2295.00 

0KIDATA MICR0LINE 80 389.00 

DKIDATA MICR0LINE82A 549.00 

0KIDATAMICR0LINE83A 799.00 

OKIDATA MICROLINE 84 . ..1199.00 

0UME9/45 2149 00 

MALIBU 200 DUAL MODE 2695.00 

CORVUS 

FOR S-100, APPLE OR TRS-80 
MOD I, III 

Controller. Case/P S., Operating System. A & T. 

5 MEGABYTES 3245.00 

10 MEGABYTES 4645.00 

20 MEGABYTES . 5545.00 

MIRROR BACK-UP 725 00 

APPLE HARDWARE 

VERSA WRITER DIGITIZER 259.00 

ABT APPLE KEYPAD 119.00 

MICROSOFT Z-80 SOFTCARD 299.00 

MICROSOFT RAMCARD 159.00 

VIDEX 80 x 24 VIDEO CARD 299.00 

VIDEX KEYBOARD ENHANCER II .129.00 

VIDEX ENHANCER REV 0-6 99.00 

VIDEX SOFT SWITCH 29 00 

M & R SUPERTERM 80 x 24 VIDEO BD. . .315.00 
SSM AID BOARD (INTERFACE) A &T. .165.00 

SSM AID BOARD (INTERFACE) KIT 135.00 

APPLE FAN 44.95 

T/G JOYSTICK 54.95 

T/G PADDLE 34.95 

VERSA E-Z PORT 21.95 

MICRO SCI A40 W/CONTROLLER 479.00 

MICRO SCI A40 W/0 CONTROLLER .409.00 
MICRO SCI A70 W/C0NTR0LLER 629.00 

MICRO SCI A70 W/0 CONTROLLER . .549.00 

THE MILL-PASCAL SPEED UP 329.00 

PROMETHEUS VERSACARD . . . 229.00 

SUPERCLOCK II . .129.00 

LAZAR LOWERCASE + . . .59.00 

MIGROBUFFER II 16K 259.00 

MICR0BUFFER II 32K 299.00 

WIZARD 80 COL VIDEO 279.00 



MONITORS 

NEC 12" GREEN MONITOR 199.00 

NEC 13" COLOR MONITOR 399.00 

SANYO 12" M0NIT0R(B&W) 249.00 

SANYO 12" MONITOR (GREEN) 269.00 

SANYO 13" COLOR MONITOR. . . . 469.00 
ZENITH 13" HI RES GREEN MDN. . .139.00 

AMDEK COLOR I 389.00 

AMDEK RGB COLOR 859.00 

AMOEK RGB INTERFACE 169.00 



38 BYTE April 1982 



Circle 17 on inquiry card. 



MOUNTAIN 




100-3 SINGLE HEAD 80 TRK 


299 00 






100-4 DUAL HEAD 80 TRK 


429.00 


HARDWARE 












TANDON THINLINE 8 INC 


CPS MULTIFUNCTION BOARD 
SUPERTALKER SD200 


199.00 
259,00 


848-1 SINGLE SIDE 


459 00 


ROMPLUS W/ KEYBOARD FILTER 


179 00 


848-2 DUAL SIDE 


549 00 


ROMPLUS W/O KEYBOARD FILTER 


13000 






KEYBOARD FILTER ROM 


49 00 


MICRO PRO 




COPYROM 


49 00 






MUSIC SYSTEM 


36900 


APPLE CP/M" 




ROMWRITER 


149 00 


WORDSTAR* 


249.00 


APPLE CLOCK 


252,00 


SUPERSORT* 


145 00 


A/D + D/A 


299 00 


MAILMERGE* 


90.00 


EXPANSION CHASSIS 


625 00 


DATASTAR* 


215 00 






SPELLSTAR* 


169 00 


CALIF. COMPUTER 


CALCSTAft* 


169 00 


SYSTEMS 




CP/M 8 




S-100 BOARDS 




WOROSTAR 
SUPERSORT 


310.00 
195.00 


2200A MAINFRAME 


459.00 


MAILMERGE 


110.00 


2065C64K DYNAMIC RAM 


53900 


DATASTAR 


245.00 


2422 FLOPPY DISK CONT. &CP/M" 


35900 


SPELLSTAR 


195,00 


2710 FOUR SERIAL I/O 


27900 


CALCSTAR 


239.00 


2718 TWO SERIAL/TWO PARALLEL l/C 


) 269.00 






2720 FOUR PARALLEL I/O 
2810 Z-80 CPU 


199 00 
259,00 


MICROSOFT 




APPLE BOARDS 




APPLE 




7710A ASYNCHRONOUS S INTERFACE 149 00 


FORTRAN* . 


165,00 


7712A SYNCHRONOUS S INTERFACE 


159.00 


BASIC COMPILER* 
COBOL* . . 


315.00 


7424A CALENDAR CLOCK 


99.00 


595.00 


7728A CENTRONICS INTERFACE 


105,00 


Z-80 SOFTCARD . 


299.00 






RAMCARO 


159.00 


VISTA COMPUTER CO. 


TYPING TUTOR 

OLYMPIC DECATHLON 


17.95 
24,95 


APPLE VISION 80-80 COL CARD. 


329.00 


TASC APPLESOFT COMPILER 


159.00 


APPLE 8" DISK DRIVE CONTROLLER 


549.00 


CP/M" 








BASIC 80 


299.00 


MODEMS 




BASIC COMPILER. 


319.00 






FORTRAN 80 


369 00 


NOVATION CAT ACOUSTIC MODEM 


1*15.00 


COBOL 80 
MACRO 80 
mu MATH/mu SIMP 
mu LISP/itiu STAR 


595.00 
189 00 
219 00 
175,00 


NOVATION D-CAT DIRECT CONNECT 


165.00 


NOVATION AUTO-CAT AUTO ANS 

NOVATION APPLE-CAT 

UOS 103 LP DIRECT CONNECT 


2J9.00 

349.00 
175.00 


UOS 103 JLP AUTO ANS 


.209.00 






HAYES MICROMOOEM II (APPLE). 


299 00 


APPLE SOFTWARE 


HAYES 100 MODEM (S-100) 
HAYES SMART MODEM (RS-232) . 
HAYES CHRONOGRAPH 
LEXICON LX-11 MODEM 
RACAL VADIC 1200 BAUD/212A 


32500 
. 249.00 

225.00 
109.00 
795.00 


MAGIC WINDOW 
MAGIC SPELL 

BASIC MAILER .... 
APPLE PIE 
DB MASTER 


79.00 
59.00 
.,59,00 
99.00 
179.00 






PFS: PERSONAL FILING SYSTEM 


. 79.00 


TERMINALS 




PFS: REPORT 


,79.00 


TELEVIDE0 910 , . 
TELEVIOEO 912C. 
TELEVIOEO 920C 
TELEVIOEO 950C . 
ZENITH Z-19 


. 639.00 
745.00 
830,00 
995.00 
799.00 


Z-TERM* 

Z-TERM PRO* 

ASCII EXPRESS. 

HAYDEN APPLESOFT COMPILER 

EASY WRITER-PRO 

EASY MAILER-PRO 


,89,95 
.129.95 
.63,95 
149.00 
199.00 
..79.00 






EXPEDITER II APPLESOFT COMPILER. 


.73,95 


TRS-80 MOD 1 




A-STATCOMP. STATISTICS PKG 


,129.00 


HARDWARE 




SUPER TEXT II 

FINANCIAL PARTNER. 


,129.00 
.199.00 


PERCOM DATA SEPARATOR 


27 00 


LISA 2.5 


..59.95 


PERCOM DOUBLER II... 


159.00 


SUPERSCRIBE II 


. 99.95 


TANDON 80 TRACK DISK DRIVE 
TANDON 40 TRACK DISK DRIVE 


429.00 
.289.00 
159 00 


CONTINENTAL SOFTW 

G/L . . 


ARE 


LNW DOUBLER W/ DOSPLUS 3.4D. . 


.199.00 


MOO III DRIVE KIT 


649.00 


A/R 


.199.00 






A/P . . 


.199.00 


MORROW DESIGN 


s 

s 


PAYROLL 

PROPERTY MGMT. 


199.00 
.399.00 


FLOPPY DISK SYSTEM: 


THE HOME ACCOUNTANT. 


.59.95 


Controller. P.S.. Microsoft Basic. 


CP/M" 


PERSONAL SOFTWARE 


A & T. 


.869.00 
1499.00 
.1099.00 
.1999,00 


DESKTOP PLAN II 


.199.00 


DISCUS 2D (Single Drive - 500K) . 


ViSlPLOT 


. 179.00 


DISCUS 2D (Dual Drive- 1 MEG). .. . 


VISITREND/VISIPLOT 


.239.00 


DISCUS 2 + 2 (Single Drive - 1 MEG) 


VISIOEX 


. 199.00 


DISCUS 2 + 2 (Dual Orive - 2 MEG) 


ViSJTERM 


..79.00 


HARD DISK SYSTEMS 


CP/M" 


VISICALC 

VtSIFILES 


199.00 
. 209.00 


Controller, P.S.. Microsoft Basic. 






A& T. 

DISCUS M10 (10 Megabytes) 


3099.00 


CP/M® SOFTWARE 


DISCUS M26 (26 Megabytes) . . 


.3749.00 


THE WORD-SPELL CHECK 


.75.00 






d BASE II r 


599.00 


ISOLATORS 




SUPER CALC 


.229.00 










SPELLGUARO 


.239,00 


ISO 1 3-SOCKET 


.5395 


P&TCP/M* MOD II TRS-80 


..175.00 


ISO-2 6-SOCKET 


. 53,95 


COMMX TERMINAL PROG 


...82.50 






C BASIC 2 


.115.00 


BARE DRIVES 




PASCAL Z 


.349.00 






PASCAL MT+ 


439.00 


TANDON 5 1 /4 INCH 


PASCAL/M.. . 


. 205.00 


100-1 SINGLE HEAD40TRK 


.,219.00 


SYSTEMS PLUS - 




100-2 DUAL HEAD 40 TRK 


.299,00 


G/L, A/R. A/P. P/R 


1799.00 



CONDOR I 579.00 

CONDOR II 849.00 

DIGITAL RESEARCH 

MAC 89.00 

SID 6900 

ZSIO 97.00 

PL/ 1-80 .439.00 

SUPERSOFT 

DIAGNOSTIC I .... 69.00 

DIAGNOSTIC II 89.00 

X' COMPILER 179,00 

UTILITIES I 59.00 

UTILITIES II 59.00 

RATFOR 89.00 

FORTRAN 239.00 

TRS-80 GAMES 

TEMPLE OF APSHAI 34.95 

HELLFIRE WARRIOR 34 95 

STAR WARRIOR 34.95 

RESCUE AT RIGEL 24.95 

CRUSH. CRUMBLE ANDCHOMP 24.95 

INVADERS FROM SPACE 17.95 

PINBALL . , 17,95 

STAR TREK 35 17 95 

MISSILE ATTACK 18 95 

STAR FIGHTER 24 95 

TRS-80 SOFTWARE 

NEWDOS/80 2.0 MOD I. II 13900 

LAZY WRITER MOD I, II 165.00 

PROSOFT NEWSCRIPT MOD I. Hi 99 00 

SPECIALDELIVERYMOOI.III 119.00 

X-TRA SPECIAL DELIVERY MODI. Ill 199,00 

TRACKCESSMOOI 24.95 

OMNITERM SMART TERM, MOD I. Ill 89 95 

MICROSOFT BASICCOMP FOR MOD I 165.00 

LDOS 5 1 MOO I. II 15900 

APPLE GAMES 

PERSONAL SOFTWARE 

CHECKER KING . . 21.95 

GAMMON GAMBLER 21.95 

BRIDGE PARTNER 21.95 
MONTY PLAYS MONOPOLY .. .29.95 

ZORKI 32.95 

ZORK II 32.95 

MONTY PLAYS SCRABBLE 34.95 

BRODERBUND 

GALAXY WARS. 20.95 

ALIEN RAIN (AKAGALAXIAN) 20.95 

ALIEN TYPHOON 20.95 

APPLE PANIC 24.95 

MIDNIGHT MAGIC ,29.95 

SPACE QUARKS 24.95 

AUTOMATED SIMULATIONS 

INVASION ORION 20.95 

STAR WARRIOR 32.95 

TUES. MORNING QUARTERBACK 25.95 

CRUSH. CRUMBLE AND CHOMP 24.95 

THE DRAGON'S EYE 20.95 

MUSE SOFTWARE 

ROBOT WARS 32.95 

THREE MILE ISLAND 32.95 

A.B.M 20.95 

GLOBAL WAR 20.95 

CASTLE WOLFENSTEIN 24.95 

ON-LINE SYSTEMS 

WIZARD AND PRINCES. 29.95 

MISSILE DEFENSE 25.95 

SABOTAGE 20.95 



SOFT PORN ADVENTURE 24.95 

THRESHOLD 31.95 

JAW BREAKER 24.95 

CROSSFIRE 16.45 

TIME ZONE 69.95 

H/R FOOTBALL 32.95 

H/R CRIBBAGE 20.95 

PEGASUS II 25.95 

SIRIUS SOFTWARE 

SPACE EGGS 24.95 

GORGON 32.95 

SNEAKERS 24.95 

EPOCK . .29.95 

BEER RUN 24.95 

HADRON 29.95 

PULSAR II . . 24.95 

EPOCK 29,95 

EDU-WARE 

PERCEPTION PKG. 19.95 

COMPU-READ 24.95 

STORY TELLER , 18.95 

GOMPU-M'ATH: ARITHMETIC 39.95 

COMPU-MAT.H. FRACTIONS . . 34,95 

COMPUMATH: DECIMALS 34.95 

COMPU-SPELL (REO. DATA DISK) 24.95 

COMPU SPELL DATA DISKS 1-4, ea 1 7.95 

MORE GREAT APPLE 
GAMES 

COMPUTER QUARTERBACK 32.95 

TORPEDO FIRE . 49.95 

THE SHATTERED ALLIANCE 49.95 

POOL 1 5 29.95 

ULTIMA 33.95 

RASTER BLASTER 24,95 

FLIGHT SIMULATOR 27.95 

INTERNATIONAL GRAND PRIX 25.95 

SARGQNII 28.95 

SHUFFLE BOARD 29.95 

FIREBIRO 24.95 

SNACK ATTACK 24.95 

THIEF 24.95 

ROACH HOTEL 29.95 

JABBERTALKY 24.95 

THE WARP FACTOR 32.95 

COSMO MISSION 24.95 

SUPPLIES 

AVERY TABULABLES 

1.000 3V? x 15/16 8.49 

3.000 3'/z x 15/16 14.95 

5.000 Vh x 15/16 19.95 

FAN FOLD PAPER 

(Prices F.O.B. S.P.) 

9V? x 11 1810 WHITE 3.000 ct 29.00 

14 7/8 x 11 181b WHITE 3.000cl 39.00 




IPUTER 
PRODUCTS 

To order, or for information, call: 

(213)706-0333 

To use our 24-hour modem order line, call: (21 3) 883-8976. 

We guarantee everything for 30 days. If anything is wrong, return the item 
and we'll make it right. And, of course, we'll pay the shipping charges. 

We accept Visa and Master Card on all orders; COD up to $300.00. 

Add $2.00 for standard UPS shipping and handling on orders under 50 lbs, 
delivered in continental U.S. Call for shipping charges over 50 lbs. Foreign, 
FPO and APO orders, add 15% for shipping. Californians add 6% sales tax. 

Prices quoted are for stock on hand and subject to change without notice. 

31245 LA BAYA DRIVE, WESTLAKE VILLAGE, CALIFORNIA 91362 



Circle 17 on inquiry card. 



CP/M is a reg. trademark of Digital Research. 



•Requires Z-80 Soltcard. 



BYTE April 1982 39 



Ciarcia's Circuit Cellar 



Use Infrared Communication 
for Remote Control 

The Texas Instruments SN76832AN Infrared Remote-Control 

Receiver simplifies the tough job of receiving 

modulated infrared light. 



Steve Ciarcia 

POB 582 

Glastonbury, CT 06033 



Two dozen images of Howard 
Cosell danced before my eyes. Sud- 
denly there were two dozen images of 
acid indigestion, and then, just as 
suddenly, Howard Cosell was back. 

Undaunted, I stood my ground, 
which happened to be in the televi- 
sion department of a large store a few 
miles from home. I was wielding a 
small box covered with push-button 
switches, trying out a display of 



About the Author 

Fifteen years ago, Steve Ciarcia (pronounced 
"see-AR-see-uh") gave up a promising career as 
a security guard for the Famous Writers' 
School to become an electrical engineer and 
computer consultant. He has experience in 
nuclear instrumentation, process control, 
digital design, product development , and 
marketing. In addition to writing for BYTE 
magazine, he has published several books, in- 
cluding Build Your Own Z80 Computer (BYTE 
Books, 1981). 

When he's not working in his Circuit Cellar, 
he enjoys cooking such foods as Eggplant 
Siciliana and Shrimp Proven^ale and driving 
his DeTamaso Pantera sports car. 



remote-controlled TV sets. 

There has been a silent revolution 
going on in the TV remote-control 
business. Silent indeed. No longer do 

Detecting an 

information-bearing 

infrared beam in an 

infrared-saturated 

environment is a 

signal-to-noise 

horror show. 



the control boxes emit ultrasonic im- 
pulses that drive all the dogs in the 
household into hysterics. Today's 
remote-controlled TV sets receive 
viewers' instructions on beams of in- 
frared light. 

The silent revolution has also made 
controlling the sets easier. Ultrasonic 
remote-control units, because of their 
complexity and cost, usually have 
had only two or three control chan- 



nels, making channel changing a 
tedious, repetitive task and limiting 
the set functions that could be 
remotely commanded. 

Infrared-light units are not only 
practical; they have become much 
more sophisticated, often making 
available thirty or more control chan- 
nels for less than the cost of a pair of 
ultrasonic transducers. 

To supply the demand for support 
circuitry to build remote-control 
systems, several semiconductor man- 
ufacturers (such as General Instru- 
ment, Hitachi, Signetics, and Texas 
Instruments) are producing integrated 
circuits that encode and decode the 
command information used in these 
TV remote controls. Most encoder 
chips are designed to accept a key- 
board input and directly modulate an 
infrared light source. At the receiving 
end, the encoded data stream is 
decoded by a decoder chip and a few 
discrete components. 

I decided to buy a pair of infrared 
encoder/decoder chips and build a 



40 April 1982 © BYTE Publications Inc 



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RELATIVE SPECTRAL CHARACTERISTICS 



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Figure 1: Relative spectral characteristics of infrared light-emitting diodes and photo- 
diodes. 



quick and dirty remote-control unit. 
It was going to be so easy. 

Not so fast! There was a missing 
link: detecting the beam of infrared 
light so it could be decoded. 

To Find a Missing Link 

Was I going to let a little thing like 
a beam of light stop me? Of course 
not. I started investigating how to 
sense a beam of infrared light. 

Once again I found myself working 
on a topic about which I could find 
very little published information of 
use in practical experimentation. I 
suspect there have been few magazine 
articles dealing with infrared-light 
communication because of the diffi- 
culty in detecting an information- 
bearing beam of infrared light in an 
infrared-saturated environment. It's a 
signal-to-noise horror show I The sen- 
sitivities and dynamic ranges required 
are beyond simple amplifier-design 
techniques. My goal of building an 
inexpensive remote-control scheme 
using TV-set encoder/decoder chips 
therefore had to wait until I first 
designed a reliable infrared com- 
munication receiver. 

This article contains both a discus- 
sion of optical communication and a 
construction project of a useful in- 
frared-light transmitter/receiver in- 
terface for use with a personal com- 
puter. Along the way I attempt to 
answer some basic questions includ- 
ing the following: In what kind of ap- 
plications can light transmission be 



useful? Why use infrared rather than 
visible light? What is the best choice 
of optoelectronic components for 
each application? 

Why Use Light? 

Light is used in communication for 
two major reasons: the medium's 
immunity to certain forms of 
interference and the relative ease of 
providing security for the communi- 
cations link. Electrically noisy motors 
and other equipment generate electro- 
magnetic interference (EMI) that can 
play havoc with radio-wave trans- 
missions, and ambient noise can 
disrupt ultrasonic communication. 
These problems do not bother light 
beams, and a protected line-of-sight 
beam path or waveguide provides fair 
security against unauthorized inter- 
ception. 

Light can also be used in providing 
physical security for premises; a 
prowler might step over a tripwire, 
but he wouldn't know to avoid an in- 
visible shaft of infrared light aimed at 
a detector in an alarm system. 

What Is Infrared Light? 

The segment of the electromagnetic 
spectrum that we perceive optically 
as visible light is narrow. On both 
sides of this band of visible light are 
regions of radiation that we can't see 
but which otherwise exhibit similar 
optical properties. Radiation of 
wavelengths shorter than we can see 
is called ultraviolet (UV) light, while 



wavelengths longer than we can see 
form infrared (IR) light. Any warm 
object radiates some amount of in- 
frared radiation. 

(Some may quibble with my use of 
the term "light" to discuss radiation 
that cannot be seen. I feel that any 
radiation that can be manipulated op- 
tically [by lenses and the like] should 
be called light, and that's how I am 
using the term in this article.) 

The spectral graph of figure 1 
shows that the visible band has wave- 
lengths between about 400 and 700 
nm (nanometers). Within the range of 
400 to 700 nm, the different frequen- 
cies are perceived as different colors. 
For example, a light beam of 550-nm 
wavelength is perceived as green. 
What we perceive as white light con- 
tains all the visible frequencies. 

Transmitting information on a 
beam of light is done much the same 
way as on a radio wave. The light 
must be amplitude-modulated at 
some carrier frequency, say 40 kHz. 
This allows the receiver to differen- 
tiate between the light coming from 
the transmitter and unmodulated am- 
bient light. The data to be transmitted 
can be modulated onto the carrier in a 
number of ways, including amplitude 
and frequency modulation, pulse- 
width modulation (PWM), and pulse- 
code modulation (PCM). 

For my application of a simple op- 
tical remote-control system, the less 
complicated PCM technique seemed 
best. This merely consists of turning 
the 40-kHz-modulated light on and 
off. At the receiving end, the presence 
of light is interpreted as a logic 1 and 
the absence of light as a logic 0. 

Why use so high a carrier frequen- 
cy? We have to use a frequency high 
enough that the communication is not 
susceptible to interference. The 
operating environment of our in- 
frared system may contain such 
sources of interference as fluorescent 
lights, which flash at 120 Hz, or 
television sets, whose screens emit 
light with interference patterns at 
over 15 kHz. For open-air optical 
communication, frequencies at or 
above 40 kHz are preferred. 

Any electrically excited light source 
can be amplitude modulated, but not 



April 1982 © BYTE Publications Inc 41 



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Figure 2: Cross section of the structure of a standard visible red light-emitting diode. 



Blue LEDs at Last 

Longtime readers of BYTE may 
recall Steve's article from several years 
ago on a self-refreshing LED graphics 
display (see reference 2). In it, he 
described how single-color graphic im- 
ages can be formed on display panels 
containing arrays of many red light- 
emitting diodes and suggested that 
multicolor images could be displayed 
on a panel that contained arrays of 
triads of different-color LEDs. But his 
suggestion was ahead of technology. 
At that time, no practical method was 
known for making an LED that could 
emit blue light. 

Now the blue-light barrier has been 
broken, and in a way eminently suit- 
able to flat-panel graphics displays. In 
October 1981, the Sanyo Electric Com- 
pany of Japan unveiled an LED lamp 
component that contains two separate 
LED chips, one of which emits blue 
light at a wavelength of 480 nano- 
meters (see reference 3). The blue- 
emitting chip is formed from two 
liquid-phase-epitaxial layers of silicon 
carbide grown on a silicon-carbide 
wafer. The other chip, made of gallium 
phosphide with four epitaxial layers, 
can emit both red light at 700 nano- 
meters and green light at 565 nano- 
meters. A single component that can 
produce all three additive primary col- 
ors makes possible a full-color, flat- 
panel LED graphics display. 

The voltage potential dropped by 
the blue LED chip is about 3.5 V, pro- 
ducing 2 mcd (millicandelas) of light, 
while the two-color chip drops 2 V for 
3 mcd of green light and 1.9 V for 3 
mcd of red light. Thus we see that real 
components reflect the theoretical 
predictions of greater efficiency at 
longer wavelengths. . . . RSS 



all of them at 40 kHz. Modulating a 
100-watt incandescent light bulb at 
such a high frequency is out of the 
question: the thermal time constant 
of the filament is much too long. The 
only light sources capable of switch- 
ing at such a frequency are elec- 
troluminescent devices, of which the 
light-emitting diode (LED) is the least 
expensive and most familiar. 

In a light-emitting diode, shown in 
figure 2 on page 42, light is generated 
when a forward-bias current is ap- 
plied. This causes electrons to be in- 
jected into the n-type (negative- 
doped, electron-rich) semiconductor 
material and holes (shortages of elec- 
trons) to be injected into the p-type 
(positive-doped, electron-poor) 
material. 

When the injected electrons and 
holes recombine with the majority 
carriers at the p/n junction, energy is 
released in the form of photons. The 
pattern of radiation emission can be 
controlled somewhat by reflective 
surfaces within the mounting struc- 
ture and by plastic lenses. Generally, 
a spherical dome lens with a narrow 
beam width is best for communica- 
tion. 

The color of the light emitted de- 
pends upon what semiconductor 
materials are used in the p/n junction 
and how they are doped (seeded with 
selected impurities): the amounts of 
energy released in the electron/hole 
recombinations of different materials 
vary, and the wavelength (and there- 
fore the color) of light varies in a 
direct relation to the amount of 
energy contained in its photons. 

Most of the semiconductor 
materials used in LEDs are com- 



pounds of gallium: gallium arsenide 
phosphide (GaAsP, which emits red, 
orange, or yellow light), gallium 
phosphide (GaP, green emitting), 
gallium aluminum arsenide (GaAlAs, 
red emitting), and gallium arsenide 
(GaAs, which emits infrared photons 
at about 900 to 1000 nm). The effi- 
ciency of an LED depends upon 
wavelength. The longer the wave- 
length, the higher the efficiency (see 
the text box "Blue LEDs at Last"). 

Operating at longer wavelengths, 
infrared LEDs are more efficient than 
visible-light red or green LEDs; IR 
LEDs are therefore preferred for line- 
of-sight beam breaking or communi- 
cation. For a given power input, an 
IR LED produces a brighter light than 
a green LED. Many IR LEDs have 
radiant-power outputs of more than 
10 mW (milliwatts)— for instance, the 
TIL39 component I have been experi- 
menting with has an 11-mW output at 
940 nm. 

Efficiency is important, because an 
LED is almost a point source of light. 
The illumination it casts on a surface 
is proportional to its brightness and 
inversely proportional to the square 
of the distance to the surface. If we 
want our open-air communication 
link to operate over distances as great 
as 10 meters, our LED light source 
must be very bright to produce an ac- 
ceptable signal-to-noise (S/N) ratio 
using an ordinary-sized receiving 
photosensor measuring perhaps 0.1 
cm 2 (square centimeter). 

Other incentives for using IR light 
are reduced sensitivity to ambient 
visible light, greater ability to pierce 
through fog or smoke, and better re- 
flection off most surfaces for a greater 
chance that the receiver will be able 
to see the light source. 

Choosing the Light Detector 

Choosing the proper light detector 
is as important as selecting the light 
emitter. Selectivity, response, and in- 
herent noise are important considera- 
tions. 

There are many materials which 
function as photoconductors. The 
simplest are bulk materials such as 
cadmium selenide (CdSe), lead sulfide 
(PbS), and cadmium sulfide (CdS). 



42 April 1982 © BYTE Publications Inc 



Generally these materials exhibit 
poor temperature stability and are 
sensitive over a very broad range of 
wavelengths. 

The familiar semiconductors ger- 
manium (Ge) and silicon (Si), on the 
other hand, are sensitive chiefly to 
the near-infrared (wavelengths close 
to the visible range) light radiated by 
IR LEDs. 

Two types of devices that use 
silicon and germanium are photo- 
diodes and phototransistors. Photo- 
transistors are constructed in much 
the same manner as commonplace 
planar-diffused transistors. The base 
area is usually made large to provide 
an area into which incident light can 
penetrate and generate electron/hole 
pairs. Phototransistors are subject to 
the variation in performance typical 
of all transistors. 

Many of the bad traits of photo- 
transistors are eliminated in PIN 
photodiodes. The term PIN is an 
acronym meaning that the compo- 
nents are made from three layers of 
different types of semiconductor 
material: p-type, "intrinsic, " and 
n-type. A PIN photodiode is one in 
which two heavily doped p and n 
regions are separated by a lightly 
doped region (which exhibits mostly 
properties intrinsic to the substance). 
Its large depletion region (interface 
region between the p-type and intrin- 
sic layers) provides the PIN photo- 
diode with much faster speed, lower 
noise, and greater efficiency at longer 
wavelengths. 

Photo 1 shows a TIL413 infrared- 
sensitive PIN photodiode (right) and 
a TIL39 infrared light-emitting diode 
(left). 

Ready-Made IR Detector 

Designing a reliable infrared-light 
detector/receiver is no simple task; it 
has been the major obstacle in design- 
ing any infrared communication sys- 
tem. The engineer must coax his" 
receiver into extracting the trans- 
mitted data from a dismaying amount 
of background noise, and he must 
take care that his design will with- 
stand the impairments to theoretical 
performance caused by deviations 
from ideal component values and 
manufacturing techniques. But there 




X/ 



X, 



I 



Photo 1: The TIL413 infrared-sensitive PIN photodiode (right) and the TIL39 in- 
frared light -emitting diode (left). 




Photo 2: Prototype of the infrared-light remote-control or communication re- 
ceiver of figure 4. 



is nothing conceptually complicated 
in the receiver, just a photodiode and 
a series of amplifiers and filters. 

I haven't presented an infrared 
communication system before now 
because I couldn't design one that I 
felt readers could successfully 
duplicate. But recently I discovered 
that an integrated circuit has been de- 



veloped to do all the hard work. 
Texas Instruments recognized the 
need and designed a chip which 
eliminates all the frustrations in 
building the IR receiver. 

The new component is the 
SN76832AN Infrared Remote-Con- 
trol Receiver. This chip replaces a 
combination of several integrated cir- 



April 1982 © BYTE Publications Inc 43 



TUNED INPUT 
STAGE 



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]LOCK FILTER 

] FIRST AMPLIFIER DECOUPLING 

] FIRST AMPLIFIER OUTPUT 

] FIRST AMPLIFIER INPUT 

] AMPLIFIER SUPPLY DECOUPLING 

] GROUND 



Figure 3: Block diagram of the internal structure of the Texas Instruments SW 6832 AN 
Infrared Remote-Control Receiver. 



cuits and discrete components. It con- 
nects directly to a PIN photodiode 
and is designed to receive and detect 
digitally encoded information modu- 
lated on a carrier (typically 40 kHz). 
It has an open-collector gated output 
suitable for direct operation with a 
microprocessor. For the benefit of 
readers of BYTE, the Micromint will 
be distributing a kit that includes the 
SN76832AN (see page 49). 

A block diagram of the SN76832AN 
receiver chip is shown in figure 3 . In- 
side the receiver chip, the signal from 



the photodiode is connected to an 
amplifier with an input impedance of 
220 kilohms and a typical gain of 1.6 
million volts/amp at 40 kHz. The 
output of this first amplifier stage is 
fed to a differential amplifier coupled 
to the demodulator section. 

The receiver chip demodulates the 
signal by comparing its amplitude 
and phase with that of reference 
signals produced by a voltage-con- 
trolled oscillator (VCO) and a fre- 
quency divider. The bandwidth and 
capture frequency are controlled by 



external passive components. The de- 
modulated output signal is filtered 
and gated by the output-enable con- 
trol signal. (A high level on the 
output-enable line causes the demod- 
ulated signal to appear on the output 
line. If the demodulated signal is to be 
constantly present, the output-enable 
line should be tied high.) 

Figure 4 on page 45 is a schematic 
diagram of the completed circuit for a 
very sensitive IR receiver which oper- 
ates at a carrier frequency of 40 kHz. 
A prototype is shown in photo 2. 

In the receiver circuit of figure 4, 
potentiometer Rl sets the frequency 
of the VCO, which is twice that of the 
capture frequency (the center fre- 
quency of the incoming modulated 
carrier signal). With the external 
oscillator-control components shown, 
this circuit can detect carrier frequen- 
cies from 20 kHz to 70 kHz. The rest 
of the components, however, are op- 
timized for 40-kHz operation. The 
photodiode I suggest is a type TIL413, 
because it has a spherical lens that 
allows it to "see" over a wider angle, 



44 April 1982 © BYTE Publications Inc 



EXTERNAL 

OUTPUT 

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Figure 4: Schematic diagram of a remote-control or communication circuit based on the SN76832AN. This circuit is set up for use at 
40 kHz, although the voltage-controlled oscillator can be adjusted from 20 kHz to 70 kHz. Any voltage from + 5 V to + 18 V may 
power the circuit. 



thus enhancing the effective sensitivi- 
ty. In a pinch other photodiodes such 
as the TIL100 may be used. 

The data output is permanently en- 
abled in my design unless the 
external-output-enable line is brought 
to ground potential by external 
means. The output signal is buffered 



and level-shifted through transistors 
Ql and Q2 to provide a TTL- (tran- 
sistor-transistor logic) compatible 
output. The circuit runs at any volt- 
age between + 8 V (volts) and +18 
V. I run it at +12 V. 

When the circuit "sees" a 40-kHz- 
modulated infrared light beam, the 



output goes to a normally high state, 
and the indicator light (LEDl) comes 
on. The output then changes state in 
accordance with the demodulated 
data, exactly duplicating the sequence 
of the logic levels of the input signal 
that was fed into the infrared 
transmitter. 




Photo 3: Prototype of the infrared transmitter assembly, 
internal view. 













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transmitter is to the right. The TIL413 photodiode is the 
small projection to the right of center of the receiver's 
front panel; the smalt projection on the left is a visible red 
LED that lights when the infrared carrier is detected. 



April 1982 © BYTE Publications Inc 45 



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Figure 5: Schematic diagram of a handheld infrared remote-control transmitter. Four pushbutton switches actuate a NAND gate 
wired as an oscillator; different frequencies may be selected for testing or in communicating simple command functions. Two high- 
power infrared and one visible indicator light-emitting diodes are modulated at a carrier frequency of 40 kHz; control signals are sent 
as a simple on/off modulation of the 40-kHz-modulated light beam. 




Figure 6: A simple circuit that provides 
only a 40-kHz carrier modulation for an 
infrared beam. This may be used for sim- 
ple beam-breaking intrusion-detection 
schemes. 



A Matching Transmitter 

After building and testing the 
receiver section, I argued with myself 
about an appropriate transmitter. 
The "hardware" side of me wanted to 
follow up on the inspiration that got 
me started on the project by using one 
of those complex encoder/decoder 
chip sets previously mentioned. The 
encoder chip would be built into the 
transmitter, and the decoder would 
be connected to the infrared-receiver 
circuit, providing parallel decoded 
outputs. 

The "software" side of me (I do 
have one I) argued that anything these 
chips could do in encoding and de- 
coding could be done by any fairly 
competent programmer in a few lines 
of code. The real challenge of the pro- 
ject was creating the infrared-light 



communication link, not encoding 
and decoding the signal. 

In the end, I decided that my inspir- 
ing vision was not worth the trouble, 
and I designed a relatively simple 
transmitter essentially consisting of a 
gated 40-kHz oscillator driving a pair 
of high-power infrared LEDs. As you 
can see in the schematic diagram of 
figure 5, jumper connections on the 
oscillator can be changed to allow 
modulation from an external signal 
source or to allow the communication 
link to be tested by your pushing one 
of the four pushbutton switches con- 
nected to the CD4011 NAND-gate 
component (ICl). The prototype 
transmitter circuitry is shown in 
photo 3 on page 45. The assembled 
transmitter and receiver are shown in 
photo 4 on the same page. 



46 April 1982 © BYTE Publications Inc 



In the transmitter circuit, ICl is 
configured as a low-frequency 
oscillator. The four switches control 
the frequency of the oscillator. With 
the "1" button pressed, an 8-Hz, 
50-percent-duty-cycle waveform is 
directed to the IR LEDs. Pressing "2" 
produces a 16-Hz waveform, pressing 
"4" produces a 32-Hz waveform, and 
pressing "8" produces a 64-Hz wave- 
form (the exact frequencies may vary 
somewhat). By pressing two or more 
of the buttons together, a total of 16 
distinct frequencies can be created. 



System Testing and Use 

To test the transmitter and 
receiver, aim the transmitter's IR 
LEDs in the general direction of the 
receiver unit and press the buttons. 
The output signal from the receiver 
should be the frequency correspond- 
ing to the switch operated on the 
transmitter. 

The single-bit output of the 
receiver can be connected to any con- 
venient input line on your computer 
(such as a game-paddle input), and a 
simple program can be written to 
count and determine the frequency of 
the input signal. While much higher 
frequencies can be transmitted by this 
system, I chose these low, pulsed fre- 
quencies so that even a BASIC pro- 
gram could count the frequency. 
Nevertheless, if the frequencies are 
still too fast, simply substitute a 
higher capacitance for Cl in the 
transmitter circuit of figure 5 on page 
46. 

The external modulation input of 
the transmitter is quite suitable for 
use in a wireless data link. Attach a 
serial output from your computer to 
the external data-input line, and con- 
nect the output of the receiver to 
another computer or to a remotely 
located printer. 

In fulfillment of my original plan, I 
decided to configure the transmitter 
in my infrared remote-control system 
as a hand-held actuator. 

If you simply want an infrared 
beam source for use as an intrusion 
detector in a security system, you 
don't have to build the entire data- 
transmission circuit; the simple 




Photo 5: The familiar BSR X-10 hand- 
held control unit. This was built to 
work using ultrasonic pulses, but it can 
be modified to use infrared light. The 
added infrared LED can be seen on top 
of the housing. 



CUSTOM BSR 
IC PIN 7 



Q 



40-kHz oscillator in figure 6 on page 
46 will work nicely. 

TV-Set Controllers, Too 

After building the IR receiver and 
transmitter circuits described, I 
discovered that signals from any of 
the commercial TV-set remote-con- • 
trol transmitters could be received 
just as easily as those from the 
transmitting device I had designed. 
Most set controls operate with car- 
riers in the 38-kHz to 41-kHz range. 
Of course, the data output that you 
get is a coded bit stream, generally 5 
to 12 bits repeating every half second, 
but this should be no obstacle. 

While I haven't analyzed the coded 
TV-set-control data, they should be 
susceptible to differentiation by the 
same methods that worked for my 
simple frequency input. Perhaps 
you'd have to use a machine-language 
program to catch the fast data (about 
25 milliseconds per word), but the 
results would be a professional- 
quality, very versatile remote inter- 
face to your computer. 

BSR Goes Infrared 

The remote-control transmitters 
for television sets are not the only 
means to an elegant remote-control 



CUSTOM BSR 3 

IC PIN 15[> — vw 



. 2N2222 



UJ)tIL39 

330^iF; 

;ioa 



A 



BLACK 

BATTERY 

LEAD 



Figure 7: Modification of the hand-held 
ultrasonic transmitter of the BSR X-10 
Home Control System that converts it to 
infrared-light operation. 

system for your computer. 

Perhaps you have on hand the 
hand-held transmitter from the BSR 
X-10 Home Control System. (Some of 
you may remember when I wrote 
about the BSR X-10; see reference 1.) 
This unit was made to work using 
ultrasonic sound, but it can be easily 
adapted for IR transmission to work 
with the receiver circuit in this article. 
Photo 5 shows the adapted BSR X-10 
transmitter. 

The modification is outlined in 
figure 7 and shown in photo 6 on 
page 48. Note that the ground con- 
nection should be the black lead 
directly connecting to the battery. 
The other two circuit connections are 
to pins 7 and 14 on the integrated cir- 
cuit as illustrated. The BSR transmit- 
ter already operates using a carrier 
frequency of 40 kHz. The modifica- 
tion is simply to add an emitter- 
follower IR LED driver to the output 
section. The existing ultrasonic 
transducer can be cut out or used con- 
currently with the optical transmitter. 

The message transmitted by the 
X-10 hand-held unit is approximately 
100 milliseconds (ms) long and is 
composed of 13 eight-millisecond seg- 
ments, each of which consists of a 
burst of 40-kHz signal. The reception 



April 1982 © BYTE Publications lnc 47 




Photo 6: Interior view of the modified BSR X-10 hand-held transmitter, modified according to figure 7. 



of the 40-kHz carrier will be marked 
by a high logic level coming out of the 
infrared receiver board for the dura- 
tion of the 40-kHz signal. The coded 
data is sent as a series of 1.2-ms and 
4-ms bursts, representing logic and 
1 respectively. The complete 13-bit 
message consists of a start bit (logic 
1), 5 data bits corresponding to the 
key being pressed, 5 bits representing 
the logical inversion of the first 5 data 
bits, and 2 stop bits (logic 1). The 
binary codes and the transmission se- 
quence are shown graphically in 
figure 8 on page 49. 

I'm sorry I was halfway through 
writing this article before I thought to 
use the BSR X-10 controller. After the 
idea struck home, I took a pizza 
break. Then I came back to the Cir- 
cuit Cellar, added the modification of 
figure 7, and verified correct data 



reception using an oscilloscope. I 
haven't actually written the code to 
interpret the BSR controller's signals 
yet. But considering the well-docu- 
mented transmission protocol used in 



The longer the wave- 
length of its light, the 
higher the efficiency of 
an LED. 



the BSR, it may be easier to use this 
unit rather than figure out the 
unknown coding of a TV remote- 
control unit. 

In Conclusion 

Building a reliable infrared receiver 
has been a goal of mine for a long 



time. Many of my first designs did 
eventually work, but they couldn't be 
easily duplicated. Since I believe that 
many other experimenters are equally 
interested in IR communication and 
have experienced similar frustrations, 
I have arranged with Micromint to 
make available a complete kit of the 
infrared-communication circuits 
shown in figures 4 and 5. Included 
with these kits is a complete data 
sheet on the SN76832AN should you 
care to configure it for another fre- 
quency range. 

If you try infrared communication 
and are successful, you might develop 
applications for it that have previous- 
ly been ignored. Certainly experi- 
menters like myself have been look- 
ing for better types of man/machine 
interaction than presently exist. Until 
computer speech recognition becomes 



48 April 1982 © BYTE Publications Inc 



^START OF MESSAGE 
(LOGIC 1) 



D8 



D2 



Dl 



■ COMPLETE MESSAGE ■ 



D8 



D4 



D2 



• START 



D8- 



-»| 8ms L — 



EACH DIVISION IS 8ms 



— »] 24ms 



h- 



D OR F 
LOGIC "1" 



40kH2 



4ms 



8 ms 



D OR F 
LOGIC "0" 



1.2 J*-— 
8ms 



Figure 8: Timing diagram and binary command-code table used by the BSR 
X-10 Home Control System. 



CHANNEL NUMBER 




BINARY 


CODE 




OR FUNCTION 


D8 


D4 D2 


Dl 


F 


1 





1 1 








2 


1 


1 1 








3 





1 








4 


1 


1 








5 













6 


1 










7 





1 







8 


1 


1 







9 





1 1 







10 


1 


1 1 







11 





1 







12 


1 


1 







13 














14 


1 











15 





1 








16 


1 


1 








ALL OFF 













ALL LIGHTS ON 








1 




ON 





1 







OFF 





1 


1 




DIM 





1 







BRIGHT 





1 


1 





practical, we shall have to be satisfied 
with pushing buttons to communicate 
with computers. But perhaps the in- 
frared transmitter and receiver in this 
article can make the connection a lit- 
tle more convenient. 

Next Month: 

It's been a long time since I wrote 
about time, time as measured by a 
computer's real-time clock. Next 
month, we'll look at plans for 
connecting a versatile clock to a per- 
sonal computer. ■ 



Editor's Note: Steve often refers to previous 
Circuit Cellar articles as reference material for 
each month's current article. Most of these past 
articles are available in reprint books 'from 
BYTE Books, 70 Main St., Peterborough, NH 
03458. Ciarcia's Circuit Cellar, Volume I 
covers articles that appeared in BYTE from 
September 1977 through November 197 8. Ciar- 
cia's Circuit Cellar, Volume II contains articles 
from December 1978 through June 1980. Ciar- 
cia's Circuit Cellar, Volume III contains the ar- 
ticles that were published from July 1980 
through December 1981. 



Parts Source 

The following is available from: 

The Micromint Inc. 

917 Midway 

Woodmere, NY 11598 

telephone (516) 374-6793 

(for technical data) 
(800) 645-3479 
(orders only) 

Infrared Transmitter/ Receiver 
Kit. $42 

Includes two printed-circuit 
boards (one for the transmitter and 
one for the receiver) and all com- 
ponents shown in figures 4 and 
5. Does not include the cases and 
power supplies shown in the pro- 
totype photos. Assembly manual 
and specification sheets provided. 

Please include $2 for delivery 
within the United States or $6 for 
foreign delivery. Residents of New 
York state please add 7% sales tax. 



References 

1. Ciarcia, Steve. "Computerize a Home," 
BYTE, January 1980, page 28. 

2. Ciarcia, Steve. "Self-Refreshing LED 
Graphics Display," BYTE, October 1979, 
page 58. Reprinted in Ciarcia's Circuit 
Cellar, Volume II. Peterborough, NH: 
BYTE Books, 1981, page 109. 

3. Cohen, Charles. "Blue-light LED joins red 
and green chip in package," Electronics, 
October 6, 1981, page 6E. 

4. Hewlett-Packard Optoelectronics Divi- 
sion — Applications Engineering Staff. Op- 
toelectronics Applications Manual. New 
York: McGraw-Hill Book Company, 1977. 

5. Seippel, Robert G. Optoelectronics. Engle- 
wood Cliffs, NJ: Prentice-Hall, 1981. 



Copyright 1 982 by Steven A. Ciarcia. 
All rights reserved. 



To receive a complete list of Ciarcia's Circuit 
Cellar project kits available from the Micromint, 
circle 1 00 on the reader-service inquiry card at 
the back of the magazine. 



April 1982 © BYTE Publications Inc 49 



How to Use 
Color Displays Effectively 

A look at the elements of color vision and 
their implications for programmers 

Color is becoming an affordable option for personal 

computers, but like any new tool, it has special 

limitations and requirements. 



John Durrett and Judi Trezona 
Center for Automated Systems in 

Education (CASE) 

Southwest Texas State University 

San Marcos, Texas 78666 



Walk into a computer store these 
days and you'll be blitzed by color: 
games with vividly colored objects 
moving amid colored textual instruc- 
tions; graphs representing many rela- 
tionships at qnce, using a different 
color for each; and screens full of 
color-highlighted text. If you're a 
veteran of the black-and-white days 
of personal computing, you'll prob- 
ably feel like celebrating. 

After spending some time with one 
of those colorful systems, however, 
your eyes may give you quite a dif- 
ferent message. Where did those 
shadows on the screen come from? 



About the Authors 

John Durrett is a psychologist and the director 
of CASE, a research center for human factors 
in automation. Judi Trezona is a freelance 
writer based in New Braunfels, Texas. 



Why is the red fading in and out? Is 
that a purple enemy shjp or a blue 
friendly ship? 

Your eyes will be telling you that 
something is wrong with the color; it 
actually seems to interfere with the 
presentation of information. Misuse 

Color vision is a 

complex process of 

three interacting 

variables: hue, 

brightness and 

saturation. 

of color is all too common in software 
designed to take advantage of this 
new small-computer capability. Like 
all new tools, color has its own 
special limitations and requirements, 
many of which are based on human 
physiology and psychology. 



Physiology of Color Vision 

The eye receives light in an area 
known as the retina. An extension of 
the brain, the retina is the most com- 
plex component of the eye. The light- 
sensitive cells within the retina are 
called rods and cones. Rods respond 
to low levels of illumination, produc- 
ing visual sensations of shades of gray 
but no color. They respond most to 
blue light and require about 30 
minutes to totally adapt to changes in 
illumination brightness. 

Cones respond to high illumina- 
tion, producing visual sensations of 
color and detail. They require about 7 
minutes to totally adapt to changes in 
illumination. Each cone is sensitive to 
red, green, or blue light; blue recep- 
tors are significantly less sensitive 
than are green and red. 

Near the retina's center is a slight 
depression called the fovea. Here, 
light has unobstructed access to the 



50 April 1982 © BYTE Publications Inc 




Photo 1: Green and yellow against a dark background can cause confusion- by produc- 
ing the sensation of shadows and afterimages with color reversal. For a demonstration, 
stare at the center of the flag for 30 seconds, then look at a blank white surface. 



cones, which cover this area and are 
responsible for sharply detailed vi- 
sion. The number of cones gradually 
decreases from maximum concentra- 
tion at the fovea toward the edge of 
the retina, where the concentration of 
rods is greatest. Because a high con- 
centration of cones produces detailed 
visual experiences, the sharpness of 
an image decreases as the distance 
from the fovea increases. 

Besides determining sharpness, the 
retinal area receiving light affects 
color perception as well. In the fovea, 
the eye is sensitive to all colors. Mov- 
ing away from the fovea toward the 
edge of the retina, red and green 
become difficult to perceive. Even 
farther from the center, yellow and 
blue become difficult to perceive. At 
the extreme periphery of the retina, 
only black, white, and shades of gray 
are perceived. 

Current Theory 

The current theory of color percep- 
tion is based on an opponent-process 
mechanism. Three opponent recep- 
tions — blue/yellow, green/red, and 
white/black — produce color sensa- 
tion by increasing and decreasing 
neural firing rates. The theory em- 
phasizes adaption, contrast, color ap- 
pearances, and afterimages to explain 
color vision. For example, since it's 
impossible to see a mixture of red and 



green in the same patch of light, these 
sensations are explained as results of 
opposite and incompatible activity in 
the same system. 

The opponent-process theory has 
several implications for programmers 
setting up color displays. If the goal is 
to convey text or graphic informa- 
tion, opponent-color combinations 
should always be avoided. Yellow on 
a blue field and red on a green field 
produce the sensation of "shadows" 
on the display and afterimages with 
color reversal. This phenomenon is il- 
lustrated in photo 1. Certain other 
color combinations are undesirable 
because the colors tend to "vibrate" 
(imagine red on blue as an example). 

These characteristics and limita- 
tions of the visual system lead to the 
following recommendations about 
color display organization: 

• Since red and green areas of the col- 
or spectrum are reduced at the edge of 
the eye's visual field, don't use red 
and green outside the normal line of 
sight or place codes in these colors 
where they're likely to be overlooked. 
If they must be used at the periphery 
of the visual field, first get the user's 
attention by making the codes blink 
before beginning continuous display . 

• For best viewing on a black 
background, always code alphanu- 
merics in red, white, or yellow. 



• Limit blue to large nonfoveal areas 
(i.e., nonfocal); blue characters are 
more difficult to read than other 
characters. 



Psychophysical Factors 

Psychophysical factors also affect 
how we perceive color. Color vision 
is a complex process of three interact- 
ing variables: hue, brightness and 
saturation. Hue is what we normally 
think of as color (e.g., red and green 
are different hues). Brightness is 
related to the intensity of light reach- 
ing the retina. Generally, higher- 
intensity light sources appear brightly 



Guidelines for Using Color 
Effectively 

Select compatible color combina- 
tions. Avoid red/green, blue/yellow, 
green/blue, and red/blue pairs. 

Use high color contrast for char- 
acter/background pairs. 

Highly saturated colors are generally 
limited on inexpensive color displays, 
so stay within the primary hues of red, 
blue and green. 

For casual users, limit the number of 
colors in one display to four. For ex- 
perienced, long-term users, up to seven 
colors may be used. 

Always code alphanumeric informa- 
tion in red, white, or yellow and con- 
fine light blue to large background 
areas. 

Since red and green are not easily 
visible at the periphery of the eye's 
visual field, code signals to be per- 
ceived in this area in white. 

Assign colors in ways that agree 
with the usual denotations. For exam- 
ple, use red for "stop" or "danger" and 
green for "go" or "all-clear." 

Incorporate shape as well as color 
when possible. This redundant coding 
improves communication and makes 
the system usable by color-blind indi- 
viduals. 

When fast responses are needed, use 
highly saturated red or blue prompts 
rather than yellow. 

If color coding has been used to 
teach relationships, use the same color 
coding when the individual is tested or 
expected to apply the learned relation- 
ships. 

As the number of colors increases, 
increase the size of the color-coded ob- 
jects. 



April 1982 © BYTE Publications Inc 51 





IJKLW40PQR 



RBCOEFGH I JKLMNOPQ 



I 



QRrnrmuT it- -i Mun&at 



Photo 2: Reduction in contrast lowers our ability to determine details, as illustrated in 
the various foreground and background color combinations. 




Photo 3a: Common denotations used incorrectly: green shouldn't be used to show deficit. 




Photo 3b: Common denotations used correctly to portray the same information. 



colored while lower-intensity light 
sources appear more dull. The retina, 
however, is also sensitive to dif- 
ferences among various wavelengths 
in the color spectrum. For instance, 
yellow is perceived as the brightest 
spectral color, while red and blue are 
perceived as the least bright. 

Saturation, which is produced by 
the interaction of hue and brightness, 
is diminished by adding white light. 
For example, a fully saturated spec- 
tral red becomes pink when you add 
white light. In terms of hue, it's still 
red, but a red of decreased saturation. 
Highly saturated colors are easiest to 
read. (Unfortunately, displays 
capable of producing saturated colors 
are among the most expensive.) 

Contrast is another variable that 
interacts with the physiological com- 
ponents of the human eye. While 
brightness is essentially a measure of 
the intensity of a light stimulus, con- 
trast is the relative brightness of 
signal over background. The greater 
the contrast, the better the readability 
of a display. In other words, darker 
colors (red or blue) are not as visible 
as light colors (white or yellow) when 
both are viewed on a dark back- 
ground. By using higher contrast, 
you produce more readable graphics. 
This phenomenon arises from charac- 
teristics of the human visual system. 
Lower contrast reduces our ability to 
determine details, as illustrated in the 
various foreground/background 
combinations presented in photo 2. 

Research has indicated that visual 
acuity depends on the size and color 
of a symbol as well as the type of 
background. In fact, symbol size 
must be increased as the number of 
colors increases. 

Another factor affecting display 
visibility is the environment in which 
a task is performed. Artificial or 
natural lighting in the work environ- 
ment can reduce foreground-to- 
background contrast. Too, sensitivity 
to color increases as the eye adapts to 
darkness. Improper lighting can re- 
sult in reduced performance, discom- 
fort, and fatigue in addition to 
limiting the effectiveness of color 
changes. Illumination surrounding a 
color-display task can have a signifi- 
cant effect on the time required to re- 



52 April 1982 © BYTE Publications Inc 




ORANGE RED 



ORANGE BLU 




Photo 4: The words are easy to read, but try naming the colors! 



spond to the displayed information. 
Response times range from fastest for 
red and blue to slower for yellow and 
yellow-orange. When programming 
games and other interactive tasks, 
consider the user's environment. 

Remember that not all individuals 
have a perfect visual system. About 6 
to 10 percent of the male population 
is color-blind, meaning that their eyes 
have defective color receptors and are 
unable to perceive certain colors. 
This factor affects less than .05 per- 
cent of the female population. Out of 
consideration for color-blind in- 
dividuals, programmers can code re- 
dundantly, i.e., use both color and 
shape for coding. 

For memory's sake, a limited 
number of color codes should be 
employed in most contexts. Users 
have recognized more than 50 colors 
with training, but the average user 
shouldn't be expected to remember 
more than 5 to 7 colors. This is the 
"magic number" usually associated 
with short-term memory (the 
memory you use to keep a telephone 
number in mind from the page to the 
dial). Novel displays should have no 
more than 4 colors, since this number 
is well below the average limit of 
short-term memory. This provides 
your brain with some memory space 
for other decision-making activities 
while the meaning of colors is being 
processed. 

Color also influences attention 



(where you are looking and what you 
are thinking about). By carefully us- 
ing color to manipulate attention, 
you can partition material at key 
points, organize it, and code or give 
meaning to it. Again, the number of 
colors used is important; having too 
many can interfere with the attention- 
gaining potential of color. You pay 
attention to the first flash of red, but 
by the tenth, it's routine. 

Our understanding of information 
can also be significantly affected by 
color. Material presented in color is 
generally processed faster than the 
same material presented in black-and- 
white. Apparently, color helps the 
computer operator organize work by 
directing his or her attention to 
what's important. No differences in 
the interpretation of information 
presented in either color or black- 
and-white are observed if adequate 
study time is allowed. 

Color can assist learning if used as 
a redundant cue or to highlight key 
concepts. However, the color coding 
of the concepts and responses must be 
matched for optimum performance. 

Common denotations of color 
should be considered when you plan 
color displays. For example, most 
people assume that red denotes 
"stop," "danger," or "down." Usual- 
ly, green indicates "go," "up," or 
"OK," and yellow means "caution," 
"slow," or "test." 

Any application of color to a 



specific task should employ these col- 
or denotations to achieve maximum 
performance. Graphics using red and 
green in ways contrary to accepted 
meanings interferes with information 
processing and can result in incorrect 
conclusions. Conversely, applying 
these two colors in agreement with 
their usual denotations actually assists 
information processing. For a clearer 
idea of this, compare photos 3a and 
3b. Photo 4 illustrates the confusion 
that can result from improper color 
coding. Guidelines for the effective use 
of color in displays are summarized in 
the text box. 

Conclusions 

Color motivates. It gets attention. 
If applied with its limitations and re- 
quirements in mind, color can be a 
powerful manipulator of our atten- 
tion, memory, and understanding. ■ 



References 

LBorges, Marilyn A., Stepnowsky, Mary A., 
Holt, Leland H. Recall and recognition 
words and pictures by adults and children. 
Bulletin of the Psychonomic Society. Feb- 
ruary 1977, vol 9(2), 133-144. 

2.Cahill, Mary Carol and Carter, Robert C. 
Color code size for searching displays of 
different density. Human Factors. June 
1976, vol 18(3), 273-280. 

3. Christ, Richard E. Review and analysis of 
color coding research for visual displays. 
Human Factors. December 1975, vol 
17(6), 542-570. 

4. Durrett, H. J. Color display systems: State 
of the art. Behavior Research Methods 
and Instrumentation. April 1979, 11. 

5.Dwyer, Francis M. Color as an instruc- 
tional variable. AV Communication 
Review. Winter 1971, vol 19(4), 399-416. 

6. Elio, Renee E. And Reutener, Donald B. 
Color context as a factor in encoding and 
as an organization device for retrieval of 
word lists. Journal of General Psychology. 
Ocotober 1978, vol 99(2), 223-232. 

7. Farley, Frank H. and Grant, Alfred P. 
Arousal and cognition: Memory for color 
versus black-and-white multimedia 
presentation. Journal of Psychology. 
September 1976, vol 94(1), 147-150. 

8.Katzman, Nathan and Nyenhuis, James. 
Color vs. black-and-white effects on learn- 
ing, opinion, and attention. AV Com- 
munication Review. Spring 1972, vol 
20(1), 16-28. 

9. Knoll, Neal E. Effects of irrelevant color 
changes on speed of name decisions. 
Quarterly Journal of Experimental 
Psychology. May 1977, vol 29(2), 277-281. 
10.Schontz, William D., Trumm, Gerald A., 
Williams, Leon G. Color coding for infor- 
mation location. Human Factors. June 
1971, vol 13(3), 237-246. 



April 1982 © BYTE Publications Inc 53 



■ 






ACCE 




Why this operating system? 

Ask the leading independent 
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enough to know it's 
an industry standard; 
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ance features. 

Ask OEM's. They'll 
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tap a vast reservoir of mass- 
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And how major software 
houses have already packed it 
with popular languages. 

And both will tell you tMat iRMX 86's 
performance and ePSt advantages are flkt 
out impressive. Which makes it a marv- 
elous match for the industry's most widely 
used VLSI microcomputers— the iAPX 
86 and iAPX 88. 



How marvelous? 
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Company 
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having to wrestle with multiprocessing 
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Most importantly, iRMX 86 is the only 
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A prime example 
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built-in software drivers are already in place. 
In fact, iRMX 86 is the only microcomputer 
operating system to support Ethernetf 
the de facto standard for local area networks 



The leading software vendors have added the 
most popular languages to iRMX 86. 



Microfocus CIS COBOL 

Digital Research CBASIC 

Intel FORTRAN 

Pascal 
PL/M 
Macroassembler 



Incidentally, all these features are 

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For a free copy of 
our article "Choosing a 
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A Human-Factors Case Study 

Based on the IBM 
Personal Computer 

Members of a human-factors evaluation team put 
the Personal Computer to the test. 



Robert G. Cooper Jr. 

Paul Thain Marston 

John Durrett 

Theron Stimmel 

Center for Automated Systems 

in Education (CASE) 

Southwest Texas State University 

San Marcos, TX 78666 



How user-friendly is the new IBM 
Personal Computer? How hard is it to 
learn to use? Will I get eyestrain from 
using it eight hours a day? Are the 
manuals complete, understandable, 
and easy to use? Does it operate effi- 
ciently for an experienced user? Are 
the error messages informative? 
These are some of the questions that a 
human-factors specialist would pose 
in evaluating any computer system. 
In this article we will use the IBM Per- 
sonal Computer as an example in 
evaluating human-factors issues in 
microcomputers. 

Microcomputers present a special 
challenge to the human-factors 
specialist because the group of 
operators is diverse and the machine 
is used for many different tasks. 
Thus, it's impossible to specify any 
single set of criteria by which to 
measure the computer's human- 
factors performance. 

We will examine here some of the 
features of the IBM Personal Com- 
puter that involve consideration of 



About the Authors 

The authors are psychologists at the Center 
for Automated Systems in Education (CASE) 
in San Marcos, Texas. 



human factors to illustrate that the set 
of criteria fluctuates. A complete 
human-factors evaluation of the Per- 
sonal Computer would be far too ex- 
tensive to present here. Our discus- 
sion should not be interpreted as 
either a complete or a representative 
assessment of the Personal 
Computer's overall quality from a 
human-factors perspective. 

We chose the IBM Personal Com- 
puter as an appropriate model for il- 

Expert users often un- 
cover new human- 
factors problems. 

lustrating the process of human- 
factors evaluation for two reasons. 
First, it is a new model and marks the 
entry into the microcomputer market 
by the largest computer manufac- 
turer. Thus, it has generated substan- 
tial interest. Second, because it is a 
new model, it will almost inevitably 
exhibit some human-factors flaws 
despite the best efforts of the 
designers and engineers. 

Evaluation Procedures 

Two kinds of information go into 
any human-factors evaluation: 



judgments made by human-factors 
specialists based on their knowledge 
of previous research and their ex- 
perience with similar systems and 
observations of users operating the 
system. 

The data collected often include: 

• types of errors made 

• frequency of different types of er- 
rors 

• frequency of consulting instruction 
manuals or seeking other kinds of aid 

• user comments about strengths and 
weaknesses of the system 

• user suggestions about needed addi- 
tions or changes to the system 

Most human-factors specialists prefer 
to draw conclusions based on em- 
pirical data collected from users of 
the specific system. However, 
because this way of evaluating a 
system is very time-consuming and 
expensive, most human-factors 
analyses, including those done at 
CASE, are based on a combination of 
the two methods. 

For the evaluation of the Personal 
Computer, we asked several types of 
users to operate the system. Some 
had experience on other systems, in- 
cluding substantial programming ex- 



56 April 1982 © BYTE Publications Inc 




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Plain — $20 Scotch — $25 Dysan — $35 

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MPI 

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perience. Some were adults — like 
many in the target market for the Per- 
sonal Computer — with little or no 
previous experience with computers. 
And some were children from age 10 
to 14 with at least some experience 
programming microcomputers at 
home or in school. 

An important group missing from 
this set of users was individuals who 
have had extensive experience on the 
Personal Computer. People with ex- 
perience on a particular system often 
have the most informative comments. 
They often demonstrate that ap- 
parent problems can be minimized 
simply by changing the operating 
procedures. Because they are compe- 
tent enough to use the full set of 
features a system offers, they often 
uncover new human-factors prob- 
lems. However, because the Personal 
Computer is so new, we couldn't find 
such a group of users, and we didn't 
have the Personal Computer long 
enough at CASE to develop such a 
group. Also, because of limited time 
and resources we couldn't test using 
standard scientific methodology. 
Rather than following a carefully 
planned procedure, we made new 
procedures as we went along, re- 
sponding to insights from the test 
group. This type of evolutionary pro- 
cess normally occurs before an actual 
human-factors experiment is con- 
ducted. Then a consistent procedure 
is established so that all participants 
are asked to do the same set of tasks. 

Hardware Characteristics 

We will begin our examination of 
the Personal Computer by looking at 
some of the human-factors character- 
istics of the overall packaging. In its 
simplest form it consists of three 
units: the computer, the keyboard, 
and the display. For many applica- 
tions, it is irrelevant whether these 
three components are integrated or 
separate. For others, separate- 
component packaging is a decided ad- 
vantage because it offers flexibility in 
choosing a display or the option of 
locating the main unit with the disk 
drive away from potentially destruc- 
tive young hands (see also the discus- 
sion of the keyboard below). 
However, for a user who must move 



the system from place to place, the 
benefits of one-piece packaging may 
bias him or her toward an integrated 
system like the Superbrain or TRS-80 
Model III. For a school system, the 
separate units are at least a complica- 
tion: three units rather than one must 
be anchored permanently to avoid ac- 
cidental damage or pilfering. 

A second characteristic, which has 
been the focus of substantial human- 



CASE 

Researchers at the Center for Auto- 
mated Systems in Education (CASE) at 
Southwest Texas State University con- 
ducted the human-factors research on 
the IBM Personal Computer discussed 
in this article. The staff of CASE is 
engaged in teaching, research, and 
development in the area of the human- 
factors considerations associated with 
computer-based systems. Although 
much of the early work by CASE em- 
phasized human-factors issues in the 
use of computers in educational set- 
tings, recent projects, including work 
for Control Data Corporation (CDC), 
Comshare, and Polaroid, encompass a 
much broader range of human-factors 
issues in computer systems. 

The procedure at CASE is first to 
define the scope for a particular 
human-factors analysis. Once the 
issues are clarified, researchers collect 
data from previously published 
human-factors studies as well as more 
general psychological studies in the 
areas of perception, cognition, and 
learning. Occasionally, previous 
research is adequate, but more fre- 
quently it is used to further clarify 
issues and design the appropriate 
research study to answer the specific 
human-factors issue being studied. 

In some ways the analysis of the 
IBM Personal Computer presented 
here is not characteristic of our usual 
research because no single task or user 
group is anticipated for the Personal 
Computer. As a result, researchers 
simulated a range of human-factors ex- 
periments that represent the kind of 
research which would be done in a full- 
scale human-factors analysis of a 
microcomputer. Thus, the general ap- 
proach and analysis presented here 
typify work conducted by groups like 
CASE on human-factors issues and 
problems in computer systems. 



58 April 1982 © BYTE Publications Inc 




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factors research, is the quality of the 
display. This of course depends large- 
ly on the monitor used. The IBM 
monochrome monitor, the only 
monitor supplied by IBM for the Per- 
sonal Computer, meets or exceeds all 
the standard criteria with respect to 
character size and clarity, screen 
brightness, freedom from flicker, etc. 
All the users we questioned were im- 
pressed by the display, even those 
who did not in general like green- 
phosphor screens. When evaluating a 
display for a large group of potential 
users (for example, for a school 
system), the criteria based on the 
results of published experiments are 
particularly useful because they were 
developed from data on a represen- 
tative sample of users. When an in- 
dividual evaluates a display for per- 
sonal use, experience with the display 
may be more useful than reading 
published results because the pub- 
lished criteria are more stringent than 
many people require. 

A third feature of the Personal 
Computer, on which a substantial 
amount of human-factors research 
exists, is the keyboard. Despite some 
of the advantages of alternate 
keyboard designs, it appears that 
American National Standards In- 
stitute (ANSI) standard and related 
keyboards (sometimes called 

QWERTY keyboards because of the 
first row of letters) will continue to 
dominate the field because of conver- 
sion and retraining expense. 
Therefore, we will examine the IBM 
keyboard from within these standard 
constraints. 

The keyboard "feel," the tactile 
sensation of typing on it, was highly 
praised by all who used it, particular- 
ly those who were familiar with other 
microcomputer keyboards. Frequent- 
ly mentioned virtues included the 
ability to move and change the angle 
of the keyboard, the sculpturing of 
the keys, and the keyboard's curved- 
plane surface. However, every user 
complained about the Enter and the 
left Shift keys (see photos la-lf). The 
Enter key is about Vi inch farther to 
the right than most users expected, 
and the left Shift key is about Vi inch 
farther to the right with the backslash 



key inserted between the Z and the 
Shift key. These unconventional loca- 
tions caused errors initially, but ex- 
tended practice usually eliminated 
such errors after about a week. 

Again, the importance of the key- 
board layout depends on the. context 
in which the computer will be used. 
For occasional use by individuals 
who frequently type on other key- 
boards (e.g., by a secretary in an of- 
fice or by someone at home who does 
a substantial amount of typing at 
work), the keyboard layout may be a 
major annoyance. For the individual 
who types mostly on the IBM 
keyboard, it should be no problem. 
Also, if the use of the computer in- 
volves nontext materials, as in finan- 
cial planning or playing games, the 
layout may be less important than if 
the computer is needed for word pro- 
cessing. 

The inclusion of an extra key be- 
tween the Z and the left Shift key may 
become standard in the future. In 
Europe, many keyboards have this 
extra key to facilitate typing extra 
characters required in some 
languages. Some word processors in 
the U.S. are using this style keyboard 
to accommodate extra functions re- 
quired in word processing. So what is 
a potential human-factors problem 
today may be an asset in the future. 
However, on several Japanese key- 
boards, it is the right Shift key that is 
moved to allow the addition of an ex- 
tra key, illustrating that no standard 
exists for these additions. 

The keyboard of the NEC PC-8001 
suggests one near-term solution. On 
this computer the user can select, 
with a single button, either an almost- 
ANSI-standard keyboard (with the 
right Shift key out of place) or a 
keyboard with the letters in 
alphabetical order (which is helpful 
for young children). This flexibility 
could be expanded to let users pro- 
gram the arrangement of their own 
keyboards. 

Documentation 

Human-factors considerations are 
especially significant in the area of 
documentation. Minimally, docu- 
mentation needs to fulfill three func- 



60 April 1982 © BYTE Publications Inc 



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Photos la-lf: Comparisons of keyboards. All have letters in the same position, but note the variation in the placement of the Shift, 
Return, and other special symbols. Note also the various solutions to the problem of where to put all the keys not needed on ordinary 
typewriters. 



tions: initial training in using the 
system, quick reference for momen- 
tarily forgotten information, and 
complete documentation of capabil- 
ities and how to access them. Ideally, 



many other functions will be served, 
including guidance on uses for system 
features, information to aid in debug- 
ging (including common errors and 
their symptoms), etc. 



The manuals for the Personal Com- 
puter have received very high praise. 
Gregg Williams in "A Closer Look at 
the IBM Personal Computer" 
(January 1982 BYTE, page 36) wrote, 



62 April 1982 © BYTE Publications Inc 



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"They will set the standard for all 
microcomputer documentation in the 
future." Our analysis of the manuals 
is less enthusiastic, although in many 
ways the documentation is excellent. 

We will take a look at the BASIC 
manual first to illustrate some of the 
strengths and weaknesses of the 
documentation. The manual is for 
reference and does not claim to be a 
programming tutorial. For its stated 
purpose the manual is quite good. All 
users who had prior knowledge of 
BASIC had no difficulty program- 
ming on the Personal Computer, in- 
cluding using some of the special 
features of IBM's version of BASIC. 
The features of the manual that are 
most useful are the index and the brief 
and extended descriptions of every 
command, statement, and function. 
The extended descriptions are most 
complete for those features that are 
unique to IBM's BASIC and include 
informative examples. 

There are five parts to each 
keyword description: format, ver- 



sion, purpose, remarks, and example. 
The only drawback is that some in- 
formation is omitted, apparently 
because it does not fall neatly into 
any of the categories. For example, 
restrictions and probable error 
messages from mistakes are only in- 
cluded in some of the descriptions. 
For the FOR and NEXT statements, 
information about errors is given in 

IBM has left the market 

for tutorial manuals to 

outside publishers. 

the body of the remarks section, and 
no information is given at all about 
restrictions on the amount of nesting 
or about overflow in nesting, which 
will lead to an "out of memory" er- 
ror. Despite these problems, the 
manual can be used effectively. 

As adequate as this manual is for 
the experienced user, it does not fill 
the need of the novice for an instruc- 
tion manual. General instruction 



manuals do exist (e.g., Basic BASIC 
and Advanced BASIC), but the 
idiosyncrasies of different BASICs 
have led to a demand for instruction 
manuals for individual machines. Ac- 
cording to our observations, novice 
IBM users had much greater difficulty 
with IBM's reference manual than do 
novices starting out on an Apple II 
Plus with Apple's instruction manual. 
IBM apparently made a conscious 
decision to leave the novice market to 
the independent producers of com- 
puter manuals and books. An IBM 
spokesperson assured us that such in- 
dependent sources are already hard at 
work and their manuals should be out 
shortly, but until such manuals are 
written, a hole remains in the 
documentation from the perspective 
of the computer novice. 

In the interim, IBM could make 
two simple additions to the current 
manual that would be helpful. One is 
a quick-reference card that could be 
removed from the manual; it would 
decrease the need to flip back and 



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64 April 1982 © BYTE Publications Inc 



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forth from the brief- to extended- 
description sections of the manual. 
Second, a comment could be added to 
the preface about the existence of Ap- 
pendix D, which discusses the dif- 
ferences between IBM Personal Com- 
puter BASIC and other BASICs. 
None of our novice users discovered 
this appendix within the first hour of 
trying to learn to program in BASIC 
(we showed it to them after an hour), 
and such information would have 
been very useful in trying to use the 
general manuals for BASIC. Of 
course, these changes would be useful 
for more experienced users also. 

IBM's Guide to Operations 
presents a similar problem. It appears 
to be written for novices and contains 
excellent illustrations and very clearly 
written instructions. However, 
crucial pieces of information are 

IBM's monochrome 
monitor meets or ex- 
ceeds all the standard 
human-factors criteria 
for video displays. 

either left out or have odd locations 
in the manual. For example, we had 
several novices set up the computer 
from scratch. Perhaps because we 
were watching with notepad in hand, 
all followed the written instructions 
scrupulously. As instructed on page 
2 — 6, they turned on the system for 
the first self-test after connecting the 
keyboard and power cord. Four out 
of five continued on to page 2 — 7 and 
began to connect the cables for the 
display and printer without first turn- 
ing off the system, and would have 
done so had we not stopped them. 
Next, the manual calls for the use of 
the diagnostic disk on page 2 — 16 
without any cautions about the 
handling of disks. This information is 
contained several pages later. None 
of our novices mishandled the disk. 
But if they had mishandled it and 
were looking in the problems section 
because the disk would not load, the 
warning there would obviously be 
too late. 

Because the Personal Computer we 
used for our evaluations had a defect 



prtfvccd this tilttti *h t.HwMlMiitli 
eslcr nsui tor. The AWlt'S 

40- c h a rat 1 « r line wa s i e s i $ n * •& t $ i ! } m 
tht sis t of TiJ'S an* iatxptnsiv* c$l$r 
aonitors uith thtir iwtr ftftftiuUftft,. 
The larger letters are easier to reii 
Mi loner resolution displays. 
JALSO, WITHOUT" THE LOWER-CASE ADAPTER 
THE ALL CAPITAL FORMAT IHPROUES 
LEGIBILITY TOO. OF COURSE* AH APPLE II 
Cm BE ECOJIPED WITH AN 86-COLOflH 
ADAPTER AMD USED WITH A HIGH RESOLUTION 
'MONITOR.. 



2a 



The IBM Personal Coaputer Basic 

Version Al.BB Copyright IBM Corp. 1981 

34049 Bytes free 

Oh 

10 print 'This is the IBM Personal Coaputer aonochroae Monitor" 

20print "All the screens froa the other computers were photographed 11 

30 print "at the save distance froa the screen." 

run 

This is the IBM Personal Computer aonochroae Monitor 

All the screens froa the other coaputers were photographed 

at the saae distance froa the screen. 



2b 



6: ABC PAGE 1 LINE 8 COL 81 

LmmUm*i.u. I.**, i »..;.... i..,.) i i i 



This is the Monitor froa a Xerox 820 Information Processor 
Tha screen size is alraost identical to that of the IBM 
Personal Cooaputer. As is apparent in the photograph the 
color of the phosphor is different. Soae people prefer 
one type over the other, but there is no clear consensus. 



2c 



Photos 2a-2e: A representative sampling of computer video displays. 



66 April 1982 © BYTE Publications Inc 




2d 



This display is from a Micro-Term Mime-2fl terminal. It is representative of 
the quality of display that the users of large computer systems are accustosed 
to seeing. Some microcomputer users connect a terminal like this to their 
system for a variety of reasons, including the quality of the display. 



2e 



in the power supply and disk system 
when first received, we noticed 
another documentation problem. We 
had decided to have a novice unpack 
and set up the system. He progressed 
through the setup procedures to the 
point of loading the diagnostic disk, 
which wouldn't load. In response to 
this failure he repeated all the 
previous steps, looping through the 
procedures twice. He then turned to 
the section "Problem Determination 
Procedures/' This proved fruitless 
because, by the time he reached page 
4 — 7, he was reassured that the 
system was working because it met 
the criteria of correct information on 
the screen and correct auditory 
response (one short beep). At this 
point our novice gave up. It took 



another eight minutes for the "ex- 
perts," who had been observing, to 
discover on page 4 — 8 the statement 
"Error messages may or may not re- 
main on screen. So look quickly." An 
error message had flashed on and off 
shortly after the power was turned 
on. 

Two documentation requirements 
illustrated here are that warnings, 
cautions, and other crucial informa- 
tion should appear very early in the 
manual before the relevant error can 
be made and that error conditions 
ought to lead to a permanent message 
that is terminated only by user ac- 
tion. 

We discussed the problems de- 
scribed in the last two paragraphs 
with people from IBM and the local 



Computerland store. Both com- 
mented that the Personal Computer is 
not being sold by mail order and that 
a purchaser would be given substan- 
tial training before taking the com- 
puter home. Although this may lessen 
the necessity of the above re- 
quirements in some ways, we do not 
believe it eliminates them. It is poor 
practice to leave the task of convey- 
ing such important information to a 
group over which IBM has little if any 
control. In addition, people other 
than the original purchaser may need 
to learn to use the computer. Instruc- 
tion manuals should be complete and 
sufficient to allow one to learn and 
use the system in isolation, even if 
this is not the ideal context for learn- 
ing. 

All the IBM manuals fit in 8V2- by 
5V2-inch, hardcover, three-ring 
binders. The advantages of this for- 
mat include easy updating. Sections 
are added to the Guide to Operations 
each time a new option (e.g., com- 
munications interface or printer) is 
added to the system. However, there 
are some negative human-factors 
consequences of this format. Three 
times during our testing, a manual 
was dropped in such a way that the 
binder came open and pages fell out. 
For a home or business user, this 
would probably be only an occa- 
sional annoyance. However, in a 
school setting these manuals would 
not be acceptable. Something more 
durable is required. The specific use 
for which the system is intended will 
determine whether this is a significant 
human-factors failing. 

IBM does have some human- 
factors problems with its manuals for 
the Personal Computer. However, 
compared to documentation that 
other new computers have had when 
they were first introduced, the IBM 
manuals are outstanding. And they 
compare favorably even with the up- 
dated offerings from other manufac- 
turers. 

Operational Characteristics 

A human-factors evaluation of the 
functional operation of the Personal 
Computer is the most difficult to do 
without a specific task in mind and 



April 1982 © BYTE Publications Inc 67 




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without a long period of time in 
which to observe users trying to ac- 
complish this task. Also, an examina- 
tion of the individual features of the 
Personal Computer reveals that many 
of the best features from microcom- 
puters of other manufacturers have 
been incorporated. A separate ex- 
amination of each feature in terms of 
how it helps facilitate people's ability 
to use the system would start to 
sound like an IBM press release. 
However, the Personal Computer's 
versatility (in itself a human-factors 
asset) does entail human-factors 
costs. For example, many individuals 
have happily used their microcom- 
puter for years without being 
bothered by lack of precision or by 
rounding errors. On the other hand, 
the use of some computers for 
business bookkeeping is problematic 
because of limited precision. The IBM 

The error message 

appeared on the 

screen so briefly the 

operator never noticed. 

Personal Computer (and several 
others) offers the choice of single or 
double precision. This is an advan- 
tage to business users but requires a 
decision by other users ("Is 6-digit 
precision enough, or do I need 177"). 
Some users may find that they prefer 
the old situation in which they obtain 
9-digit precision (sufficient for home 
bookkeeping) automatically and do 
not have to make the determination. 
The system reset procedure on the 
Personal Computer provides a dif- 
ferent perspective on the problem of 
assessing human factors without a 
specific context. For purposes of com- 
parison, it is important to be aware of 
the human-factors problem with the 
system reset ori the Apple II. On the 
Apple II, an operator would push the 
key labeled Reset, an extremely sim- 
ple procedure. Unfortunately it was 
too simple, and because the Reset key 
was directly above the Return key, it 
often occurred accidentally. Apple 
corrected this problem on the more 
recently produced versions by giving 
the user the option of choosing to re- 



68 April 1982 © BYTE Publications Inc 



Circle 149 on inquiry card. 



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quire a control key plus Reset for a 
reset to occur. 

On the Personal Computer, the 
operator initiates a system reset by 
holding down the Control and Alter- 
nate keys and then pressing the Delete 
key. This procedure is certainly 
cumbersome enough that it is unlike- 
ly to occur by chance. Is it too 
cumbersome? Because the operator 
uses three keys, none of which is 
labeled Reset, will the procedure be 
forgotten by those who need to use it? 



Without considering a specific con- 
text we can't answer these questions, 
but we can consider the kind of 
criteria a human-factors specialist 
would use in answering them for 
some particular context. First, how 
frequently is a system reset executed? 
If it occurs extremely rarely (as might 
be the case for someone using already 
developed software), it probably is all 
right if the command is forgotten and 
the user has to look it up. If it is used 
quite frequently (perhaps in debug- 







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70 ApriJ 1982 © BYTE Publications Inc 






Circle 416 on inquiry card. 




ging complex programs), it will be 
remembered because of the constant 
use. If it is used occasionally, it may 
be hard to remember and yet be 
frustrating to have to look up each 
time. Second, what are the conse- 
quences of making a mistake when 
trying to execute a system reset? If 
delay in a reset or if some combina- 
tion of related keys might lead to dire 
consequences in some application, 
then for that application the Personal 
Computer would have a major 
human-factors failing. Third, what 
alternatives are available and how do 
they interact with other human- 
factors characteristics of the system? 
For example, a separate key could be 
used as on the Apple II, but that 
either adds another key to the 
keyboard or takes up a key that 
might have been used for some other 
function. Too many keys produce an 
added memory load on the human 
operator, just as multi-keystroke 
commands do. The human factors 
trade-offs here must be evaluated in 
terms of the way the system will be 
used. 

The Personal Computer has ten 
special-function keys called "soft 
keys," which have a set of default 
functions but can be changed by the 
user. The "soft keys" are a very 
popular characteristic among the ex- 
perienced users we questioned. 
However, because the keys can be 
redefined, they are labeled Fl through 
F10 — not very effective labels for 
remembering their functions. The 
Personal Computer solves this prob- 
lem by displaying partial labels at the 
bottom of the screen (for all 10 keys 
on an 80-column display and for the 
first 5 on a 40-column display). We 
expect that those operators using a 
television display (40 columns) and 
others not wanting the labels at the 
bottom of the screen will tape a list of 
the ten functions somewhere near the 
computer. In some ways it would 
have been nice if space had been left 
on the keyboard for labeling these 
keys. However, that would have had 
the undesirable effect of enlarging the 
keyboard. Again, there are always 
trade-offs. 

The relation of the line-editor pro- 



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gram that is part of the disk operating 
system (DOS) to some of the charac- 
teristics of BASIC is another human- 
factors issue. Using the line editor, for 
example, the Personal Computer lists 
lines 100 to 200 with a command of 
the form "100, 200 L" and deletes 
with a command of the form "100, 
200 D". In BASIC, lines are listed 
with a command of the form "LIST 
100-200" and deleted with a com- 
mand of the form "DELETE 100-200". 
The difference in syntax adds a 
memory burden for no intrinsic 
reason to anyone who uses both 
capabilities of the Personal Com- 
puter. An experienced user who was 
asked to use the line editor had trou- 
ble with the syntax. On the second 
day he used it he made errors and 
had to go to the manual to check the 
syntax of the commands. This syntax 
problem is a relatively minor issue 
when considering the line-editor pro- 
gram and BASIC but is representative 
of the more general class of dif- 
ferences in syntax that can lead to 
disastrous mistakes (not necessarily 
on the IBM machine). Perhaps the 
best example of syntax-function 
problems is that of commands for 
copying: on some systems the source 
is first and the destination second, 
whereas on others the reverse is true. 
Errors that were the product of mov- 
ing from one system to the other can 
and have resulted in the loss of crucial 
files. 

Conclusions 

We have illustrated the process of 
human-factors evaluation of 
microcomputers and its importance. 
Understanding that the user is part of 
the system is crucial to understanding 
the human-factors approach. Just as 
no single language is best for all pro- 
gramming, no single system design is 
best for all users. We have presented 
some general principles that apply to 
all systems but, for the most part, 
evaluations must take into account 
requirements of the specific, potential 
user. Groups like CASE, which per- 
form human-factors evaluation, start 
by determining the requirements of 
the user, then they evaluate the 
human-factors characteristics of the 



hardware, software, and documenta- 
tion in terms of those requirements. 

Because user needs vary so, it was 
almost certain that the IBM Personal 
Computer would have some human- 
factors failings; it could not be all 
things to all people. Although we did 
not attempt to perform a complete 
evaluation, our overall impression of 
the human-factors design of the Per- 
sonal Computer is very positive. IBM 
has begun to put substantial emphasis 
on human-factors design, and the 
IBM Personal Computer exhibits 
many positive results of the efforts of 
human-factors specialists. However, 
some of the simple and easily changed 
human-factors failings that we un- 
covered could have been detected 
from relatively simple observations 
of users. 

If you are considering purchasing a 
microcomputer, these comments 
have two major implications. First, 
be clear about the use or uses to 
which the system will be put, and 
then concentrate on human-factors 
characteristics that are relevant to 
those uses. Do not buy a computer 
that will be used primarily for word 
processing on the basis of the en- 
thusiastic recommendation from 
someone who uses his for home 
finance and playing games. Second, 
get as much information on the actual 
use of the system as possible. Use it 
yourself in the way you intend to use 
it; do not just go through a set of 
demonstration programs, even if they 
are designed to illustrate the features 
of the programs you will be using. 
Try to find someone who is already 
using the system in an application 
similar to the one you anticipate. As 
mentioned previously, we find ex- 
perienced users to be one of the best 
sources of human-factors insights. If 
you make use of the insights of 
others, you may avoid being the 
source of negative human-factors in- 
sights about your own system. ■ 



Acknowledgment 

BYTE would like to thank Computerland 
product manager Richard Mandel and the 
Austin, Texas, Computerland store for equip- 
ment and assistance provided during the 
preparation of this article. 



72 April 1982 © BYTE Publications Inc 



Circle 248 on inquiry card. 








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do not know is that Intertec may very well offer the best 
customer protection programs in the industry. What is 
customer protection? It's a totally new, comprehensive 
product and customer support program which virtually 
guarantees your long term satisfaction with every new 
Intertec product you buy. It means that if you are not satisfied 
with your Intertec purchase, you can get your money back at 
any time during the original factory warranty.* Or, in the 
unlikely event your equipment should become inoperative 
during the first few weeks of the warranty period, we will 




FEATURES 



• True multi-user capability— network 

up to 255 users. • Up to 1 .5 Million bytes of 

local, off-line user storage. • Four models of user 

workstations available. • 64 K Internal memory in each 

workstation. • A CP/Mf operating system. 

• 10 — 384 Megabytes of auxiliary disk storage. 






COMPUSTAR 



TM 



replace it for you! And we'll even provide a reimbursement 
allowance to cover your cost of returning the system to us. 

Go ahead. Review the pricing and performance specifi- 
cations of all the microcomputers available today. We think 
you'll agree with us. . . ours are still the best! If you want 
uncompromised performance, competitive pricing, sophisti- 
cated expandable products and just plain peace-of-mind, 
you'll want Intertec. 

Ask your dealer about Intertec's SuperBrain and 
CompuStar microcomputer systems. Or, call or write us at the 

tCP/M is a registered trademark of Digital Research, inc. 



address below and get more information on today's best 
values in single and multi-user microcomputer systems. 

=fl[SINTRTEC 
=ESY5TEMS® 

2300 Broad River Rd./Columbia, SC 29210 
(803) 798-9 100/TWX: 810-666-2115 

Circle 214 on inquiry card. 



Hardware Review 



The Hewlett-Packard 
Interface Loop — HPIL 

Unique Two-Wire System Allows 
Low-Cost Data Collection 



Robert Katz 

248 East 90 St. #3B 

New York, NY 10028 



The most intriguing feature of the Hewlett-Packard 
HP-41C has been the multiple plug-in port on the unit's 
back (see Steve Leibson's "The Input/Output Primer, 
Part 3," page 186). Until now, four ports have been 
available for plug-in RAMs, ROMs, a card reader, a ther- 
mal printer, and a bar-code reader. Yet users have been 
begging for the chance to let the HP-41C talk to the out- 
side world. Hewlett-Packard is very protective of its pro- 
ducts and does not publish specifications of the connec- 
tions to these ports. Justifiably, because the calculator's 
delicate CMOS (complementary metal-oxide semicon- 
ductor) circuitry can be damaged easily by improper con- 
nections. 

The public demands and Hewlett-Packard responds. 
By announcing the Hewlett-Packard Interface Loop (HP- 
IL), Hewlett-Packard has provided users with much more 
than they've been requesting. The HP-41C was a quan- 
tum leap beyond conventional calculators, and, 
remarkably, the HPIL is a quantum leap for the HP-41C. 

The Loop Hardware 

HPIL operation is powerful and sophisticated, but the 
hardware is simple, small, and easy to interconnect. A 
board called the HPIL Module (HP82160A) plugs into 
any of the four ports on the back of the HP-41C. The 
module receives its power from the HHC's internal bat- 
teries. Two 71-cm (28-inch), 2-wire cables extend from 
the module; at their ends are 2 -pin male and female con- 



About the Author 

Robert Katz, who prefers to be called "Bob," is a recording engineer for 
records, TV, and radio. He also dabbles in computers. 



At a Glance 

Name 

Hewlett-Packard Interface Loop (HPIL) 

Manufacturer 

Hewlett-Packard 

1 000 Northeast Circle Blvd. 

Corvallis, OR 97330 

Price 

HP82160A HPIL Module: SI 25, available now; HP82183 Extend- 
ed I/O ROM: price to be announced, available summer 1982; 
HP82180A Extended Functions/Memory Module: $75, available 
now; HP82181A Extended Memory Module: S75, available now; 
HP82166 HPIL Converter: $395 for a prototyping kit including 2 
converters, test board, HPIL cables and manual, or S 1250 in quan- 
tities of 10 with no accessories, available spring 1982; HP82182A 
Time Module: $75, available mid- 1 982; HP82161 A Digital Cassette 
Drive: $550, available now; HP82162A Thermal Printer/Plotter: 
$495, available now; HP3468A Programmable Digital Multimeter: 
$695 plus $125 for battery option, available now; HP82938A 
HPIL Interface Card for HP Series 80 Personal Computers: $295, 
available now; 

Description 

HPIL is a complete software and hardware system that turns the 
HP-41C handheld computer/calculator into a general-purpose, data 
collection, measurement, and analysis tool as well as an equip- 
ment controller. 



Other features 

Simple 2-wire connectors. 



'transparent" operating system 



Hardware options 

Digital Data Cassette, Thermal Printer/Plotter, Programmable 
Multimeter, GPIO Interface, Computer Interface, among others 

Audience 

Original equipment manufacturers (computer-aided 
manufacturingj, instrumentation manufacturers, hobbyists, others 



76 April 1982 © BYTE Publications Inc 



^Lenjoy the problem-solving 
power of APL language 
on your Apple computer 

Solve engineering, scientific, or business problems easily—write finished applications software in 
a fraction of the time you'd take to write similar programs in BASIC, FORTRAN, or COBOL. . . 
and do it all with your Apple® right at your desk. 




Test your language against APL/V80™ 

To compare APL/V80's clear concise code with the language you're now using to solve problems, 
take this short programming test. Here are three common problems, showing the APL/V8Q solution 
for each. Program your best effort for each problem in the language you use now. Now compare the 
number of lines and keystrokes needed to achieve a solution in your language to the APL solution. 
Keep in mind the APL/V80 solution shown contains not only the computation commands, but also 
every instruction needed to input required data , as well as all the commands to print out the results. 

Problem 1: 

Write a program to input a list of values (List "A"), sort the list from lowest to highest values, 
then print all the values in list A in ascending order. 

APL/V80 solution: Solution in your present language: 

/JE14+Q] (Hint: Usually this takes two loops and 15 to 

20 statements.) 
Problem 2: 

Write a program to input a list of values (List "X") and compute the standard deviation for the 
list values. 

APL/V80 solution: Solution in your present language: 

(( + /(jr-( + /;n*ff)*2)*-l+ff<-p;r-K])*.5 ( Hint: Th ' S takeS at least 0ne ' 00 P and about 

16 statements.) 
Problem 3: 

Write a program which will compress adjacent spaces to a single space, with possible multiple 
occurences, in a string of characters called TEXT. 

APL/V80 solution: Solution in your present language: 

(LCHT)*!!?-^ '=TEXT)/TEXT+\H ? 



Whether you're an engineer, scientist, educator, 
or businessman, now you can solve problems faster 
than ever using your Apple®. With APL/V80™ from 
Vanguard Systems Corporation, search for solutions 
in a fraction the time you thought possible. Get 
the added benefit of creating programs which are 
not only easier to write, but also are easier to under- 
stand, modify, and explain. 
Solve your problems faster 

APL/V80™ is the most concise powerful program- 
ming language available for computer solutions to 
scientific and business problems on Apples (or 
CP/M®-based computers). When you have APL/V80, 
you can focus your attention moreon problem-solving, 
and concern yourself less with the details of program 
coding. APL/V80 lets you develop functional soft- 
ware, and debug it, in about one-fifth the time you 
need to program a solution in other languages. 

If you're an APL user already, you'll appreciate 
knowing we developed APL/V80 for the Apple with 
the ISO-ANSI proposed APL standard in mind. All 
future enhancements will be guided by developments 
in this standard, so APL/V80 programs maximize 
compatibility with other APL systems. 
More than a language: a new world of convenience 

APL/V80 is more than a language. . .it's a whole 
new world of convenience for you and your Apple. 
A variety of special features and auxiliary processors 
give you problem-solving power unmatched by any 
other language available for the Apple. 
Powerful auxiliary processors included 

The Graphics Processor gives you full access to 
Apple's high resolution graphics from APL. You can 
print to any ASCII device, including plotters, through 
arbitrary input and output modes. Our system vari- 
able quad-AV gives you all the characters any APL/ 
ASCII device can print, plus all 32 ASCII control 
characters, APL overstrikes, underlines, lower-case 
letters, and special control characters for full-screen 
applications. The Utility Processor gives you memory 
access and processor calls to both the 6502 and 
the Z80, so APL/V80 can access virtually any Apple 
system ROM or peripheral card. Our CP/M Input 
File Processor lets APL/V80 read and work with 
any CP/M file. 



workspace goes even further, transforming your Apple 
into a wizard of an APL terminal. WSIS uses the 
workspace Interchange Standard format to transfer 
application workspaces in from or out to other APL 
systems. This gives you the power to move APL 
programs developed in one version of APL into 
another. 
Amazing APL power for your Apple 

If you already use some version of APL on a 
mainframe, a time-sharing service, or a minicomputer, 
you may wonder how useful APL/V80 can be in an 
Apple-size workspace. Our answer: you'll be amazed! 
To give you utmost memory availability, APL/V80's 
auxiliary processors occupy memory only when loaded. 
By using our )CSAVE and )CC0PY commands to 
move functions and variables into and out of a work- 
space, you can run applications far larger than your 
workspace. Also, APL/V80 makes auxiliary proces- 
sors you develop more powerful. By offering a variety 
of supervisory services, APL/V80 lets your AP's write 
error messages, read input, convert data, do string 
search and compare, or even halt processing upon 
error discovery. 
Minimum hardware required 

APL/V80 for the Apple requires a 48k Apple II 
with autostart ROM, or Apple II+, one disk drive, 
a Z-80 SoftCard, and either the Language Card, 
RamCard, or some other compatible 16k memory 
extension card. 
To learn more, act now 

No matter what problemsyou'resolving, APL/V80™ 
can help you solve them faster, more easily. If 
you'd like to know more, send us the coupon below. 
APL/V80 does so many things, in a single page we 
can hardly begin to tell all the ways it can help you. 
Write today for the full story of APL/V80 for your 
Apple. 

NOTE: Specifications subject to change without 
notice. Apple design, Apple II, Apple II+, and Lan- 
guage Card are trademarks of Apple Computer, Inc. 
CP/M is a trademark of Digital Research. SoftCard 
and RamCard are trademarks of Microsoft. 
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= Contact your local Apple dealer for a demonstration of APL/V80 and get your copy today. If you don't 5 
E have a local dealer, use this coupon to order direct from us now: Please rush the items ordered below. = 
5 I understand all items are normally in stock and available for immediate shipment: 



An Input Stack Processor lets you spool input 
commands for later execution. Our APL File Proces- 
sor gives you an indexed file system. The WSFNS 
workspace makes APL/V80 compatible with common 
functions from standard mainframe APL versions, 
plus some non-standard functions such as string- 
searching and extended formatting. Workspace FILE- 
FNS gives you the most commonly used facilities 
of file systems found on large timesharing services 
such as LP. Sharp and STSC. 
Make your Apple a wizard of a terminal 

Appropriatesettings of APL/V80's system variable 
quad-TT, combined with your modem, let your Apple 
communicate with other computers. The APLTERM 



More information about APL/V80 for Apple 
APL/V80™ User's Manual - Enclosed is $30. 
Complete APL/V80 • Apple Software Package 

Enclosed is $500. Please send me an end- 
user license, object code disk, documentation 
manual, and special APL character generator. 
Software PLUS RamCard - Enclosed is $675. 
Software PLUS Z-80 SoftCard - Enclosed is 
$850 



= Enclosed is my check for $ 

| OR Charge to: □ MasterCharge □ Visa 

| Ship to: Name 

| Address 

= City 



□ Software PLUS Z-80 SoftCard PLUS RamCard 

Enclosed is $995 

□ Complete Hardware - Software system - APL/ 
V80 - Apple Software PLUS Apple 11+ 48k 
computer with APL character generation card 
already installed PLUS Apple Disk Drive, 
PLUS NEC 12" video screen PLUS SoftCard 
PLUS RamCard. Enclosed is $3195. 

D As above with second Disk Drive - Enclosed 
is $3695. 

date 



Card f 

Signature . 



exp. 



.State. 



Phone. 
— Zip. 



VanguarcI Systems! 

M^^^w^w^ 6901 Blanco Road = 

V^llRri San Antonio, TX 78216 

^^^^■^|^# (512) 340-1978 | 

■iiiiiiiiiiiiiiiiiiiiiiimiiiiimiiiiimiiiiiiiiiimiimHiiNiiiiiiiiiiiiiiiiiiiiiiniiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii 



Circle 423 on inquiry card. 



A Day in the Life of an HP-41C 

/ prefer to call my HP-41C an HHC. That way I 
don't have to call it a ''calculator" or a "computer. " 
Hewlett-Packard calls it both a "calculator" and a 
"system." Actually, the versatile HP-41C can be 
treated any way the user desires. Its power and flex- 
ibility are illustrated by the following tour of the HP- 
41C world. 

It's morning and I find no cash in my pockets. No, 
the HP-41C cannot mint money, but its continuous 
memory can tell me how much I have in my checking 
account. Upon pushing RCL (recall), the legend RCL 
appears in the alphanumeric liquid-crystal display. To 
the right, two prompts (cursors) can be seen; these 
prompts are the HHC's signal to supply a two-digit 
number in response. Since data register 9 contains the 
amount of my checking account balance, I punch 
and 9. The HP-41C answers with $127.59000. 

I only need to display two digits after the decimal, 
so I push SHIFT for secondary key functions, then FIX 
and 2. Each key gives a satisfying "thunk" when 
pressed; tactile feedback has always been a Hewlett- 
Packard feature. The display is even more helpful by 
naming each button's function as it is pushed. It's also 
easy to cancel or correct a function if a mistake is 
made. By using the back arrow key •— , the screen 
unambiguously shows each correction, and HP-41C 
error messages appear in English. 

I see that I have exactly $127.59 in my checking ac- 
count. Before deciding to deplete the account, I run 
downstairs to check the just-delivered mail and happi- 
ly discover the arrival of a check for $300. Pushing 3 
STO + 09 adds the $300 to my checking account (at 
least within the calculator). In addition, I push £ + 
and see the number 12, marking the twelfth deposit I 
have made since I began to count deposits in the Sigma 
registers. The Sigma registers can compute the mean 
(average) of all my deposits, the standard deviation, 
and other statistical functions. To find the mean, I 
push XEQ (for execute or run,) and then spell out 
M-E-A-N. This ability to call a function by spelling out 
its name is very much a computer-like action. 

After stopping at the bank, I head for the recording 
studio where I work as an acoustical consultant and 
maintenance man. Arriving at the studio, I discover a 
volume unit (VU) meter that reads too low. I apply a 
sine wave to the recording console's input; 2.0 volts 
(V) are measured across the output terminals, yet the 
meter reads VU. Thanks to a program I've written, 
my HP-41C can talk to me in English and clue me in to 
the decibel error of the meter (see listings 1 and 2). I 
can call this program in two ways. One way is by 
name as above: XEQ d-B-V, and the program begins 
running. Since I use the dBV program a lot, I reduced 
the keystrokes to a single one via the USER mode. 

In USER mode, the HP-41C is customized for in- 
dividual use; programs or functions can be reassigned 



to any keys. The entire keyboard can even be recon- 
figured if desired, then returned to normal by a second 
push of the USER key. An added attraction is a 
keyboard overlay which allows you to identify 
reassigned keys with stick-on labels. Thus, a small, 
uncluttered keyboard can call literally hundreds of 
functions. 

Throughout the course of the morning, I will use 
several HP-41C functions and two other programs. 
When the job is done, I attach the HP-41C to one of 
many available accessories, a battery-powered ther- 
mal printer. With the aid of still another program, it 
prints out an invoice of parts and labor performed on 
this job. 

On the way to the next job, a friend and I play a 
game of Hangman on the HP-41C. This game is in- 
cluded in the Games Pac, which is designed to help 
while away those between-business hours. More 
serious Standard Module Pacs are available to help 
perform engineering and scientific tasks, among 
others. The average application module price is $35. 
The COPY function permits copying any program 
from ROM (read-only memory) to RAM (random- 
access read/write memory) to allow customizing. For 
example, I have added personalized prompts to the 
game of Hangman. 

Listing 1: A single key depression in USER mode executes 
the author's program dBV. The calculator first prompts for a 
voltage entry; response is 2.0 V, and the RUN key is pressed. 
The calculator asks for reference voltage; 0.775 V is assumed 
if RUN is pressed. The answer is 8.2 dB over 0.775-V 
reference. Next, the program is run with a different reference 
voltage (1.23 V, which is 4 dB above a one-milliwatt 
reference across 600 ohms). The answer is 4.2 dB over 
1.23 V. Another key depression in USER mode executes the 
author's program VOLTS. The calculator indicates that 
1.55 V is 6 dB over 0.775 V. The display is formatted to two 
decimal places but can easily be changed. 

XEQ "dBV" 
VOLTS? 

2.6 RUN 

REF?R/S=STHD 

RUN 

8.2 dB/0.8 V 

XEQ "dBV" 

VOLTS? 

2.0 RUN 

REF?R/S=STND 

1 . 23 RUN 

4.2 dB/1.2 V 

XEQ "VOLTS" 

dB? 

6.00 RUN 
REF?R/S=STNB 
RUN 
1.55 V/0.77 



78 April 1982 © BYTE Publications Inc 



Don't . 
with your 
business! 





Invest in an M System 



''Okay, which entry-level, single- 
user microcomputer should I own?" 
The BOS M System. 
"Which multi-user system should 
I own?" 

The BOS M System. 
"If I want a larger system with the 
ultimate in performance and 
capacity, what should I own?" 
The BOS M System Multiprocessor. 
"How much more does it cost to 
own a single-user set-up and 
upgrade it, than to start with a 
larger system?" 
Not a penny more. 
"Can I have diskette, tape, and 
large rigid disk storage?" 
Yes. 



"How about really good accounting 

software?" 

The MBSI* package (GL, AR, AP, 

PR, OE/INV, Sales Analysis — all 

in Cobol) is probably the best 

available on any system... this is 

one you have to see to believe. 

"How about Word Processing?" 

WordStar tm, and others. 

"Can I run all the other software 

I've seen?" 

Yes, if it's CP/M* * * compatible, 

almost certainly! 

"Will I have to change the 

operating system when I expand?" 

No, withBOS/TURBODOS****, 

just upgrade it. 




"Well, this is important... will 

service be available when I need 

it?" 

Yes, with a large dealer network, 

strategically placed maintenance 

depots, and fast factory repair 

turn-around. 

"Sounds great! But isn't it too good 

to be true?" 

No. . .and it's not even expensive! 

So, why take a chance with 

somebody else? 

"Gkay, how can I get one?" 
Contact your dealer, systems 
house, or consultant — or call us 
toll-free! 



Dealer and OEM 
Inquiries Welcome 




Business Operating Systems, Inc. 
2835 East Platte Avenue 
Colorado Springs, Colorado 80909 
In Colorado Call: (303) 634-1541 
Toll Free Number: 1-800-525-3898 



Circle 63 on inquiry card. 



APPLICABLE INDUSTRY STANDARDS; S-100 IEEE 696 • RS 232, HDLC, SDLC, Async, Sync • CP/M*" • TURBODOS' * " • 8" soft sectored diskettes • ANSI X3/B5/15 Tape Ca tridge 
•Micro Business Software, Inc. • * 'Trademark of Micropro Int. Corp., San Rafael, CA • * * 'Registered Trademark of Digital Research • " * 'Software 2000, Inc. 



The powerful programming ability of the HP-41C is 
enabled by an extended version of the RPN language 
that Hewlett-Packard introduced to the public in 1971 
with the world's first handheld scientific calculator, 
the HP-35. Over 130 scientific functions and 56 pro- 
grammable flags are available, some of which keep 
track of the status of peripheral devices as well as con- 
trol the peripherals status. While all previously made 
calculators were hardware-intensive devices, the HP- 
41C is a software-intensive device. As such, each plug- 



Listing 2: A single key depression in USER mode executes 
the author's program PTOF (pitch to frequency). The calcu- 
lator asks for the note, and the operator responds with "B 
Flat/' one octave below middle C. The answer is 223 Hz; the 
note and its octave are also given. Next comes a printout of 
the first 22 steps of the PTOF program. Note the compact 
nature of the RPN code. Each line's interpretation follows: 
01 — ALPHA Label; 02 and 03 — store loop control number in 
register 00; 04 and 05— store ALPHA string in register 01; 
06— display format with no digits following the decimal; 07 
through 09 — these steps display the PROMPT shown above; 
10— the operator's note is stored in the X register; 11— clear 
flag 22, the digit entry flag; 12 through 14 — these steps 
display the second PROMPT shown in the running program; 
15 through 17— if flag 22 is clear, store in register Z. Other- 
wise, store the octave number there; 18 through 22 — some of 
the alphanumeric manipulations available to the HP-41C 
user. A complete listing of this program is available from 
Hewlett-Packard's Users' Library. Write to Hewlett-Packard, 
Corvallis Division, 1000 Northeast Circle Blvd., Corvallis, 
OR 97330 for information on how to join the Library. 



Text continued from page 76 

nectors. The cables are simple stranded wire; gauge is of 
little importance. Cable lengths can be up to 10 meters 
between devices when using simple stranded wire. 
Distances of up to 100 meters are possible with twisted, 
shielded, pair wire. Each HPIL peripheral (e.g., printer or 
data cassette) is equipped with two corresponding mating 



in module adds completely new functions, giving the 
HHC a new personality. 

Hewlett-Packard has taken a lot of care in naming 
functions so one can remember them easily, but if I 
forget the name of a function and don't have the in- 
struction manual handy, I'm not helpless. I can call up 
a CATALOG, a directory of the many functions 
available. Three such catalogs exist in the HP-41C (see 
listing 3). Usually this list is enough to jog my 
memory. 

The future of the HP-41C is virtually unlimited. If 
there were enough demand, a higher-level language 
such as FORTH or even BASIC could be implemented 
in a plug-in ROM. However, I find that the versatility 
of RPN eliminates the need of a higher-level language 
in most applications. A BASIC interpreter would run 
markedly slower than RPN. FORTH might be faster 
than BASIC, but the experienced user soon discovers 
that new functions can be added in a remarkably 
FORTH-like manner. 



Listing 3: A printout of the HP-4lCs CATALOG 1 function, 
which lists all user programs in RAM, including the number 
of bytes required. Total room used here is 1148 bytes. Ap- 
proximately 1064 bytes are free in the HP-41CV for more 
user programs, an astounding amount of storage ability for 
an HHC. 



XEQ "PTOF" 


07 


"NOTE?" 


NOTE? 


08 


RON 


BF 


09 


PROMPT 


RUN 


10 


OSTO X 


OCTOVE?R^S=© 


1 1 


CF 22 


-1 RUN 


12 


"OCTOVE? 


233 HZ, BF/- 




R/S=0" 


i 


13 


OOFF 


PRP " " 


14 


PROMPT 




15 


FC?C 22 


Bl+LBL "PTO 


16 





F" 


17 


STO Z 


02 .605 


18 


XEQ 05 


03 STO 00 


19 


ORCL Y 


04 "CDEFGO" 


20 


OSTO Y 


05 OSTO 01 


21 


RSHF 


06 FIX 


22 


OSTO T 





CAT i 


LBL'HEK 




EHB 


268 BYTES 


LBL T PT0F 




END 


283 BYTES 


LBL ¥ «V 




LBL'VOLTS 




LBL'dBH 




LBLWTS 




END 


292 BYTES 


LBL7 




EHB 


62 BYTES 


LBL'FREe 




EHB 


19 BYTES 


LBt'PfiR 




LBL'RPfiR 




EHB 


37 BYTES 


LBL'HfiHG 




EHB 


262 BYTES 


.EHB, 


33 BYTES 



connectors. Extension cables are available from Hewlett- 
Packard. 

Plug the two loose cables into the side of the peripheral 
and you're ready to go. If there is more than one 
peripheral, connect the devices in a sort of daisy chain. In 
this loop, information passes from a sending device 



80 April 1982 © BYTE Publications Inc 



Look What Apparat has 
for your IBM Personal Computer, 





The following 
add-ons are 
available 
immediately: 

• 2 Dual Headed 40 Irack Drives - (appears as 
four) 640K of storage, software patch, easy 
internal mount. $630.00 

• Combo Card - Parallel printer, ASYMC 
communication (RS-232), and clock calendar 
functions, uses only one slot. $279.00 

• 2 Single Headed 40 Irack Drives - 320K of 
disk storage, easy internal mount. $450.00 

• 48K additional RAM - 27 chips plug into 
master PC board $75.00 

• Add-on Memory Card — (uses 64K dynamic 
RAM chips), 64K - $425.00, 128K - 
$525.00, 192K - $625.00, 256K - $725.00 

• Prom Blaster — Programs mostlKto4K 
EPROMS of 25XXand 27XX single or 
multivoltage, personality modules, read/write 



software. $149.00 

• Apparat Qame Diskette — 
$24.95 

• Clock Calendar - Features 
seconds, minutes, hours, day of 
week, date, month and year, 
backup battery, leap year and 
crystal time base. $129.00 

• Prototype Card — 3.5 by 8 inch wirewrap 
holds 150-14 pin dips. $29.95 

• RQB Color Monitors — Includes cable, 16 
color modifications, NEC - $1,095.00, 
AMDEK - $899.00, TECO - $699.00. 

• 3rd and 4th Add-on Drives — Expansion 
cabinet and IBM compatible drives, cabinet 
and 1 drive - $499.00, two drives - $749.00 

• 64K Hardware Print-Spooler — Parallel printer 
adapter, buffers 13 minutes of output at 80 
characters/second. $399.00. 

• EPSON MX Printers - MX-80 (with dot 



addressable 
graphics) ■ — 
$499.00, MX-80 F/T 
- $575.00/ MX-1Q0 - 
$775.00 
• Verbatim Datalife 
Diskettes - (5-1/4" 40 track, 
'^^W' box of 10) $24.95 

• 16K Memory Kits (9 chips) - 
$25.00 

• 5-1/4" Flip-Sort - $21.95 

• 5-1/4" Plastic Library Case - $1.95 

Apparat will continue to develop add-on 
products for your IBM Personal Computer. Call 
today for more information. Dealer inquiries 
welcome. 

(303) 741-1778 

IBM Personal Computer is a trademark of IBM. 



Apparat, Inc. 

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Photo 1: The HPIL Module. 




Photo 2: HP-41C connected to an HPIL Module, Digital 
Cassette Drive, and Thermal Printer/ Plotter in the loop. 




Figure 1: The HPIL is a continuous loop, with data and instruc- 
tions traveling from an originating device back to that device for 
a complete, bit-for-bit error check. 



through all the other devices. When data return to the 
source, they are completely checked for errors (see 
photos 1 and 2 as well as figure 1). Since each succeeding 
battery-operable device uses its own power to retransmit 
the data it receives, total power in the loop is shared 
equally, minimizing battery drain. All communication 
between devices is supervised by the HPIL Module, 
which is now available for $125. 



Circle 431 on inquiry card. 



HPIL Specifications: The New Firmware 

As mentioned earlier, plugging a ROM into the HP- 
41C gives it a new personality. The HPIL Module is no 
exception. Within it are the routines essential for turning 
this portable, programmable calculator into a versatile 
"outside world" controller. Three types of HPIL routines 
are supported: printer-type operations (also suitable for 
video display and for controlling external devices); mass 
storage operations (for digital cassette or disk drive); and 
interface control operations (largely used for controlling 
external devices). 

The HP-41C as controller can address each device in 
the loop by a unique number. The HPIL Module is 
capable of addressing up to 30 devices in the loop, cer- 
tainly a quantity large enough to satisfy most users. If 
that's not enough, the addition of a module called the Ex- 
tended I/O (Input/Output) ROM will allow the HP-41C 
to extend its address capability to a total of 961 devices 
on the loop. If still more devices are needed, loops can be 
connected through an HPIL Converter. (Each loop, 
however, must have its own controller.) The Extended 
I/O ROM has additional capabilities which I'll discuss 
later. 

The calculator/controller designates which peripheral 
is to be a sending device (called a talker) because there 
can be only one talker at a time. The other devices on the 
loop become listeners. When so instructed, listeners can 
also act upon data passing through. For example, a 
printer can print information, a video display can display 
it, etc. 

Hewlett-Packard does not intend to publish the actual 
voltage levels or the digital nature of the commands used 
within the two-wire HPIL loop. It has revealed that the 
HPIL communicates with the outside world through the 
HPIL Converter, a general-purpose interface board 
designed to be attached to the user's GPIO (general- 
purpose input/output device) equipment. For example, 
an original equipment manufacturer (OEM) may wish to 
install an HPIL Converter within its electronic voltmeter, 
enabling the voltmeter to be programmed by an HP-41C 
or other computer. Hewlett-Packard intends to aid other 
manufacturers by providing all the details necessary for 
them to successfully communicate with the HPIL Con- 
verter. An overview of converter hardware connections 
will be presented in a later section. 

An Asynchronous Communication Loop 

Quite a few more essential details are known about the 
loop's protocol. The HPIL is an asynchronous com- 
munication loop whose speed self-adjusts to that of the 
slowest active device in the loop. For example, if a slow 
printer is connected within the loop but is not to be used, 
the controller can instruct the printer to ignore data/in- 
structions and pass them on to the next loop device. That 
way the loop can operate at its fastest possible speed. The 
Extended I/O ROM will even allow a means for the 
Digital Cassette Drive to pass data to the printer through 
an essentially inert HP-41C. In this mode, the HP-41C 



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will become a relay device rather than a controller and 
will not retard loop operation. 



HPIL Speed 

Just how fast is the HPIL loop? Depending on cir- 
cumstances, it can approach speeds of 40,000 bps (bits 
per second). While this is many times faster than most 
RS-232C serial links, the HPIL can be slower than the 
parallel-based IEEE-STD-488 bus. (Originally known as 
GPIB or HPIB for Hewlett-Packard Interface Bus, the 
present IEEE-STD-488 was developed by Hewlett- 
Packard.) The HPIL is intended to be a low-cost, non- 
competitive alternative to IEEE-STD-488. The HPIL is 
competition, however, for the more antiquated RS-232C. 
Just the fact that the HPIL uses only two wires gives it a 
definite advantage; then there is the availability of an 
HHC as a controller. 

Let's look at the speed of this asynchronous loop in 
more detail. Since instructions as well as data are sent 
around the loop, the instruction cycle of the controller 
may become a significant factor. In almost all cases, the 
loop controller will be the HP-41C portable calculator. 
While microcode (machine language) runs through the 
HP-41C at a speed of about 350 kHz, the practicalities of 
the Macro Instruction Interpreter effectively make an in- 
structi°n cycle much slower. An instruction such as 
ENTER!, originally keyed into program memory by the 
operator, takes about 40 ms to execute. This includes the 
overhead of the Instruction Interpreter and the HP-41C 
Operating System. Therefore, practical data throughput 
speed will probably average about 150 bytes per second 
(1200 bps). The 40,000-bps HPIL maximum could only be 
managed by, for example, an HP-80 series computer run- 
ning a machine-language controller program or by con- 
trollers Hewlett-Packard is now developing. 



Using the Loop 

Operation of the loop can be completely transparent to 
the user. When a printer is in the loop, the operator (or a 
running program) simply executes a PRINT function; the 
HPIL searches for the first available printer to perform 
the function using a unique feature called an accessory 
poll. Optionally, the operator (or a program) may 
specify a particular printer by means of the SELECT func- 
tion. In this case, the operator becomes only a little more 
involved with HPIL operation. 

Manufacturing plants may wish to have the HPIL con- 
trol a set of relays and read a number of indicators. The 
HP-41C is ideally suited to that task. Its alphanumeric 
capabilities and versatile keyboard allow programs to be 
written so that they can talk to the plant operators in 
plain English while performing complex underlying 
operations. 

Efficient firmware in the HPIL Module is available, 
allowing a user to perform READ/WRITE functions onto 
a mass storage device (such as the Hewlett-Packard 
Digital Cassette Drive) or PRINT functions. Firmware 
supports either the Hewlett-Packard printer or any 
ASCII-compatible standard printer having a parallel 
port. Using less efficient instruction methods, the present 
firmware also allows the HP-41C to query and change the 
status of relays, monitors, voltmeters, or hundreds of 
other devices. 



More Efficient I/O Operation 

The Extended Input/Output ROM plugs into the back 
of the calculator and will add the following functions to 
the firmware: 

• Extended addressing of up to 961 devices on the loop 

• User access to all additional functions involved with 



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Listing 4: The DIRECTORY that leads every HP digital cassette. 
Owners of the Card Reader will be interested to know that file 
ALL is a WRITE ALL file containing the complete status of an 
HP-41CV. This file loads in about 25 seconds as opposed to the 
several minutes and inconvenience of using over 10 magnetic 
cards. More than 50 files of this size can be stored on one 

cassette! 

SIR 

HflHE TYPE REGS 

m PR 39 

STfiTUS KE 1 

TEST ST 16 

Nil Uh 336 

PTO PR 29 

dBV PR 42 

Z PR 9 

control and query of external devices attached to the loop 

• A routine to enable bar-code generation on the new 
HP82162A Thermal Printer/Plotter 

•A routine to allow one or more cassette copies to be 
generated; especially valuable when distributing software 
or data for OEM use 

• An external device will be able to "call" the controller 
for service requests 

The HP82183 Extended I/O ROM will be available by the 
summer of 1982, with price to be announced. 

Extended Functions/Solid-State Mass Memory 

The HP82180A Extended Functions/Memory Module 
adds firmware as well as additional read/write memory 
to the HP-41C. While this new product is not directly in- 
volved with HPIL operations, it is being introduced now 
in an effort to make the HP-41C a more "friendly/' ver- 
satile controller and, of course, an even more powerful 
HHC. HP-41C owners not interested in controlling exter- 
nal devices can still make use of the Extended Func- 
tions/Memory Module. First, this device adds 47 new 
functions not included in the HP-41C mainframe. 
Second, the HP82180A and two companion Extended 
Memory Modules can increase the solid-state memory 
space of the calculator by 4.2K bytes to a whopping, 
handheld total of 6.2K bytes. 

Many users will look forward to a programmable 
ASSIGN function, which will enable special-purpose 
keys to be automatically assigned and later cancelled 
within specific programs. Previously, key assignments 
had to be executed manually. Note that the software- 
intensive design of the original HP-41C is what makes 
these post-production enhancements possible. 

Another extended function allows alphanumeric 
manipulations previously manageable but relatively 
cumbersome in the standard HP-41C. For example, the 
leftmost character of an alphabetic string can be iden- 
tified by a program and then acted upon. The 104-step 
program PTOF (partially described in listing 2) could be 
reduced to approximately 80 steps and would run faster 
with the new extended functions. 

Additional memory of 889 bytes is contained in the 



HP82180A; its companion, the HP82181A Extended 
Memory Module adds 1666 bytes. Two HP82181A units 
can be used at any one time. With all three modules plug- 
ged in, 4221 bytes of extended memory are available to 
the user. The additional 4.2K-byte memory is called ex- 
tended memory to distinguish it from the resident 
memory of the HP-41C. Extended memory is not online 
in the sense that programs can be executed directly or 
that data can be used directly. Instead, the new 
read/write memory is organized in a file and register for- 
mat, just as on a disk drive and with equivalent access 
speed. 

For example, two completely different specialized cal- 
culators could be kept in solid-state storage and down- 
loaded into the main RAM on demand. ASCII data of up 
to 4221 characters could be collected and stored in the 
field to be acted later on by the HHC, by a computer, or 
transferred to the new Digital Cassette Drive. It will not 
be necessary ' to "wipe" information in main RAM in 
order to move data from the extended memory to the 
Digital Cassette Drive. Data within the extended memory 
can also be sorted, alphabetized, or otherwise organized 
at disk-access speeds. The HP82180A Extended Func- 
tions/Memory Module is now available for $75, as is the 
HP82181A Extended Memory Module. 

Industry Reaction to the HPIL 

The HPIL is certainly a versatile system, but what's the 
catch? For now, there is one little catch: other manufac- 
turers may design peripherals to attach to the HPIL, but 
the only loop controller presently available is a Hewlett- 
Packard product. Therefore, a turnkey system would 
contain at least two Hewlett-Packard products — the 
HPIL Converter and an HPIL controller. The company 
says that the converter hardware will support controller 
operation. Unfortunately, the software to run a con- 
troller is very complex, causing concern over possible im- 
proper HPIL operation. Nevertheless, manufacturers 
who wish to develop a controller for the HPIL may con- 
tact Hewlett-Packard for details. Despite the Hewlett- 
Packard monopoly on the controller, the HPIL will pro- 
bably become popular with other manufacturers simply 
because the versatility of Hewlett-Packard's most power- 
ful calculator makes it the ultimate controller. 

HPIL Peripherals: The Digital Cassette Drive 

To me, the most intriguing new peripheral is the 
Digital Cassette Drive. Using digitally certified magnetic 
tape, it is truly a mass storage device (see photo 2). Up to 
131,072 bytes of online mass storage will fit into a small 
cassette similar in size to an audio microcassette. The 
drive itself is compact, and its flip-top cover contains a 
convenient storage space for two cassettes. The magnetic 
storage is 50 times the size of the HP-41CV RAM and, ac- 
cording to Hewlett-Packard, contains enough mass 
memory to accommodate all the programs from the 26 

HP-41 Solutions Books onto one tape. If this is not 
enough online capacity, HPIL firmware even allows 
"chaining" of multiple drives. The user or a running pro- 



86 April 1982 © BYTE Publications Inc 



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Photo 3: With the HP-41, HP82160A, HPIL Interface Module, 
HP-85, and HP82938A HPIL Interface Card, portable data col- 
lection, direct data transfer, and sophisticated data analysis are 
made easy. 

gram simply calls a file by its name. The HPIL firmware 
searches the directory at the head of each cassette until it 
finds the selected file, then loads the file from that drive 
into RAM. 

The cassette drive is of digital quality. It records data 
with parity, and a VERIFY function is available to check 
for errors. Being HPIL compatible, it can be addressed by 
controllers yet to be developed for the loop. Powered by 
rechargeable batteries, the drive has a standby power 
mode feature, especially valuable where operation on 
batteries and without human intervention is expected for 
long periods. The controller automatically calls a 
POWER UP function when it wishes to access the cassette 
drive. As a result, this unit is truly field operable. 

Using a two-track format, the cassette drive is bidirec- 
tional (one track per direction) with two speeds: 23 cen- 
timeters (9 inches) per second read/write speed and 76 
centimeters (30 inches) per second search/rewind speed. 
For those concerned about potential head wear at these 
speeds, the company asserts that the tape-to-head 
pressure is so light that head wear is insignificant. Data 
density is 335 bits per centimeter. Format is 256 bytes per 
record, with 512 records available per cassette. 

When a file is called, the machine first reads the direc- 
tory at the head of the cassette for the location of the 
named file (see listing 4 for an example of a tape direc- 
tory). Then the cassette rapidly (76 cm/s) winds to the 
file and reads it back to the HPIL. Before writing a file, 
the machine looks through the directory to see if the 
name already exists. If so, it will rewrite (record over) 
that file. If not, and if space is available on the medium, it 
will add the new file name to the directory, speedily jump 
to the free spot on the tape, then record the new file, all 
under HPIL control. 

Seven different types of files may be recorded: Pro- 
gram, Data, Key Assignments, Status (condition of the 
HHC — useful for reestablishing conditions after a run- 
ning program has been interrupted), Writeall (entire con- 
tents of the calculator), ASCII, and Unknown. 



To check the effective speed of the cassette drive, I 
recorded and then read back a Writeall file (2352 bytes). I. 
timed the machine from the moment I pressed the last key 
of the READ ALL command to the time the read was com- 
pleted. It took 27.5 seconds; therefore, effective average 
speed of data transfer using cassette is 85.5 bytes per sec- 
ond (684 bps). The read/write speed on the medium is a 
respectable 963 bytes per second, but, as you can see, 
tape-cuing time must lower the real speed considerably. 
The same amount of information could be loaded from a 
typical disk drive in a couple of seconds. 

New Thermal Printer 

Probably the most important feature of the new ther- 
mal printer is its HPIL capability, which allows it to be 
addressed by future controllers and computers. The 
HP82162A Printer/Plotter includes all the features of the 
earlier HP82143 as well as the ability to print bar code. 
Since it too runs on rechargeable batteries, a standby 
power mode is included. 

For those who are unfamiliar with the earlier printer, 
its features include: ASCII standard upper and lowercase 
characters and special characters, double-wide printing 
option, a 24-character line, user-definable characters, 
and plotting capabilities. HP-41C users should im- 
mediately see the potential of the HPIL interface plus 
printer plotting — an input signal can now be plotted in 
real time. 

More HPIL Peripherals 

The HP3468A Digital Multimeter (DMM) is program- 
mable through the HPIL. Its 12-character alphanumeric 
display can output messages generated by the controller 
or by the DMM. Resolution is adjustable from 3 to 5 
digits, with increased resolution resulting in a propor- 
tional trade-off in speed. 

The HP82938A HPIL Interface Card shown in photo 3 
plugs into the Hewlett-Packard Series 80 personal com- 
puter. The computer will then be able to take control of 
the loop. It can also be programmed to store and analyze 
data collected on the calculator. ROMs for the Series 80 
machines are compatible with the HPIL Interface Card, 
allowing the computer to use the printer, cassette drive, 
and all future HPIL peripherals. 

The HP82182A Time Module plugs directly into the HP- 
41C. This will allow the unit to be turned off and then 
"awakened" automatically by the timer's programmable 
ALARM function. The program will start running the 
line at which the HP-41C was positioned when it was 
turned off (or when it turned itself off). Since OFF is a 
programmable function, the process can be repeated in- 
definitely. The timer becomes especially useful in a con- 
troller situation, allowing measurements to be taken at 
regular intervals, devices to be turned off, pressures 
regulated, etc. This module can also display time and 
date and provide calendar data over a 2738-year span. 

The HPIL Converter 

The key to the HPIL's success will be the availability of 



88 April 1982 © BYTE Publications Inc 




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Photo 4: The HPIL Converter (4.5 by 11 by 2 cm) connects the 
HPIL loop with the outside world. 



the HPIL Converter. This component (see photo 4) is 
designed to interface the HPIL with the outside world. 
OEMs may wish to build HPIL capability into com- 
ponents such as measurement instruments, enabling pro- 
grammable control by an inexpensive HHC rather than a 
much more costly computer. 

BYTE readers who have connected hardware to com- 
puter input/ output ports are probably familiar with a 
VIA (versatile interface adapter) or a PIA (peripheral in- 
terface adapter). Applying a similar philosophy, the 
HPIL Converter is a much smarter device. The converter 
contains the necessary firmware to recognize HPIL 
instructions and to convert specific instructions and data 



from the serial HPIL format to a dual 8-bit parallel for- 
mat. As a matter of fact, one of the sample schematics 
presented in the converter manual is an interface with a 
Centronics-style parallel printer connector. 

Hewlett-Packard supplies a 34-pin printed-circuit-type 
mating connector; a standard ribbon connector will also 
work. Power for the HPIL Converter ( + 5 V DC at 90 
mA) is derived from the host device. All input/output 
lines are TTL-compatible and include two bidirectional 
8-bit ports, three input handshake lines, three output 
handshake lines, and several special-purpose lines. The 
latter are used for triggering external devices and for 
communicating special conditions such as power down, 
power up, or service request. Complete hookup details 
for programming negative or positive logic strobes, full 
or half duplex operation, and more are furnished in the 
HPIL Converter documentation. 

Some Revisionist Thoughts 

The addition of all this hardware to the Hewlett- 
Packard arsenal poses a couple of logistical problems. 
The first problem concerns battery charging; there are 
too many plugs and not enough sockets. The HP-41C, 
printer, and cassette drive each come with identical-style 
power connectors. A power transformer and a charging 
cable are also furnished with each unit. It is certainly 
inconvenient to have to find wall sockets for all these 
devices. I hope that Hewlett-Packard relieves the conges- 



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nOVATIVi 

s o f t w a ' plications 




The Plaz 
1150 Chestnut Lane, Mento Paik, CA 94025 
P.O. Box 2797, Menlo Park, CA 94025 
Tel (415)326-0805 




90 April 1982 © BYTE Publications Inc 



Circle 208 on inquiry card. 



i imji 



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CPU for twice the performance. The LNW80 
outperforms all computers in its class. 



MODEL I COMPATIBiLlfY-The LNW80 is 

fully hardware and software. compatible with 
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Circle 237 on inquiry card. 




Photo 5: Hewlett-Packard's HP82163A Video Interface connects a monitor or TV to HP's interface loop. This permits handheld 
computers like the HP-41C — previously limited by a single-line display — to display information in a 16-line by 32-character video 
format. Aided by the new interface (available by the end of 1982), HP-41C owners can review up to 16 program steps at a time. 



tion by introducing a charger capable of powering several 
peripherals at once. 

The second logistical problem is more serious. Hewlett- 
Packard has supplied a "horn of plenty" in modules, but 
there are only four sockets to receive them. A user may 
very well need to operate several of these modules 
simultaneously. Hopefully, the company will soon sup- 
ply a "piggyback module adapter" of some sort to relieve 
the problem. Outside of the above, very few complaints 
can be made about Hewlett-Packard's well-supported 
products. 

The Future 

With the introduction of the HPIL Loop, Hewlett- 
Packard has made a commitment to issue a series of new 
HPIL controllers, peripherals, and instruments. Expect to 
see in the near future a video/TV monitor interface 
(shown in photo 5), an 80-character/line impact printer, 
an HPIL/RS-232C converter, and a self-powered version 
of the GPIO board designed for the home hobbyist. No 
official corporate announcement has been made at this 
writing, but Hewlett-Packard probably will introduce 
these items before the end of the year. 



I'm sure someone will ask about word processing with 
the HP-41C and the HPIL. It's conceivable but not 
without an external keyboard since the HP-41C is only 
good for "hunt and peck" typing. Its alphanumeric 
capabilities and portability will lend themselves to many 
other unique jobs in the very near future. 

Conclusions 

As usual, Hewlett-Packard's documentation is ex- 
cellent. Prototypes of the new products must have been 
in use within the Corvallis, Oregon, plant for a con- 
siderable length of time because the style of the instruc- 
tion manuals reflects much experience with the products. 

With any new and complicated product, there are 
bound to be bugs. The ones I have found so far have been 
minor. My experience is that Hewlett-Packard's Corvallis 
Division will respond to consumer complaints quickly 
and efficiently. 

The potentials of the HPIL loop are literally awe- 
inspiring. As such, it is difficult for me to make an overall 
evaluation other than that the future looks bright. I sug- 
gest you read on to page 94 and delight in what's just over 
the HPIL horizon. ■ 



92 April 1982 © BYTE Publications Inc 



c_ tnn CTQTir mcmhqu OQCQi/Tijoru tnj 
_/ iuu jmiiL i il i iui 1 1 ui i li ii ii i n iuuui i 




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16K STATIC RAM $169 64K STATIC RAM $795 



32K PARTIALLY POPULATED $479 48K PARTIALLY POPULATED $659 



Finally, you can buy state-of-the-art 
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computer at unprecedented savings. 

Memory Merchant's memory 
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These memory boards are not kits, 
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SHIPPED DIRECT FROM 
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All Memory Merchant's boards are 
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Prices, 



NO RISK TRIAL 

We are so convinced that you will 
be absolutely delighted with our 
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boards, you may return it (intact) for 
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NEW 18 MONTH LIMITED 
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The reliability of our boards, through 
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HOW TO ORDER 

Please send check, money order, 
VISA or MASTERCHARGE (add ICA#) 
with your order. Sorry, no C.O.DIs. 
Specify model number, and quantity 
desired. Shipping and handling 
charge is $5.00 per board. California 
residents add 6% Sales Tax. Credit 
card purchases may be telephoned 
to (415) 483-1008. 
OEM and DEALER inquiries invited. 

[jjl„ mcmof v 
mM merchant 

14666 Doolittle Drive 

San Leandro, CA 94577 

(415) 483-1008 

terms, specifications subject to change without 
Circle 252 on inquiry card. 



64K RAM, Model MM65K16S 

Cool running operation to 10 MHz 

Ultra low-power consumption 
Fully loaded 64K board draws: 
Typ. 350 Ma. (Max. current 550 Ma.) 

Bank Select Capability 

Extended Addressing Capability 

One 16K submodule equipped with a 
2K window which may be located 
in any of the 2K segments 

2716 (5V) EPROM Compatibility: 
Programmed 2716 EPROM's may 
replace any or all of the RAM 

Four independently addressable 16K 
submodules on one board organized 
as two pair of independent 32K 
banks or as one 64K Extended 
Address Page. Each 32K bank 
responds independently to phantom. 
Bank Select logic is compatible 
with either Cromemco Cromix* or 
standard Bank Select software. 

*Cromix is a trademark of Cromemco. 

New 16K (2K X 8) 150ns Static RAM 
Runs on any S-100, 8-bit system 
MPM Conversion Option: Write for details. 

16K RAM, Model MM16K14 

Bank Select Capability 
Extended Addressing Capability 
One 4K segment equipped with IK 

windows 
Four independent 4K X 8 byte 

segments 
Uses field proven 2114 (IK X 4) 
Low-power consumption (Typ. 1.3 Amps) 
Runs on any S-100 8080, 4 MHz 

Z-80 or 5 MHz 8085 system. 

notice. 



The A 1 13 Interface puts 
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to work 
in the 
Laboratory 

For Only 

$550 





You can plug 
this powerful interface 
easily into your Apple Computer 

and create a fast, flexible 

analog data acquisition system 

with all these features: 

• 16 independent input channels 

• Ranges from lOOmVto ± 5V, selectable by software 

• 12-bit precision, 0.024% accuracy 

• Fast 20 -microsecond conversion time 

• Sample-and-hold circuitry captures changing signals 

• External trigger mode responds to commands from 
remote equipment 

• Software diskette included, to get you started right 
away 

A I 13 comes with a 1 -year warranty and is backed by full 
technical support. It is part of a full line of iS analog and 
digital systems, all inexpensive and modularly designed 
so that you can select and pay for only the interfaces and 
functions you need. 

Interactive Structures has been designing and producing 
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of IS units are in use internationally. One is being used in 
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the NASA Space Shuttle. 

Write or call now for more information on the A I 1 3 — 
the best investment you'll make in a research assistant. 

' Recommended (J S list priceearh 

Apple is a registered trade name of Applet Computer Inr Circle 464 On inquiry Card. 



Interactive Structures, Inc. 

112 Bala Avenue 

P.O. Box 404 

Bala Cynwyd, PA 19004 

(215)667-1713 




A Future Day in the Life of an HP-41C 

It's morning (February 1, 1983), and I find no cash in 
my pockets. No, the HP-41C cannot mint money, but 
it can call the bank for me and engage in a friendly 
conversation with the bank's computer. I plug the 
Modem Management Pack into a blank slot and con- 
nect the HP-41C to an HPIL converter which in turn 
has been hooked up to a telephone coupler. I quickly 
learn that the check from Detroit finally cleared, and 
my checking account is good for $1000. 

Later, I arrive at the recording studio and discover a 
faulty VU meter (things haven't changed much). I am 
now carrying a powerful tool consisting of my trusty 
HP-41C attached to an HPIL Converter, an A/D 
(analog-to-digital) converter, and a long cable ter- 
minating in alligator clips. These components make up 
not just a programmable multimeter, but a complete 
measurement and analysis system customized by the 
user — me! 

The HHC tells me that there is 2.0 V across the con- 
sole's output terminals, which represents 4.2 dBs 
above the reference of 1.23 V. I suspect an intermittent 
connection, so I've programmed the HP-41C to beep 
whenever a change in level occurs (a high-frequency 
beep if the level goes up, low-frequency if it goes 
down) and to display the new voltage and dB level. 
When I wiggle a loose resistor on the circuit board, the 
HP-41C cheerfully beeps to signal the cause of the pro- 
blem. Even in 1983, cold solder joints and bad connec- 
tions cause the majority of service problems. 

My next job is rather distantly located, but this time 
the HP-41C is not available to play Hangman. It has a 
much more important job to do — it's helping to fly my 
Beechcraft. You see, back in 1981, the Hewlett- 
Packard company produced a custom ROM for the 
Beech Aircraft Corporation, turning the HP-41C into a 
revolutionary flight -planning system capable of saving 
thousands of gallons of fuel a year. Well, today 
(1984 ?) this system has been updated so that the plane 
is equipped with an HPIL Converter. Since instrument 
data is now transmitted directly to the HP-41C, the 
pilot does not need to key in information about fuel 
flow, speed of descent, wind velocity, or air speed. 

Of course, as soon as I get the money, the next step 
will be to purchase the HP -41 C Auto Pilot. By 1985, I 
will be able to plan my flight at home on the portable 
HP-41C, carry it with me to the airport, and plug it in- 
to the control panel of my airplane. Thus, it will help 
me in the air and continue to serve me on the ground. 

The preceding ''science fiction" story is based entire- 
ly on components that are available today and on 
technology that is completely within reach. We have 
only begun to dream. 



isllll 




4 



m 



Designed especially for the Apple II, the Supercolor RGB Board comes complete 
with connecting cable for Electrohome ECM-1302 RGB Monitors- for outstanding 
overall video quality. You select any 16-color combination from 256 available colors, 
for pure white text plus color in a 'Hi-Res' mode. Efficiency was never so colorful. 




*-■<>•- r i 



wmBBSSSam 



m 



ELECTROHOME 



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Consumer Computer Mktg. Inc., Sudbury, Mass (617) 443-5128 
Components Unlimited Inc., Lynchburg, VA (804) 237-6286 
EMES Systems Ltd, New York, NY (800) 223-1799 

Circle 164 on inquiry card. 



Anthem Systems Company, Burlingame, CA (415) 342-9182 
Mycrosystems Distributors Inc., Dallas, Ifexas (214) 669-9370 
Computerland, SanLeandio, CA(800) 772-3545 (Ext. 118) 
Outside California (800) 227-1617 (Ext. 118) 



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[ 



Hardware Review 



Strawberry Tree's Dual 

Thermometer Card 

for the Apple 



Dr. William Murray 

RD #3, Box 363 
Montrose, PA 18801 



If you've ever needed to monitor temperatures over an 
extended period of time, then Strawberry Tree's Dual 
Thermometer Card is for your Apple. Actually, the card 
is part of a complete package that also contains a disk, 
two thermometer probes, and a user's manual. 

The thermometer card has an internal clock that can be 
set when the system is loaded, or, if a clock/calendar 
card is present in the system, the clock can be set 
automatically. This feature enables your Apple to record 
the time at which temperature data is taken. Data-sam- 
pling intervals can also be set to occur at any preset time 
by means of the internal timer. The current temperature, 
along with the maximum and minimum, can be recorded 
for each probe and stored on disk or sent to a printer as 
output. 

Everything in the package (see photo 1) is first class, 
which helps justify the retail price of $260. The card has 
fully socketed integrated circuits (ICs) and gold-plated 
edge connectors. The 83-page manual covers virtually 
every topic from installation to software modification. 
The software is a refreshing departure from many Apple 
peripherals on the market today. It is usable, under- 
standable, and can be modified if necessary. 




H lU 



-,,,-' -w^; &gg , 



Photo 1: Strawberry Tree's complete package of temperature- 
monitoring equipment for the Apple. 



96 April 1982 © BYTE Publications Inc 



Circle 265 on inquiry card. 



THE $595* 
SMART TERMINAL 



The Heath 19 Smart Video Terminal gives you all the 
important professional features you want in a ter- 
minal, all for under $600.* You get the flexibility you 
need for high-speed data entry, editing, inquiry and 
transaction processing. It's designed to be the back- 
bone of your system with heavy-duty features that 
withstand the rigors of daily use. 
Standard RS-232C interfacing makes the 19 com- 
patible with DEC VT-52 and most computer systems. 
And with the 19, you get the friendly advice and 
expert service that makes Heath/Zenith a strong 
partner for you. 



Sold through Heathkit Electronic Centerst nationwide 
(see your white pages for locations). Stop in today 
for a demonstration of the Heath 19 Smart Video Termi- 
nal. If you can't get to a store, send for the latest 
Heathkit® Catalog. Write Heath Co., Dept. 052-894, 
Benton Harbor, Ml 49022. 



HEATH/ZENITH 



Your strong partner 



Completely ad- 
dressable blinking 
cursor lets you 
edit anywhere on 
screen. 



Reverse video by 
character lets you 
emphasize words, 
phrases or paragraphs. 



High resolution CRT 
gives you sharp, easy- 
to-read image, reduces 
eye-strain. 



Complete ASCII 
character set includ- 
ing uppercase, 
lower case with 
descenders, and 
special graphic 
symbols. 



80 character by 24 
line format, plus 25th 
line for operator mes- 
sages and prompts. 

Professional 
quality keyboard, 
standard type- 
writer layout, 72 
keys, including 
12 special function 
keys. 



Z-80 microprocessor- 
control makes the 19 
capable of multitude of 
high-speed functions. 
It's the only terminal 
with ROM source code 
readily available. 




Insert and delete 
character or line plus 
erase to end of line 
and end of screen 
make the 19 ideal 
for sophisticated 
editors like WORD- 
STAR. 

Cursor and 
special functions 
are accessible 
by keyboard or 
computer, using 
either DEC VT-52 
or ANSI Standard 
protocols. 



Keypad in 
calculator format 
permits fast, 
easy entry of 
numeric data. 



*ln kit form, F.O.B. Benton Harbor, Ml. Also available the completely assembled Zenith Z-19 
at $895. Prices and specifications are subject to change without notice. 



tHeath Company and Veritechnology Electronics 
Corporation are wholly-owned subsidiaries of Zenith 
Radio Corporation. The Heathkit Electronic Centers 
are operated by Veritechnology Electronics Corporation. 



CP-202C 



At A Glance 

Name 

Dual Thermometer Card for the Apple II 

Use 

Long- and short-term temperature measurements 

Manufacturer 

Strawberry Tree Computers 
949 Cascade Drive 
Sunnyvale, CA 94087 

Price 

$260 

Features 

Two temperature-sensing probes, Apple hardware board, software 
contained on a 5/4 -inch disk, user's manual 

Capabilities 

Reads present temperature of each probe, keeps track of maximum 
and minimum of each probe, and records temperature difference 
between probes. Also records date and time when samples are 
taken and sends data to printer or to disk for storage. 

Hardware required 

Apple II Plus with 48K bytes of memory or Apple II having 48K 
bytes of memory with Applesoft; disk drive with DOS 3.2, 3.21, or 
3.3 (will load on 13- or 16-sector machines]. 

Additional options 

Will output with no modifications to almost all printers that have 
been correctly interfaced; will set the date and time directly from a 
Mountain Hardware card; otherwise, the internal clock can be set 
from the keyboard. 



1982 VERSION IFR SIMULATOR 
Apple II Plus DOS 3.3 




Features a lifelike panel that simulates the 
airplane instruments that are used for flying and 
navigating in clouds. FLY IFR LANDINGS, 
PATTERNS, and CROSS COUNTRY in several 
areas of The United States. $50.00 at your 
computer store or direct from: 

PROGRAMMERS SOFTWARE 

2110N.2nd St. 

Cabot Arkansas 72023 

(501) 843-2988 



Hardware 

The thermometer card contains 12 ICs that draw 70 
mA (milliamperes) from the + 5-volt supply and 30 mA 
from the +12-volt supply. If the need arises, up to 7 
cards can be installed in an Apple II, permitting you to 
monitor 14 different temperatures. The probes come with 
10 feet of wire but can be extended to 500 feet without 
loss of accuracy. The probes are electrically isolated from 
their 0.19-inch by 0.65-inch case but cannot be immersed 
in water or other conductive fluids. (Special probes are 
available upon request.) For noncritical applications, the 
probes could be enclosed in a boilable freezer bag. The 
accompanying loss in sensitivity wouldn't affect results 
where slow temperature changes are expected. The accu- 
racy of the unit is 0.4° from -20° to 50 °C and within 1° 
from -50° to -20° and 50° to 100 °C. 

The thermometer card contains two major sections — a 
timer and an analog-to-digital converter. Its data- 
acquisition is similar to that used by the Apple's game 
paddles: resistance changes from the probes are used to 
alter the timing of a latch. The precision of the timing cir- 
cuit is much more accurate, however, than the Apple's 
simple circuit and is fully described in the user's manual. 

Because the system is set up to be slot independent, the 
card can be located anywhere (yes, even slot 0) without 
major modifications. External devices such as fans or 
heaters can be controlled using the data obtained from 
the dual thermometer board with the addition of the nec- 
essary interface hardware. This makes the device helpful 
not only for monitoring temperatures but also for 
controlling them. 

Software 

The software will load on 16- or 13-sector machines 
(DOS 3.3 or 3.2) without modification. When the disk is 
loaded, the time must be set from the keyboard if a 
clock/calendar is not available. This shouldn't be much 
of an inconvenience once the equipment is up and run- 
ning. The internal clock of the dual thermometer is trig- 
gered by the Apple's crystal-controlled clock, so accuracy 
shouldn't be a problem. 

The second thing that must be done upon starting the 
system is to set up the data-measuring parameters. The 
program gives you the ability to: 

• choose one or two probes for temperature measure- 
ment 

• monitor maximum and minimum temperatures of both 
probes 

• set alarms for temperatures above and below the preset 
maximum and minimums 

• record the difference between the two thermometers 

• specify output in Fahrenheit, Celsius, or absolute 
(Kelvin) 

• record data at predefined intervals on a printer or disk 

If the same setup is used frequently, it too can be 
recorded on disk, eliminating the necessity of entering the 
same information each time. 



98 April 1982 © BYTE Publications Inc 



Circle 338 on inquiry card. 



m* 




*# m 




SEATTLE COMPUTER S NEW RAM+ GIVES YOU 
THE MEMORY YOU NEEO AT A PRICE YOU CAN T FORGET. 



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RAM+ is expandable, reliable and is made by Seattle 
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To make your IBM work even better, each RAM + 
card has a RS-232 serial port which uses IBM supplied 
software. And RAM+ comes fully assembled, tested and 
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Circle 366 on inquiry card. 



(la) 



o 

o 

LU 
DC 

D 
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DC 
LU 
Q_ 



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DC 

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on 




* 


* 


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*Lower curve = Probe 
*Upper curve = Mercury 


10 


* 


* * 




















Thermometer 





























* 














* * 


* 


-*• 


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iii. 




Thermometer 



1 2 3 4 5 6 7 8 9 10 11 12 13 14 

TIME (MINUTES) 
(lb) 

90 
80 
70 
60 
50 
40 
30 
20 
10 

1 2 3 4 5 6 7 8 9 10 11 12 13 14 
TIME (MINUTES) 

Figure liTracking Strawberry Tree's thermometer probe versus 
a laboratory mercury thermometer. Figure la shows responses 
to an 8. 89° C/ minute rate of change; figure lb shows responses 
to a 4.57°C/minute rate of change. 

One missing feature, however, is a method for obtain- 
ing an average temperature for the collected data. If 
desired, the software can be modified to accumulate the 
sum of all temperature samples taken and divide that sum 
by the total number of samples. This should be an easy 
modification since the disk is not "copy protected," and 
the software is fully described in the user's manual. 

Limitations 

One of the major limitations of the Strawberry Tree 
Dual Thermometer card is the stabilizing time necessary 
for accurate measurements. The manual states that the 
probe requires 4 minutes to stabilize to within 0.1° for a 
100° change. For comparison, a laboratory-grade mer- 
cury bulb thermometer will stabilize over the same 
temperature change in approximately 10 seconds. This 
would limit application of the device where large 
temperature variations can occur in relatively short time 
intervals. 

Appendix E of the user's manual addresses this issue 
and offers several suggestions for obtaining greater accu- 



racy. Figure 1 shows two experimental plots. Each plot 
contains two curves, one of the probe and one of a mer- 
cury bulb thermometer. In figure la, the average rate of 
change is 8.89 °C per minute, while that of figure lb is 
4.57°C per minute. The rapid change in temperature with 
respect to time in figure la produces as much as a 4° error 
between probe and mercury thermometer. When the rate 
of change is slowed by a factor of 2, the two devices give 
about the same reading. This drawback won't be a prob- 
lem where temperature variations change slowly. In- 
deed, given the required stabilization time, I found the 
probes to be well within their rated accuracy. 

Applications 

The possible applications of this dual thermometer 
board are many because of the careful attention given to 
writing the software. With the ability to record data on a 
printer or disk, many long-term temperature studies can 
be undertaken. 

An engineer could use the dual-thermometer board in a 
solar heating experiment. One thermometer probe would 
monitor the internal temperature of the solar collector 
while the other would record the surrounding 
temperature. The data collected would help determine 
the best angle for the collector, the best collector coating 
for maximum heat gain, etc. With the card, readings for 
an entire day could be gathered automatically. 

A homeowner might want to do a long-term energy 
study by monitoring the temperature difference between 
the inside and outside of the house. After keeping track of 
temperature differences and the amount of oil, gas, or 
electricity used per month, the most efficient temperature 
setting for the house could be determined by plotting a 
curve of temperature difference versus fuel consumption. 

A scientist desiring to monitor the temperature of a 
microscopic culture might wish to record the information 
on a printer as it is gathered. A further possibility would 
be to have the computer sound an alarm if the culture got 
too hot or cold (this could be done by setting the alarms 
for the probe at the maximum and minimum limits). 

Conclusions 

The hardware and software of the Strawberry Tree 
Dual Thermometer board are excellent, with all opera- 
tions fully supported and documented. Any modifica- 
tions to the BASIC program should be straightforward 
and require only fundamental programming skills. 

The temperature probes can be located at distances up 
to 500 feet, offering great flexibility in probe placement. 
Special probes can be ordered for immersion in liquids. 
Two probes can be used at the same time, each recording 
its present temperature, maximum, minimum, and the 
temperature difference between the two. 

The software permits readings to be calibrated in 
Fahrenheit, Celsius, or Kelvin. Data can be recorded on a 
printer or disk at preset intervals. An alarm can be set for 
each probe to indicate when a preset maximum or 
minimum temperature has been passed. ■ 



100 April 1982 © BYTE Publications Inc 



SUPERFILE 

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Circle 182 on inquiry card. 



Book Reviews 



Software 
Psychology: 
Human Factors In 
Computer and 
Information 
Systems 

Ben Shneiderman 
Winthrop Publishers Inc. 
Cambridge, MA, 1980 
320 pages, hardcover 
$24.95 



Reviewed by 
Bruce Robert Evans 
16 Marwin Road 
Pickering Ontario 
Canada L1V2N7 



Until recently, computers 
have been the domain of pro- 
fessionals. With the advent of 
personal computers, informa- 
tion networks, and dedicated 
controllers in equipment, 
programmers and designers 
must be aware of the impact 
of software on end users and 
vice versa. Much has been 
written about human engin- 
eering, but nothing has ap- 



peared about humanizing 
software. Software Psy- 
chology will help the systems 
engineer and programmer 
remedy this deficiency. 

The layout of the book re- 
flects the author's back- 
ground in the psychology of 
learning. At the beginning of 
each chapter, there is a list of 
the section headings, fol- 
lowed by an explanation of 
what is to come. Two sum- 
maries, one of practical points 
for the programmer and one 
of possible leads for the 
psychology researcher, follow 
the body of the book. The 
repetition distressed me, but 
with time it became obvious 
that it was achieving the 
desired purpose — I was re- 
taining the material. 

Shneiderman starts by 
analyzing what programmers 
do. Using one of the key 
tenets of management 
analysis, he delineates tasks 
and their performance. With- 
out generalizing, the author 
dissects some of the well- 
entrenched "truths." Do com- 
ments clarify a program? Do 
symbolic variable names 
help? Expect your prejudices 



to be challenged. The author 
insists on measuring as he at- 
tempts to assess a program- 
mer's output. Many com- 
monly held beliefs topple. For 
example, while the number of 
lines produced may be accept- 
able criterion for one pro- 
gram, the efficiency of style 
may be better in another. 

Chapters seven and eight, 
in which Shneiderman dis- 
cusses database systems, 
should be read by all pro- 
grammers. In them, the 
author explores possible 
sources of friction between 
programmers and nonprofes- 
sional users. Ways of dealing 
with irate nonprofessional 
users (Why is my credit card 
bill different from what I 
think it should be?) are dis- 
cussed. 

In chapter nine, Shneider- 
man discusses programming 
languages, emphasizing the at- 
tempts to create new lan- 
guages that will correct some 
of the faults of existing ones. 
(Does a month go by when 
someone doesn't come up 
with the "perfect language"?) 
The author stresses that 
because no one language 



covers all situations, pro- 
grammers should consider 
the advantages and disad- 
vantages of each when writ- 
ing for a nonprofessional. 

Chapter ten, "Interactive 
Interface Issues," justifies the 
entire book. In it, Shneider- 
man indicates the need for 
more study of the psycho- 
logic impact of computer pro- 
gramming on the end user. 
He discusses computer sys- 
tems from the user's point of 
view and points out user 
demands of which the pro- 
grammer may be completely 
unaware. 

In summary, Ben Shneider- 
man guides the systems 
engineer in deciding what a 
customer wants and needs, 
suggests how the software 
should be written, and assists 
in its evaluation. At the same 
time, the author shows the 
programmer what the soft- 
ware user wants and how the 
end user looks at a computer 
system. Often the user is very 
different psychologically and 
intellectually from the pro- 
grammer; the successful pro- 
grammer must be aware of 
this. ■ 



The Graphics Family. 

the most versatile, easiest-to-use 
graphics available for your Apple II. 



The A2-3D1/3D2 with A2-GE1 Graphics Editor package lets you 
put simultaneous multiple images on your screen . . . where you 
want, in the size you want, in your choice of orientation, complete 
with upper and lower case text. Because the most important part 
of your computer system is you. $119.85 



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"Apple" is the registered trademark of j 






102 April 1982 © BYTE Publications Inc 



Circle 390 on inquiry card. 



Start talking 
business 




with your Apple 



COBOL is the most effective business language. 
Apple II is the most friendly business computer, 
CIS COBOL with FORMS-2 brings together the 
best features of COBOL and Apple to enable you to 
deliver the most effective, user-friendly applications, 

Business Programmers: Take the COBOL 
expertise you have acquired on big business 
mainframes, and use it on Apple II to create friendly 
applications that will talk directly to your users - 
where it suits them best, on their own desks, 

CIS COBOL's dynamic module loading gives 
you big application capability and the FORMS-2 
source generator lets you build and modify 
conversational programs from visual screen 
formats, creating much of the code automatically. 

Application vendors: CIS COBOL with 
FORMS-2 steps up the pace for your development 
of the high quality professional application 
packages needed today, And creating them in 
COBOL makes them more maintainable. 



Over half the Apple ll's now being sold are going 
to business or professional users so demand for 
quality applications is growing fast creating big 
business opportunities for you. 

Stability proven b y the U S Government. 

CIS COBOL has been tested and approved for two 
consecutive years by the US General Services 
Administration as conforming to the ANSI 74 
COBOL Standard. Apple II under CP/M is included 
in CIS COBOL's 1 98 1 GSA Certificate of Validation 
(at Low-Intermediate Federal Standard plus 
Indexed l-O and Level 2 Inter-Program 
Communication). 

Get your hands on CIS COBOL at your 
Apple dealer. 

Talk business with him now! 

Micro Focus Inc., 1601 Civic Center Drive 
Santa Clara, CA 95050. Phone: (408) 248-3982. 



MICRO FOCUS 



CIS COBOL with FORMS-2 for use on the Apple II with CP/M is an Apple Distributed Product. 
CIS COBOL and FORMS-2 are trademarks of Micro Focus. CP/M is a trademark of Digital 
Research. Apple II Is a trademark of Apple Computer. 



Circle 264 on inquiry card. 










«*•» 



.M ex 




ALL IT 
NEEDS IS THE 
PERSONAL COMPUTER 
CONNECTION 
FROM 
NETWORK 
DATA 
SYSTEMS. 

This printed circuit, 
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• User-selectible baud rates 

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• Four parity options 

• Full or half duplex modes 

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DEALER INQUIRIES INVITED 



Product Description 



The Epson HX-20 

The First BYTE-sized Computer 



104 April 1982 © BYTE Publications Inc 



Circle 298 on inquiry card. 



Gregg Williams 
Senior Editor 



Unfortunately, no monthly magazine can be complete- 
ly up to date on a given subject — some new product or 
idea always appears between the time we send the 
magazine to the printer and the day you see that same 
issue. However, we did get a chance to preview a product 
so exciting that we "stopped the presses" to get it into this 
issue. 

The Epson HX-20 microcomputer (see photo 1) is a 
remarkable unit that might be dubbed the first "notebook 
computer" — larger than a pocket computer and smaller 
than a briefcase computer, it is about the size of a 
notebook. It weighs in at 1.73 kilograms (3 pounds, 13 
ounces) and measures 28.9 by 21.6 by 4.44 centimeters 
(11.375 by 8.5 by 1.75. inches)— somewhat lighter than 
but almost the same size as two issues of BYTE. The 
HX-20 has a full version of Microsoft BASIC, 16K bytes 
of memory, a standard-size and standard-configuration 
keyboard, a 24-character-per-line printer, a built-in 
cassette interface, and a 20-character by 4-line liquid- 
crystal display. The product will be officially announced 
at the National Computer Conference in June. Epson 
plans to have its distributors fully stocked with HX-20s 
by the time it is officially introduced. 

The unit was lent to us for a few days by Chris 
Rutkowski of Epson America Inc. Since this was a sneak 
preview or the HX-20, Chris told us some but not much 
about it. Most of the details below are a result of our 
physical inspection of the unit. For example, executing 
the BASIC statement "PRINT FRE(X)" produces the 
answer 12,832. This leads me to believe that the unit has 
16K bytes of RAM (random-access read/write memory), 

Circle 239 on inquiry card. » 



Appje Logo 

* • 

has arrived 



* 4 



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the sophisticated yet simple to use language 
yon have been reading about 
is now available for your Apple //.\ 
" Contact yoyr Apple dearer today. 



222 Brunswick Blvd. 

Pointe Claire, Que. 

Canada 

(514) 694-2885 



©Registered Trademark, Apple Computer inc. 



cgmputi 

systems inc. 



989 Avenue of the Americas 

New York, N.Y. * 

U.S.A. 

(212) 564-6020 



Product Description. 




Photo 1: A prototype of the HX-20 microcomputer. The final 
unit will have a different keyboard layout. 




Photo 2: The HX-20 printer and a printout of its character set. 
The Japanese katakana characters will be replaced in the U.S. 
version of the unit by geometric symbols that can be combined 
to make larger graphic images. 




Photo 3: The liquid-crystal display of the HX-20, which gives 
four rows of 20 characters each. 



12,832 of which are free for BASIC programs and data. 

The unit we saw is a prototype of the final unit, which 
may be packaged somewhat differently and which will 
have a typewriter-style keyboard layout. Aside from the 
layout, the present keyboard is very good— it is stan- 
dard-sized (a very important feature if the computer is 
used for programming, word processing, data entry, or 
similar applications) and the keys have a good feel. The 
printer can display 24 characters per line, each in a 5 by 7 
dot matrix (see photo 2). The LCD (liquid-crystal dis- 
play) provides four rows of 20 characters, each displayed 
within a 6 by 8 dot matrix (see photo 3). Both the printer 
and the LCD can show graphics, numbers, punctuation, 
and uppercase and lowercase letters. The LCD is 
ultimately 120 dots by 32 dots, each of which can be con- 
trolled by BASIC. Because Epson is a subsidiary of Seiko 
(the watchmakers), you might suspect the HX-20 to con- 
tain a clock; it does. The clock is accessed from BASIC by 
reading the variable TIME$. Setting the clock is just as 
easy. 

The cassette interface is said to transfer information at 
about 2400 bits per second (about 300 bytes per second) 
onto a standard dictating machine microcassette. This 
area of the unit appears to be detachable, which may in- 
dicate other storage options and/ or telecommunication 
potential. 

The unit has several interesting sockets. The rear of the 
unit contains a socket for a power supply (the unit is 
estimated to run 50 to 100 hours on the internal nicad 
batteries), as well as two DIN sockets marked SERIAL 
(with holes for five pins) and RS-232C (with holes for 
seven pins). The left side contains a long, narrow, re- 
cessed plug containing two rows of 20 pins each (perhaps 
a system bus of some kind), and the right side contains 
plugs for an external cassette recorder, as well as a small 
phono jack marked BARCODE (which means that the 
unit is capable of reading bar codes). In addition, the 
right side of the unit contains a recessed Reset key and an 
on-off switch. (The unit, however, is never really "off"; 
this switch turns off the LCD display, but retains the pro- 
gram currently in memory.) 

Few details on the internal organization of the machine 
are yet available. It contains CMOS (complementary 
metal-oxide semiconductor) memory to keep the power 
consumption low. The HX-20 also uses the 6301 
microprocessor, a CMOS version of the Motorola 6801 
microprocessor. 

The price? Epson hadn't decided at the time this was 
written, but I was led to believe that it would be under 
$1000. 

I hope you are as tantalized by this information as I 
am. More information will be available after the unit is 
introduced at the NCC in June. Until then, it is enough to 
know that microcomputers are becoming more portable, 
more powerful, and cheaper at the same time, a trend 
that will probably not stop with the HX-20. ■ 



106 April 1982 © BYTE Publications Inc 



▲ 



A 




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IBM Personal Computer • Xerox 820 

Apple • SuperBrain • Heath-Zenith 

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Suggested list for 5 mb: Targa 20 

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6.38 Mbytes unfor- 
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Our Targa Winchester-type, 
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in desk-top dimensions of 
15" x 5 1 /4" x 13V 2 ". It 
comes complete with ca- 
bles, software and interface. 
Call or write for complete 
specifications and/or the 
dealer nearest you. Dealer 
inquiries invited. 

Circle 86 on inquiry card. 



CMC INTERNATIONAL 

A Division of Computer Marketing Corporation 
11058 Main • Suite 220 • Bellevue, WA 98004 • Phone (206) 453-9777 • Telex: 152556 SEATAC 

Call Toil-Free 1-800-426-2963 



A Human-Factors Style Guide 
for Program Design 

Taking the user into account in the design of software. 



Henry Simpson 

Anacapa Sciences Inc. 

P.O. Drawer Q 

Santa Barbara, CA 93102 



Human factors is a small but grow- 
ing discipline which seeks to provide 
a method for taking into account 
human strengths and limitations 
during the design of computer hard- 
ware and software. In this article, I'll 
present a brief introduction to human 
factors and discuss its application to 
program design. I'll define six human- 
factors design principles and show 
how they can be applied to three 
areas of program design: data entry, 
display-screen design, and sequence 
control. 

Human factors can be applied to 
any area in which a human being in- 
teracts with a machine. The discipline 
applies, or at least can and should be 
applied, to many aspects of man's in- 
teraction with computers. The most 
obvious area, and the one most 
people think of. when considering 
human factors, is hardware design. 
Human-factors specialists often 
design video displays and controls. 

More recently, human factors has 
been applied to software design. Re- 
search has led to the development of 
human-factors guidelines that pro- 
grammers can use to make their pro- 
grams easier to use and less prone to 
error. Human factors is also impor- 
tant to the design of computer operat- 
ing systems, programming languages, 
and documentation, although the 
discipline has received less attention 
in those areas. 



Human factors matter because peo- 
ple must operate machines. If you fail 
to take people into account during de- 
sign, then your machine (or system or 
program) may be difficult or impossi- 
ble for people to operate. As obvious 
as it seems, this point is often over- 
looked. Consider some recent ex- 
amples. No brand names are men- 
tioned in what follows, but you may 
recognize some of the players: 

• The microcomputer whose non- 
standard keyboard made it awkward 
for touch-typists — all keys were 
there, but they were the wrong kind 
of keys and in the wrong locations. 



The more serious the 

error consequences, the 

more designers should 

consider human 

factors. 



(The keyboard has since been rede- 
signed.) 

• The minicomputer whose operat- 
ing system identifies program errors 
with numeric codes that are con- 
tained in three separate manuals. 
(This machine was recently discon- 
tinued.) 

• The computer program whose 



screen displays are cluttered and con- 
fusing, whose data-entry sequences 
permit input errors that cause the 
program to interrupt, whose menus 
can lead the operator down blind 
alleys and into stable program states 
from which he or she cannot escape. 
The documentation for this program 
consists of three smudged photo- 
copies of an original that displays 
creative spelling and grammar and 
omits many important details. 

We often blame human error for 
disasters and near disasters, from 
nuclear near-meltdowns to bank 
errors in checking account balances. 
Equally often, we blame "the com- 
puter" for some ill fate that befalls us. 
Seldom do we recognize that neither 
man nor machine alone is completely 
responsible. In today's complex 
world, man and machine work to- 
gether interactively. The "system" is 
the combination of both. 

When we design things, it is usually 
fairly easy for us technically oriented 
people to take into account the limita- 
tions of our hardware. However, we 
are likely to forget that the operator 
or maintainer of our system has 
limitations. We can design much 
better systems — more workable and 
more maintainable — if we accurately 
take human limitations into account. 

What are human limitations? First 
and most obvious, no two human be- 



108 April 1982 © BYTE Publications Inc 



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150 Characters Per Second 

136 Columns Per Line 



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For more information 
call your local distributor: 

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ARIZONA 

The Phoenix Group Inc. (602) 

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Basic Systems Corp. (213) 

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ILLINOIS 

Electro-Tech Marketing Assoc. (312) 

Engineered Sales (312) 

INDIANA 

Audio Specialists (219) 

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Circle 342 on inquiry card. 




MINNESOTA 

663-0375 Integrated Peripherals 

Vikeland Sales 
967-1421 MISSOURI 

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673-4300 NEW YORK 

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ings are alike. They vary in size, 
strength, acuity, intelligence, educa- 
tion, and level of motivation. The 
general requirement for considering 
human factors in the design of your 
system, whether hardware or soft- 
ware, is to recognize the needs of the 
users. The type of user varies with the 
application. If you are designing an 
arcade game with a coin slot and two 
push buttons, you are aiming at a dif- 
ferent sector of the population than if 
you are developing a computer-based 
econometric model to predict the 
gross national product in 1985. Either 
of those programs can be written for 
specific, definable, homogeneous 
groups of users. 

More often than not, however, the 
hardware or software we design will 
be used by a varied group that ranges 
widely in sophistication. Knowing 
your system users and recognizing 
their needs are the first two steps in 
taking human factors into considera- 
tion during system design. 

In general, the rules for designing a 
system with the user in mind parallel 



those for good writing: define your 
system users, know their limitations, 
and find the simplest way to get your 
message across. 

That which separates good pro- 
grams from bad cannot always be 
described in terms of simple, obvious 
things such as bad keyboard designs 
or cumbersome error-handling proce- 
dures. I can name some general 
qualities to look for, however. First, 
programs that consider human fac- 
tors are generally easier to learn and 
use than those that do not. They 
usually have simpler displays, are less 
likely to "bomb/' and are supported 
by good user documentation; they 
appear to be written for less special- 
ized users and not for computer ex- 
perts. These programs also refrain 
from trying to make the machine 
behave as if it were a human being. 
Poorly designed programs lack some 
or all of these features. 

To illustrate when human factors 
matter I'll limit my discussion to soft- 
ware design and, more specifically, to 
microcomputer software in which the 



operator controls the computer and 
interacts continuously with it. This 
scope includes such applications as 
games, business and scientific pro- 
grams, computer graphics, and com- 
puter music but excludes most con- 
trol, robotics, and other minimally 
interactive applications. 

A human-factors purist might say 
that serious consideration of human 
factors always matters, but this 
simply isn't true. You can decide in 
each case how important human fac- 
tors are by looking at four different 
aspects of your program: (1) number 
of people who will operate the pro- 
gram, (2) diversity of the operators' 
backgrounds, (3) complexity of the 
program, and (4) consequences of 
operator error. 

Obviously, the more people who 
will operate your program, the more 
time and energy you will invest in its 
development. If you are running a 
business, you want to assure that 
your A/R (accounts receivable) pro- 
gram works efficiently and effectively 
because it will cost you money and 



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The GRQ Series Interface features: 

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3. Fifty thru 9600 Baud data rate options. 

4. Two K buffer; supports X-on, X-off protocol as 
well as RTS signals. 

110 April 1982 © BYTE Publications Inc 



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You can "set it and forget it" for the ulti- 
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perhaps your credit rating if it 
doesn't. 

If that same program must serve a 
wide group — ranging, say, from clerk 
to company president — then you 
must assure that the program serves 
all levels well. This takes special 
effort during program design. 

The more complex the program, 
the greater the chance of error, and 
the more you must strive to reduce 
the likelihood of error by carefully 
considering human factors. 

Last, and probably most impor- 
tant, are error consequences. The 
more serious these are, the more im- 
portant the human element becomes. 
If the reactor core will melt down, the 
navigator will get lost, or the names 
and addresses of all the people who 
owe you money will disappear, then 
the consequences of error are very 
serious indeed. If the worst that can 
happen is that the bouncing ball in 
your game program may disappear 
from the screen, then the conse- 



quences are not quite so serious 
(unless you depend upon the program 
for your livelihood). 

In sum, if you are writing programs 
purely for your own use and are not 
tracking important data, then you 
have probably spent too much time 
on this article already. On the other 
hand, if you are writing programs for 
a wide and varied group of users to 
track things that matter to them, then 
human-factors considerations are im- 
portant. 

Design Principles 

If you decide to apply human fac- 
tors to your program design, where 
do you begin? Probably the best way 
is to familiarize yourself with some 
general human-factors design princi- 
ples. Six such principles are presented 
below. These principles grow out of 
behavioral research conducted over 
the last several decades, although 
their application to program design is 
recent. Later in this article I'll give 




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specific examples of how these prin- 
ciples may be applied. 

Provide Feedback: People need to 
know that an action they have taken 
has had an effect. When you turn the 
wheel of your automobile, you re- 
ceive feedback in the form of 
resistance from the wheel, centrifugal 
force on your body, and movement 
of your visual field. In turn, you 
adjust the rate at which you turn the 
wheel to conform to the feedback you 
are receiving. Without this feedback, 
you would find it much more difficult 
to control your automobile. 

The user of your program also 
needs feedback. If he makes a key- 
board entry and nothing appears on 
the screen, then he has no way of 
knowing that his action has had an 
effect. In consequence, he may repeat 
his action or try another, possibly 
causing something unintended to 
happen. 

Feedback should be immediate and 
obvious. Show it on the screen in a 
place where it is expected. 

Be Consistent: Mention "consisten- 
cy" in a group and someone will 
probably quote Emerson to the effect 
that it is the "hobgoblin of little 
minds." Emerson may have been able 
to get along without it in certain 
trivial matters, but computer pro- 
grammers cannot. The tools and pro- 
gramming languages with which they 
work are based on rigid adherence to 
rules of syntax, the order of program- 
ming operations, and the laws of 
mathematics. Rigid adherence to 
these "laws of the machine," which 
are internally consistent, reduces un- 
certainties and makes it possible to 
program the machine exactly. Human 
beings can tolerate more ambiguity 
than machines, but ambiguity re- 
duces people's effectiveness. If we 
paid half as much attention to con- 
sistency in our programs' interactions 
with human beings as we do in the in- 
teractions between programs and 
machines, most of our programs 
would be improved. 

What, exactly, do we mean by 
"consistency"? One way of defining it 
is as a set of rules that you, the pro- 
grammer, establish for yourself and 
follow compulsively. These rules per- 



112 April 1982 © BYTE Publications Inc 



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mit the operator to learn one part of 
your program's operation and then to 
apply the new knowledge to other 
parts of the program. For example, 
you might make a rule that all of your 
error messages will appear on the bot- 
tom line of the display screen. When 
the operator sees one error message 
displayed on the bottom line, he ex- 
pects all others to be displayed there, 
too. If they are, then the rule is ad- 
hered to, and the operator will not 
have to learn a new rule for each new 
display. If not, then the operator's 
learning task is that much more dif- 
ficult. 

Minimize Human Memory 
Demands: Psychologists have deter- 
mined that human beings possess two 
types of memory — short-term and 
long-term. A vast amount of research 
has been conducted on the subject, 
most of which will interest only the 
specialist. About human memory, the 
computer programmer needs to 
recognize two things. The first of 



these is obvious, the second less so. 

First, computers have better memo- 
ries than people. (We said it was 
obvious.) Data stored on magnetic 
media are never forgotten. 

Second, computers always remem- 
ber things exactly as they were 
stored. People usually do, but some- 
times they get things mixed up. 

What follows from these two 
points is that, when designing pro- 
grams, you should rely on computer 
memory as much as possible. Sup- 
pose, for example, that your program 
has many subprograms. How should 
the operator select a subprogram — 
from a displayed menu or by entering 
a memorized mnemonic? Although 
selection with memorized mnemonics 
(used in "program-like languages") 
has advantages in some situations, 
the displayed menu depends much 
less on operator memory and is 
generally preferable. (Some players 
of Star Trek games may recall the 
frustration with which they 




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attempted to master the game in the 
absence of displayed menu options.) 

Keep the Program Simple: 
Simplicity in programming, as in 
writing, does not come easily or pain- 
lessly. You must work to achieve 
even the appearance of simplicity. 
Simplicity usually results from paring 
down or editing. In programming, as 
in writing, simplicity is an ideal that 
one strives to achieve by conscious 
design, by trial and modification, by 
cutting away the unnecessary, and by 
reorganizing and rearranging. 

Match the Program to the 
Operator's Skill Level: You must 
determine the operator's skill level 
before you write your program. 
Determine also if operators of differ- 
ing skill levels will use the same pro- 
gram. Human-factors specialists do 
these two things systematically by 
conducting a task analysis. There are 
several ways to do this, but usually it 
involves defining what mission a 
system must perform, what functions 
are involved in this mission, and 
what tasks are required to accomplish 
the functions. Conducting task 
analyses is time-consuming, tech- 
nical, expensive, and probably 
beyond your needs or interests. Still, 
you do need to think about operator 
tasks as you write your program and 
ask questions like the following: 

• What will operators be expected to 
do? 

• What decisions must they make? 

• What must they know to make the 
decisions? 

• What skill levels will be required? 

Consider these questions before you 
write your program. Then design 
your program so that it matches the 
skill level of your system users. 

Sustain Operator Orientation: If 
you have ever been lost then you 
know what not being oriented is. 
Anyone who has ever used a com- 
puter has had the experience of get- 
ting into some new program and not 
being able to find the way out. This 
often happens when you try the pro- 
gram without first reading the 
manual (as all of us are prone to do). 

You have an obligation as a pro- 



114 April 1982 © BYTE Publications Inc 



Circle 38 on Inquiry card. 



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BYTE April 1982 115 



DATA COLLECTION FORM 
Doily Man-hour Availability 
1. Date j. / 



MAN-HOURS 
Available Direct Overtime 



DATA ENTRY SCREEN 
Doily Man-hour Availability 
| Dote (Month/Day/Year) 

MAN-HOURS 
NAMES Avail. (0-12.0) Direct (0-12.0) Over. (0-4.0) 



2- I 

3. ( 

4. I 



Figure 1: A data-collection form and the data-entry screen that goes with it. The data- 
entry screen resembles the form. Prompts shown in parentheses on the screen make 
clear the expected data formats and give range limits. The brackets serve as field 
delimiters, showing the maximum length allowed for each entry. 



grammer to minimize the possibility 
of disorientation. Provide your 
operator with signposts that tell him 
where he is and how to get back to 
where he came from. Menu-driven 
programs often do this by providing a 
main menu which serves as a home 
base. The program begins with this 
menu from which the operator can 
select various subprograms, perform 
them, and then return. 

Some game programs are inten- 
tional mazes, consciously designed to 
disorient the operator. If that's your 
intention, all well and good. But if it's 
not, remember that an unwanted 
maze is about as much fun as an inac- 
curate road map on a dark and rainy 
night. 



The six principles described above 
reduce to one idea: know the needs of 
your system users. Recognize that 
they need feedback to avoid confu- 
sion, consistency to ease the learning 
process, minimal strain on memory 
capacity, simplicity rather than com- 
plexity, demands gauged to their skill 
levels, and constant, clear orienta- 
tion. 

The remainder of this article will 
focus on three areas of computer pro- 
gramming: data entry, display-screen 
design, and sequence control. Data 
entry concerns how you get data into 
a database; display-screen design 
concerns layout of video-terminal- 
display screens; and sequence control 
concerns how you interact with your 



program to get it to do something. 

I'll show how the six human-factors 
principles apply in each of these 
areas. In most cases, recommenda- 
tions made are based on research that 
has shown that the suggested feature 
permits more effective man-machine 
interaction. In a few cases, recom- 
mendations are based on prevailing 
practice. None of these guidelines 
should be applied blindly, and all of 
us will find it necessary to ignore 
them from time to time. But most of 
these are simple things to do, and if 
you follow them, you will write a 
better program. 

Data Entry 

The following guidelines apply 
mainly to programs in which data are 
entered through the keyboard to 
build a database which the program 
accesses later. Typically, the data 
entry process consists of the follow- 
ing sequence of steps: 

• presentation of a prompt 

• data entry by the operator 

• display of entered data on the 
screen 

• error test 

• presentation of an error message if 
entered data fail error test 

• editing of data 

• acceptance of data into database 

Prompting: If data are to be 
entered into the computer from a 
standardized data-entry form, then 
the data-entry screen should resemble 
that form as closely as possible. The 
cursor should move from field to field 
as the operator fills in the form. It is 
easier to write a program consisting 
of a series of INPUT statements that 
cause the screen to scroll. However, 
the operator can more readily orient 
himself to a screen that looks like a 
data-entry form. Figure- 1 shows a 
data-collection form and a data-entry 
screen designed to elicit the necessary 
data. The screen presents prompts, 
states acceptable ranges, and delimits 
fields. 

The program should provide a 
prompt for every data input. The 
prompt should be brief and specific, 
and show the range limits and entry 



116 April 1982 © BYTE Publications Inc 



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2/31/1979 } Date ( Month/Day/Year} 



DATA ENTRY ERROR: Date contains invalid DAY -- re-enter date 



Figure 2: A sample error message. The message is specific and helps the operator 
correct the error identified. 



format of data to be entered. Range 
limits or entry format can be shown 
parenthetically after the prompt. For 
example, a date entered in the form of 
month-day-year could be prompted 
as follows: "Enter Date (Month/ 
Day/Year)/' If there is a length limit, 
then this length should be shown on 
the screen using an underline, pair of 
brackets, or other visual cue. If cer- 
tain data entries have default values 
(i.e., values that the computer will 
assign unless the operator enters 
others), then display the default 
values — do not rely on operator 
memory. If there are similar or iden- 
tical data-entry requirements in dif- 
ferent parts of the program, prompt 
consistently. One way to do this is to 
put data-entry statements into sub- 
routines that can be called from 
various parts of the program. 

Entering Data: You do not always 
control the length of the data to be 
entered, but when you do, keep 
length to a minimum. This saves key- 
strokes and time and reduces errors. 
Provide feedback by displaying 
entered data on the screen. If data be- 
ing entered consist of logically related 
groups, then permit the user to enter 
several fields together, rather than re- 
quiring him to enter each item sepa- 
rately. 

Error Check: Check all entered 
data for errors. The types of checks 
you must make depend upon the data 
and what will be done with them. An- 



ticipate possible errors, check for 
them, and protect against them. For 
example, if the entry is supposed to 
be a number, anticipate what will 
happen when (not if) the operator 
enters a letter. Many programmers 
protect against this by taking all in- 
puts as character strings and then 
converting them to equivalent numer- 
ic values. 

Analyze the situation and be ready 
for errors. Are there range or length 
limits to what is acceptable? Is it 
possible for the operator to enter 
something that will cause an illegal 
program action to take place — for ex- 
ample, dividing by zero or attempting 
to take a substring of illegal length? 

When an entry error is detected, 
alert the operator, identify the error, 
and tell him how to recover. In other 
words: alert, identify, direct. Alerting 
signals must differ from the custom- 
ary background. An audio tone — a 
beep — is alerting but meaningless if 
the program is already emitting a 
continuous stream of beeps. Similar- 
ly, a flashing message can effectively 
alert, provided that the screen is not 
filled with other flashing messages. 
Many programmers reserve the use of 
both sound and flashing messages for 
those conditions that truly require an 
alert. 

The error message itself should be 
placed consistently from screen to 
screen. Ideally, it should appear near 
the erroneous entry. The content of 



the message must tell what is wrong — 
for example, that the entered value is 
too long. If error identification will 
permit the operator to figure out 
what to do next, then that is a]] the 
message needs to contain. However, 
if many possible actions may be 
taken, then the message must also tell 
the operator which to take. If 
prompts to the user are adequate, 
then it should be possible in most 
cases for the operator to figure out 
what corrective action to take based 
solely on definition of the error. 
Figure 2 shows a helpful error 
message. 

Editing: Editing is an important 
part of the data-entry process, and no 
data-entry program is complete with- 
out editing capability. Being human, 
operators will make data-entry errors 
that they may not recognize until 
later. You should therefore permit 
them to edit entries before the pro- 
gram accepts data into a database. 
Many programs permit data to be 
edited at three stages: during initial 
data entry (while being typed in), 
after a block of related entries has 
been made, and after the data have 
become part of the database. 

The first editing capability is rou- 
tine and in fact most people probably 
do not think of this as editing. If you 
make a typing error, you can usually 
back up the cursor before data are 
stored. The last capability, editing the 
actual database, varies in impor- 
tance, but in many programs with 
large databases it is considered as 
necessary as utility programs for 
copying files, purging files, or the 
main menu itself. 

Less routine, often ignored, yet 
very important is the block editing 
capability mentioned above. Often 
the program user will not recognize 
an error until after he has made 
several data entries. IF he cannot go 
back and correct the error at that 
point, it may be uncorrectable, or he 
may have to use a separate database 
editing program to make the correc- 
tion. The way block editing typically 
works is that after the operator has 
made a set of related entries, the 
screen presents a prompt asking if he 
wants to edit any earlier entries. If he 



118 April 1982 © BYTE Publications Inc 



"My computer helped me write 

The Final Encyclopedia. I wouldn't trust 

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Science Fiction Author, 
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Scotch 8" and 5 1 /t" diskettes are 
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* * WARNING * * 



You hove selected the 'PURGE FILES' program. 
If you use it, your dota files will be purged. 

Do you want to continue with the PURGE program? 
{ Y/N U 



Figure 3: A message that protects the operator against a serious error. The operator 
must confirm the decision to purge the data files before the program will proceed. 



indicates that he does, the program 
asks him to define the entry he wants 
to correct, usually by line number. 
Then the cursor moves to the appro- 
priate data-input field to permit re- 
entry of data, and the edit prompt re- 
appears to permit corrections. When 
the operator indicates that he has no 
more changes to make, the program 
moves on to the next step. 

Certain data entries have far- 
reaching effects. A "profound, irre- 
versible data entry" is one that will 
significantly affect the database or a 
phase of program operation. How 
profound the data entry is depends, 
of course, on the situation. Conse- 
quences of data-entry errors in these 
cases vary from inconvenience (you 
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six months' worth of data). 

Clearly, it is important to protect 
the operator from such traps by pro- 
viding "fail-safe" devices. The general 
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more complex than for usual data en- 
try. One way is to make data entry 
require two stages. For example, 
when the operator selects the "FIRE 
ICBM" program from the menu, fir- 
ing does not occur immediately but 
causes a message to appear on the 
screen that tells what will happen 
next. This is accompanied by a 
prompt that permits the operator 
either to continue or to back out. 

Protect your operator against him- 
self. The programmer who writes a 
program that will purge all files at the 
stroke of a single key deserves no 



mercy and will receive none from 
program users. Figure 3 shows a 
message that provides sufficient 
warning to the operator before begin- 
ning to purge data. 

Display Screen Design 

Screen layout design is partly art 
and partly science but all program- 
mers can profit by observing the 
guidelines in this section. 

Designing a good screen requires 
planning. Many experienced pro- 
grammers find that a screen design 
aid, consisting of a paper matrix that 
identifies all possible character loca- 
tions on the screen, is useful. This 
permits design of the screen with 
paper and pencil. The design can be 
perfected before it is committed to 
code. (It is much faster to make pencil 
erasures than to change a series of tab 
settings.) 

As a general rule, access screens by 
paging, not by scrolling. Keep in 
mind that people find it easier to read 
stationary pages than moving pages. 
The only people who like to read 
scrolling information are those at the 
end of hot news wires. Unless your 
program has that sort of application, 
clear the screen before you put up a 
new display. 

Most displays need a title to tell the 
operator what he is looking at. The 
title should be centered at the top of 
the screen. 

Display screen designers center dis- 
played information primarily for 
aesthetic considerations, although 
centering assumes more practical im- 



portance with large screen displays. 
With large screens, if information is 
not centered, the operator will spend 
his time turned to the left side of the 
screen instead of along a more natural 
line of sight — straight ahead. 

Your screens will probably contain 
a variety of different types of infor- 
mation: title block, numerical infor- 
mation, prompt line, error-message 
line, operating-mode indicator, etc. 
Analyze your needs and determine 
how many different categories apply. 
Then allocate a screen area for each 
information category. 

Assure that information on screens 
does not stray from its assigned area. 
This is an application of the con- 
sistency principle discussed earlier. 
The more complex your screen dis- 
plays, the more important it is to 
allocate areas. If you have complex 
screens and do not design them con- 
sistently, you will confuse the 
operator. 

If possible, separate each area of 
the screen from the next by at least 
three rows or columns of blank 
spaces. Different blocks can also be 
separated by lines, which will make 
the separation more distinct. More ef- 
fective still is to color-code different 
screen areas. 

"Keep it simple" has become a 
cliche but is valuable and important 
advice. Unfortunately, keeping it 
simple is, to use another cliche, easier 
said than done. What, after all, is 
"simple"? And when is something "not 
simple enough?" 

Finding the answers to these ques- 
tions requires you to take a close look 
at the information needs of your pro- 
gram users at each point in your pro- 
gram. Present no more information 
than necessary. 

Some programmers use the "one 
logically connected thought or step 
per screen" rule. Where much infor- 
mation must be conveyed, these pro- 
grammers break it up into logical 
thoughts or steps and present each 
one on a separate screen. This is like 
the rule of presenting one idea in each 
paragraph of prose. 

Programmers in the "densely 
packed display" school of thought 
hold the view that if they can get 



122 April 1982 © BYTE Publications Inc 



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ZOBEX is trademark of ZOBEX CORPORATION 

IBM is trademark of International Business Machines Corporation 



Circle 446 on inquiry card. 



BYTE April 1982 123 



NOT THIS 



THIS 



Personnel Directory 
NAME 

Knuth 
Soms 
Lien 
Bowles 



King 

Grogono 

Liffick 







Personnel Directory 

NAME 

Bowles 
Grogono 
King 
Knuth 



Lien 

Liffick 
Soms 



Figure 4: The same list presented in random order and in alphabetical order. Recognizable orderings — e.g. , alphabetical, numerical, 
and chronological — make data easier for the operator to comprehend. 



everything onto one screen they are 
saving something. What, exactly, 
they are saving is unclear, although 
they must gain a certain satisfaction 
by rising to the challenge of making 
everything fit. This satisfaction 
resembles the exultation of the first 
guy who engraved the Declaration of 
Independence on the head of a pin. 
Judge for yourself how useful that 
was. 



In designing screen displays, it is 
important to follow prevailing con- 
ventions. Because of experience with 
written language, people have certain 
built-in expectations for the way in- 
formation will be presented to them. 
If you don't follow convention in dis- 
playing information, you make 
things more difficult for the operator. 

Think of your display screen as the 
page of a book. In a book, informa- 




tion is normally presented in lines 
that are read from left to right and 
from top to bottom. Numeric infor- 
mation is usually presented in tabular 
format, i.e., beneath column head- 
ings and from top to bottom. Certain 
obvious things you should avoid are 
printing numeric information from 
left to right or presenting very wide 
columns of text. If in doubt, recall 
how you have seen such information 
portrayed in books. 

You should display information in 
a recognizable order. Some screens 
present directories or lists through 
which the operator must search. A 
menu is one such list, although it is 
usually short, with the most frequent- 
ly called options listed at the top and 
the least frequently at the bottom 
(more on this later). Long directories 
or lists should be presented in an 
order that the operator will recog- 
nize, for example, alphabetic, numer- 
ic, or chronological order. This 
simplifies the search and saves time. 
Figure 4 shows the same information 
presented in random order and again 
in alphabetical order. Judge for your- 
self which ordering makes it easier to 
find the name "Grogono." 

Long strings should be broken up. 
A "long" string is one that has more 
than about five independent charac- 
ters. By "independent" we mean char- 
acters that do not unite to form a re- 
cognizable whole such as a person's 
name. A telephone number without 
the separating hyphen would be such 
a string. People have difficulty recog- 
nizing and separating the individual 
characters of long strings. If you have 



124 April 1982 © BYTE Publications Inc 



Circle 330 on inquiry card. 




I learned that I could get specific advantages when 
purchasing from A.E.I. 

A.E.I, has valuable knowledge gained from selling 
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technical questions, and expedite repairs to my 
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Calling A.E.I, is the smart thing todo. 

* A.E.I, does not wish to imply that any of these fine 
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NORTHSTAR SOFTWARE 




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TI-810 Full ASCII 1745 1479 

TI-810 Package 1945 1649 

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MORROW DECISION COMPUTER 

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Decision 1 BASIC 1725 1350 

65 K Static Ram 1000 780 

Switchboard I/O 259 210 

Select drives from Morrow disc systems 
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MORROW DISC SYSTEMS 



Discus 2D 1 Drive 
Discus 2D 2 Drive 
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CP/M & Microsoft Basic Included 



LINE PRINTERS 





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Okidata 82A 


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SYSTEMS GROUP 






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2800 Computer 


5035 


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DM-6400 Memory 


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735 


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460 


365 


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465 


370 



MICROPRO SOFTWARE 

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niCPPADI EC 



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Circle 44 on inquiry card. 



ACCOUNT REPORT 



DESCRIPTION 



Account #: 3281 
name : Budget 



STATUS 

This account is not currently up to date. 
Last payment was made 12 months ogo. 



ACCOUNT 


INFORMATION 






Balance 


$ 


31,000.00 




Payment 




292.89 


Amt 


Last Pmt 




3.69 



Figure 5: Standard methods of presenting text and numbers on the screen. Text is 
easier to read if left- justified. Numbers are easier to read if right-justified and aligned 
on the decimal point (if any). 



ever tried to count over to, say, the 
15th character of a 40-character 
string, you know the problem. 

Elements of the string can be more 
readily located if you display the 
string as several short strings, (i.e., 
consisting of five or fewer characters) 
separated by spaces. (Better yet, find 
an explicit, uncoded method to pre- 
sent your information.) 

According to standard practice, 
text is normally justified to the left 
side of the screen or to a defined tab 
value. Numerical information is nor- 
mally justified to the right. Where the 
number of decimal places may vary 
on successive lines, decimal points on 
all lines should align at a particular 
tab value. These conventions are 
carry-overs from mainframe practice, 
where the availability of sophisti- 
cated formatting statements makes 
alignment easy. Justifying numbers to 
the right and aligning decimal points 
are more difficult with most micro- 
computer BASICs, although subrou- 
tines for performing these functions 
have appeared in publications, and 
most moderately skilled program- 
mers can write their own. Figure 5 il- 
lustrates conventional alignment of 
information on the display screen. 

Sequence Control 

Sequence control is the manner in 
which the operator controls the se- 



quence of program operations. In 
menu-driven programs, the operator 
exercises sequence control through 
menu choices. These let the operator 
select the subprograms he needs to do 
his job. 

An operator can exercise sequence 
control in many other ways. Control 
simply requires an interaction or 
"dialogue" with the program. The 
menu-driven program permits a par- 
ticular type of dialogue. Other com- 
mon dialogue types are question and 
answer, query, program-like lan- 
guage, and action code. 

In question-and-answer dialogue 
the program displays a question and 
the operator responds with an 
answer. The expected answer is one 
of a limited set of alternatives, such as 
"yes" or "no." Example: Program 
asks whether output should be dis- 
played on video terminal or printer. 

Query dialogue is an extension of 
question and answer: a question is 
posed but the number of alternatives 
is large. Example: Program requests 
the number of the file it should dis- 
play. 

Program-like language dialogue 
uses a defined set of commands to 
control the program. Valid com- 
mands are usually brief mnemonic 
abbreviations of action words. Exam- 
ple: Command words used to control 
the Star Wars game. 



ISEisan 

International 

Consortium 

of the World's 

Leading Software 

and 

Consulting Firms, 

Representing 

Over5 # 000 

Professionals 

Around the World 

Major companies around the 
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P.O. Box 248 Lafayette, IN 47902 

For more on one of 
our fine products, see page 31 4 



126 April 1982 © BYTE Publications Inc 



T 

As inevitable as evolution. 



Mainframe solutions at micro prices. 

A new era has begun. With computer prices down and 
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Professional demand was inevitable. Software unavailable. 

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FIRST IN SOFTWARE TECHNOLOGY P.O.Box 1628 Champaign, IL 61820 (21 7) 359-21 12 Telex 270365 



PROMPTING LEVEL SELECTION MENU 
Please select desired level of prompting: 



1. Full 

2. Partial 

3. None 

Enter Choice # . 



Figure 6: Menu which allows the operator 
to choose the prompting level. Features 
like this accommodate operators who dif- 
fer in skill. 



Action code dialogue usually in- 
volves the use of specially defined 
and labeled function keys for calling 
up displays or programs. User-de- 
fined function keys are not widely 
available on microcomputers, but we 
will see more of them in the future. 
The new IBM Personal Computer has 
15 or more user-defined function 
keys. 

Beside these methods, sequence 
control can be exercised in a number 
of other ways — in fact, via any chan- 
nels that permit the operator to enter 
data into the computer and receive 
feedback. Possibilities include track- 
ball, joystick, optical device, human 
voice, and whatever else creative 
minds can invent and implement. 

The Old Standby— 

the Menu-Driven Program 

In this article I cannot cover 
sequence-control design principles 
that apply to all dialogue types. For 
one thing, there isn't room. But more 
important, the research with many of 
these methods is limited, and I can 
offer few definitive recommenda- 
tions. For these reasons, I will focus 
on that old standby, the menu-driven 
program. Though its origin is trace- 
able to the earliest days of computing 
machinery, the menu-driven program 
remains the principal means by which 
people carry on dialogues with com- 
puters. Until people perfect ways of 
talking with computers, the* menu- 
driven program will probably remain 
the mainstay. 



There are good reasons for its 
popularity and success. First, it 
makes no demands on human mem- 
ory. Menu options are displayed on 
the screen and the operator picks the 
one he wants. This makes a menu- 
driven program easy to learn. Sec- 
ond, menus help the operator orient 
himself because they explicitly dis- 
play the available "roads" (sub- 
programs) from each "crossroad" 
(menu). 

Menu-driven programs have cer- 
tain drawbacks as well. Storing and 
generating menus cost memory and 
time overhead. Once familiar with a 
program, operators may find that 
layers of menus impede progress 
more than they help. 

For all that, the menu-driven pro- 
gram is a good vehicle for our discus- 
sion of sequence control because most 
people are familiar with it. Many of 
the design principles I will discuss in 
relation to it can be extended to other 
types of dialogues as well. 

Your menu-driven program should 
be self-explanatory. The operator 
should not have to refer constantly to 
a manual to figure out how to make 
something happen. Obviously, you 
cannot explain everything within the 
program, but you should provide 
screens that describe special se- 
quence-control features. For example, 
suppose that your program has 
several subprograms, each containing 
sub-subprograms, and so on, and 
that different program levels are ac- 
cessed through layers of menus. Sup- 
pose further that you have designed 
certain sequence-control features to 
shortcut some menus so that the ex- 
perienced operator can move quickly 
around to different parts of the pro- 
gram. Special features such as these 
should be explained within the pro- 
gram, either on separate screens 
which precede menus or, if the ex- 
planation is brief enough, on menus 
themselves. 

Your program will function, of 
course, without built-in screen docu- 
mentation. However, the operator 
will learn the intricacies of your pro- 
gram much more quickly if you do 
your explaining when and where he 
needs it — within the program itself. 



If the operators using your pro- 
gram will vary in skill level, attempt 
to build in features that will accom- 
modate skill growth. For example, let 
the operator select the level of 
prompting — full, partial, or none. 
This will help the inexperienced 
operator gain skill and confidence 
and save the experienced operator a 
lot of time. Make the choice of the 
prompting-level convenient, as 
shown in figure 6. 

Your program may have one menu 
or several, depending on complexity. 
If it is a complex program with many 
options, analyze how each sub- 
program will be used. Determine 
which subprograms are functionally 
related. Estimate how often each 
menu choice will be made. You may 
be able to make a very long menu 
into a number of short ones. 

Functional relationships and fre- 
quency of use of the subprograms are 
the two most important criteria to 
consider in designing a menu. List 
functionally related subprograms on 
the same menu. If possible, list fre- 
quently called subprograms on the 
same menu. If these requirements 
conflict, let functional relationships 
rule menu design. Avoid designing 
very long menus that contain a grab 
bag of unrelated options. This only 
makes sense if all programs are equal- 
ly likely to be called under all condi- 
tions. That is seldom the case. 

Make menu choices brief, explicit, 
and distinct from one another. To 
make up the label, consider exactly 
what each subprogram does and then 
label it accordingly. 

Use terminology consistently. For 
example, don't call subprograms that 
do essentially the same thing by dif- 
ferent names in the same program — 
don't call a program "edit" in one 
place and "modify/delete" in 
another. 

The menu itself has three essential 
parts: (1) title, (2) list of menu 
choices, and (3) prompt line. Some 
menus also contain a statement that 
directs the operator to "select one of 
the menu choices." This feature is 
useful to operators unfamiliar with 
computers and can be considered op- 
tional. 



130 April 1982 © BYTE Publications Inc 



Circle 111 on inquiry card. 




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132 April 1982 © BYTE Publications Inc 



MAIN MENU 

Select one of the following programs by 
entering its number 

1. ENTER DATA 

2. GENERATE REPORTS 

3. EDIT DATA BASE 

4. START NEW FILE 

5. PURGE FILE 

6. QUIT 

Enter Choice #_ 



Figure 7: Menu showing the three essen- 
tial menu parts: title, list of choices, and 
prompt line. Some menus also have a 
directive to prompt operators unfamiliar 
with the system. 

Center the menu title at top of the 
display and put the word "menu" at 
the end of the title. If you are pro- 
viding the (optional) directive line, 
print this next, offset to the left, so 
that it is recognized as an instruction 
and not a title. Center the prompt and 
the data input field at the bottom of 
the screen. The prompt should be 
brief and explicit, for example, 
"ENTER CHOICE #," as shown in 
figure 7. 

Menu selection can be done in 
several different ways: by entering 
the number of a menu option, by 
entering a letter, by typing in the 
menu choice, and by moving a cursor 
to the choice. Typing in the menu 
choice label usually requires several 
keystrokes and should be avoided. 
Most microcomputer software is not 
set up to permit cursor selection of 
menu choices. 

The most common selection 
method is to type in a number or 
letter. In general, short menus should 
permit selection by letter — preferably 
the first letter of the choice label. 
(This can present problems if dif- 
ferent menu choices start with the 
same letter.) On longer menus, num- 
bered menu choices are more conve- 
nient. 

If you do use numbers, then any 
list of numbered items appearing on 
one of your display screens will 
resemble a menu. This may cause 
confusion. Minimize confusion by ti- 
tling menus as menus and titling other 
displays appropriately. Avoid num- 
bered items on nonmenu displays, if 



possible. If you are presenting a list of 
instructions, for example, precede 
each instruction by a bullet instead of 
a number. 

Conclusion 

This brief excursion into the world 
of human factors covered areas of in- 
terest to the average microcomputer 
programmer. Much more is written 
on the subject, and those interested 
should consult the references listed at 
the end of this article. 

Note that application of human- 
factors considerations to software 
design is immature as a technology 
and that much research still needs to 
be done. At present there is no single 
source to which the reader can refer 
to find all the important answers. 
(Martin's book is comprehensive but 
aimed primarily at the mainframe 
user.) Much of what is now available 
comes as technical reports that pre- 
sent recommendations cautiously 
labeled as ''preliminary'' or 
"tentative" findings. 

In this article, I have attempted to 
congeal this somewhat indefinite 
material into a form that is useful to 
the average reader. Much has been 
left out because of inapplicability to 
microcomputers or because the 
material was of a specialized nature 
and would probably not be of in- 
terest. In general, what was presented 
is based on the references, although at 
some points I have condensed and 
simplified things. I hope that I have 
not distorted any author's intentions 
in the process. ■ 

References 

1 . Anacapa Sciences Inc. "Fundamentals of 
Human Factors for Engineering and De- 
sign — Session 22: Human-Computer 
Interface Design" (classroom notes from 
seminar). Santa Barbara, CA: 1981. 

2. Engel, S. E., & Granda, R. E. Guidelines for 
Man/Display Interfaces, Technical Report 
TR 00.2720. Poughkeepsie, NY: IBM, 
December 19, 1975. 

3. Martin, J. Design of Man-Computer 
Dialogues. Englewood Cliffs, NJ: Prentice- 
Hall, 1976. 

4. Smith S. L. Man-Machine Interface: Re- 
quirements Definition and Design Guide- 
lines — a Progress Report, Project No. 
572R. Bedford, MA: Mitre Corporation, 
February 1981. 



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The Atari Tutorial 

Part 8: Generating Sound with Software 

The sound capabilities of the Atari 400 and 800 computers 
are influenced by the software technique used. 



Bob Fraser 

1639 Martin Ave. 

Sunnyvale, CA 94087 



The sound system in the Atari 400 
and 800 microcomputers can be used 
in two basic ways: static and 
dynamic. Static sound generation is 
the simpler of the two. The program 
sets a few sound generators, turns to 
other activities for a while, and then 
turns them off. Dynamic sound 
generation is more difficult. The com- 
puter must continuously update the 
sound generators during program ex- 
ecution. For example: 

SOUND 0,120,8,8 

generates a static sound, while: 

FORX = 0TO255 
SOUND 0,X,8,8 
NEXTX 

generates a dynamic sound. 



This article appears in slightly different form 
in De Re Atari, published by Atari Inc., and is 
reproduced with its express permission. 



Static Sound 

Although static sound is normally 
limited to beeps, clicks, and buzzes, 
there are exceptions. Two examples 
are the programs given last month as 
special effects in the sections on high- 
pass filters and 16-bit sound. Another 
way to obtain interesting effects is to 
use interference, as in this example: 

SOUND 0,255,10,8 
SOUND 1,254,10,8 

The strange effect is a result of 
closely phased peaks and valleys. 
Figure 1 shows two channels in- 
dependently running sine waves at 
slightly different frequencies and their 
sum. The sum curve shows the 
strange interference pattern created 
when these two channels are added. 

Figure 1 also shows that, at some 
points in time, the waves are assisting 
each other; at other points, they op- 
pose each other. Adding the volumes 
of two waves whose peaks coincide 
will yield a wave with twice the 



strength or volume. Similarly, adding 
the volumes of two waves while one 
is at maximum and the other is at 
minimum will result in a cancellation 
of both of them. On the graph of the 
sum curve, we can see this effect. An 
interesting project would be writing a 
program to plot interaction patterns 
of two, three, and four channels; the 
program would display graphs like 
that of figure 1. You might discover 
some unique sounds. 

The slighter the difference in fre- 
quency between the two channels, the 
longer the pattern of repetition. To 
understand this, draw some graphs 
similar to figure 1 and study the in- 
teraction. As an example, try the 
following BASIC statements: 

SOUND 0,255,10,8 
SOUND 1,254,10,8 
SOUND 1,253,10,8 
SOUND 1,252,10,8 

As the difference in frequency grows, 
the period of repetition decreases. 



134 April 1982 © BYTE Publications Inc 



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BYTE April 1982 135 



Minicomputer performance in 



Multi-user. Multi Tasking. Decision I™ memory man- 
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5221 Central Avenue, Richmond, CA 94804 
(415) 524-2101 



Circle 284 on inquiry card. 



CHANNEL 1 



CHANNEL 2 



CHANNEL 1 
+ 
CHANNEL 2 




POSITIVE + NEGATIVE = ZERO 
NEGATIVE + NEGATIVE = DOUBLE NEGATIVE 
POSITIVE + POSITIVE = DOUBLE POSITIVE 



Figure 1: Complex waveform generation from the addition of waveforms. 



Listing 1: Using machine language to assist BASIC in generating multiple-note chords on 
the Atari 400/800. This demonstration program uses a short machine-language program 
placed in the BASIC string SIMUL$ (see lines 25 and 9999) to specify the frequency- and 
control-register values of up to four of the Atari sound generators. It is done quickly 
enough to make all the generators seem to start simultaneously (BASIC is too slow to do 
this). Note the use of the string SIMULS to store the machine-language program and the 
USR call in line 50 to execute it. 

10 SOUND 0,0,0,0:DIM SIMUL$(16) 

15 REM read in machine lang. program 

20 RESTORE 9999:X = 1- 

25 READ Q: IF Q<> -1 THEN SIMUL$(X) =CHR$(Q):X = X + l:GOTO 25 

26 REM read and then play sound data 

27 RESTORE 100 

30 READ F1,C1,F2,C2,F3,C3,F4,C4 

40 IF Fl = - 1 THEN END 

50 X = USR(ADR(SIMUL$) / F1 / C1 ,F2,C2,F3,C3,F4,C4) 

55 FORX = 0TO 150:NEXT X 

60 GOTO 30 

90 REM sound data 

100 DATA 182,168,0,0,0,0,0,0 

110 DATA 162,168,182,166,0,0,0,0 

120 DATA 144,168,162,166,35,166,0,0 

130 DATA 128, 168, 144, 166,40, 166,35, 166 

140 DATA 121,168,128,166,45,166,40,166 

150 DATA 108,168,121,166,47,166,45,166 

160 DATA 96, 168, 108, 166,53, 166,47, 166 

170 DATA 91,168,96,166,60,166,53,166 

999 DATA -1,0,0,0,0,0,0,0 

9000 REM 

9010 REM 

9020 REM this data contains the machine lang. program, 

9030 REM and is read into SIMUL$ 

9999 DATA 104,133,203,162,0,104,104,157,0,210,232,228,203,208,246,96,-1 



Dynamic Sound 

More complex sound effects nor- 
mally require the use of dynamic 
sound techniques. Three levels of 
dynamic sound generation are 
available to the Atari 400/800 pro- 
grammer: sound in BASIC, 60-hertz 
(Hz) interrupt sound, and sound in 
machine code. 

BASIC Sound 

BASIC is somewhat limited in its 
handling of sound generation. As you 
may have noticed, the SOUND state- 
ment negates any special AUDCTL 
setting. [The audio-control register 
AUDCTL was discussed in last 
month's installment of "The Atari 
Tutorial." . . . GW] This problem 
can be avoided by poking values 
directly into the sound registers, 
rather than using the SOUND state- 
ment. 

In addition, the use of BASIC to 
control sound generation is 
somewhat limited because of its 
slowness. If the program is not com- 
pletely dedicated to sound genera- 
tion, there is seldom enough pro- 
cessor time to do more than static 
sound or choppy dynamic sound. 
The only alternative is to temporarily 
halt all other processing while 
generating sound. 

Another problem can occur when 
using the computer to play music on 
more than one channel. If all four 
channels are used, the time separation 
between the first SOUND statement 
and the fourth can be substantial 
enough to make a noticeable delay 
between the different channels. 

The program in listing 1 solves this 
problem. SIMULS is a tiny machine- 
language program that pokes all four 
sound channels very quickly. A 
BASIC program using SIMULS can 
rapidly manipulate all four channels. 
Any program can call SIMULS by 
putting the sound-register values in- 
side the USR function as in line 50 of 
the demonstration program. The 
parameters should be ordered as 
shown, with the control-register 
value following the frequency- 
register value for each channel; this 
ordering is followed one to four 
times, once for each sound channel to 



138 April 1982 © BYTE Publications Inc 



8086 Super-micro 

8 Mhz. - 16-bit - S-100 bus - 128K 70 nsec. RAM 



Computer Benchmarks - All systems running the same BASIC program. 



Manufacture - Model Class Operating 

System 

IBM 3033 Mainframe VS2-10RVYL 

Seattle Computer System 2 Micro MS-DOS 

Digital Equipment PDP 11/70 Mini n/a 

Prime 550 Mainframe PRIMOS 

Digital Equipment PDP-10 Mainframe TOPS-10 

IBM System 34 Mainframe Release 05 

TEI System 48 Micro MAGIC 1.0 

Hewlett-Packard HP3000 Mini Time Share 

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Alpha Micro AM-100/T Micro AMOS 4.3a 

Digital Equipment PDP 11/45 Mini n/a 

Data General NOVA 3 Mini Time Share 

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North Star Floating Point Micro NSDOS 

Radio Shack TRS-80 II Micro TRSDOS 1.2 

Apple 11+ Micro DOS 3.2 

Cromemco System 3 Micro CDOS 

Commodore Pet 2001 Micro n/a 

IBM 5100 Micro n/a 

Vector MZ Micro n/a 



Language 
(Type*) 

Stanford BASIC 
Microsoft BASIC (C) 
BASIC (I) 
BASIC V16.4 (I) 
BASIC (I) 
BASIC (I) 

Microsoft BASIC (C) 
BASIC (I) 

Microsoft BASIC (I) 
Alpha BASIC (SC) 
BASIC (I) 
BASIC 5.32 
Level 1 BASIC (I) 
NorthStar BASIC (I) 
BASIC (I) 
Applesoft II (I) 
32K BASIC (I) 
Microsoft BASIC (I) 
BASIC (I) ' 
Micropolis BASIC (I) 



Run Time 
(Seconds) 

10 

33 

45 

63 

65 

129 

178 

250 

310 

317 

330 

517 

680 

685 

792 

960 

1074 

1374 

1951 

2251 



• C = Compiler; I = Interpreter. Times (except for Seattle Computer) taken from August 1981 issue of Interface Age. 

Seattle Computer System 2 consists of 8 Mhz. 8086 CPU set, 128K of 70 nsec. static RAM, double- 
density disk controller, 2 2 -slot TEI constant voltage mainframe, a cable for two 8' drives, and 
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Price: $4185. 8087 Adapter also available. 



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• BASIC-86 Interpreter $400 

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Information Hotline 
206/575-1830 



Circle 367 on inquiry card. 



BYTE April 1982 139 




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140 April 1982 © BYTE Publications Inc 



be set. As a speed consideration, as 
well as a convenience, SIMUL$ 
allows you to specify sound for less 
than four channels (i.e., channels 1 
through 3, channels 1 and 2, or just 
channel 1). Simply omit the unused 
parameters from the USR function. 

SIMUL$ offers another distinct ad- 
vantage to the BASIC programmer. 
The AUDCTL register is reset upon 
execution of any SOUND statement 
in BASIC. However, using SIMUL$, 
no SOUND statements are executed; 
thus, the AUDCTL setting is retained. 

Another method of sound genera- 
tion in BASIC is impractical. This 
method uses the volume-only bit of 
any of the four audio-control 
registers. Type in and run the follow- 
ing program: 

SOUND 0,0,0,0 
10 POKE 53761,16: 

POKE 53761,31: 

GOTO 10 

This program sets the volume-only 
bit in channel 1 and modulates the 
volume from to 15 as fast as BASIC 
can. Although it uses all the process- 
ing time available to BASIC, it pro- 
duces only a low buzz. 

60-Hz Interrupt 

This technique is probably the 
most versatile and practical of all 
methods available to the Atari com- 
puter programmer. 

Precisely every 1/60 second the 
computer hardware automatically 
generates an interrupt. When this 
happens, the computer temporarily 
leaves the main program (the pro- 
gram running on the system — 
BASIC, Star Raiders, etc.). It then ex- 
ecutes an interrupt service routine, a 
small machine-language routine 
designed specifically for servicing 
these interrupts. When the interrupt 
service routine finishes, it executes a 
special machine-language instruction 
that restores the computer to the in- 
terrupted program. This all occurs in 
such a way (if done properly) that the 
program execution is not affected. In 
fact, it has no idea that it ever 
stoppedl 

The interrupt service routine cur- 
rently resident on the Atari 400/800 



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computers maintains timers, trans- 
lates controller information, and per- 
forms other chores requiring regular 
attention. 

Before the interrupt service routine 
returns to the main program, it can be 
made to execute any user routine — 
for example, your sound-generation 
routine. This is an ideal situation for 
sound generation since the timing is 
precisely controlled, and especially 
since another program can be 
executing without paying heed to the 
sound generator. Even more im- 
pressive is its versatility. Because it is 
a machine-language program, the 
interrupt sound program will lend 
itself equally well to a main program 
written in any language — BASIC, 
assembly language, FORTH, Pascal. 
In fact, the sound generator will re- 
quire few, if any, modifications to 
work with another program or even 
another language. 

A table-driven routine offers max- 
imum flexibility and simplicity for 
such a purpose. Table-driven refers to 
a type of program that accesses data 
tables in memory for its information. 
In the case of the sound generator, the 
data tables would contain the fre- 
quency values and possibly the 
audio-control-register values. The in- 
terrupt service routine would simply 
read the next entries in the data table 
and put them into their respective 
audio registers. Using this method, 
notes could change as often as 60 
times per second, fast enough for 
most applications. 



Once such a program has been 
written and placed in memory (for 
example, at location 600 hexa- 
decimal, the beginning of the page of 
memory reserved for the user), you 
need to install it as a part of the 60-Hz 
interrupt service routine. This is 
accomplished by a method known as 
vector stealing. 



Direct control of sound 
registers with a 
dedicated machine- 
language routine opens 
new doors in sound 
generation. 



Memory locations 224 and 225 
hexadecimal contain the address of a 
small routine called XITVBL (eXIT 
Vertical BLank interrupt service 
routine), which is designed to be 
executed after all 60-Hz interrupt pro- 
cessing is complete, restoring the 
computer to the main program as 
previously discussed. 

The following procedure shows 
how vector stealing can be used to in- 
stall your sound routine: 

1. Place your program in 
memory (e.g., 600 hexa- 
decimal). 

2. Verify that the last instruction 
executed is a JMP $E462 (since 
location E462 hexadecimal is 



the XITVBL routine, this will 
make the main program con- 
tinue). 

3. Load the X register with the 
high byte of your routine's 
address (a 6 in this case). 

4. Load the Y register with the 
low byte of your routine's 
address (a in this case). 

5. Load the accumulator with a 
7. 

6. Do a JSR $E45C (to set loca- 
tions 224 and 225 hexa- 
decimal). 

Steps 3 through 6 are required to 
change the value of the pointer at 
locations 224 and 225 hexadecimal 
without error. The routine called is 
SETVBV (SET Vertical Blank Vec- 
tors), which simply puts the address 
of your routine into locations 224 and 
225 hexadecimal. Once installed, the 
system works as follows when an in- 
terrupt occurs: 

1. The computer's interrupt 
routine is executed. 

2. The computer jumps to the 
program whose address is in 
locations 224 and 225 hexa- 
decimal, which is now your 
routine. 

3. Your routine executes. 

4. Your routine then jumps to 
XITVBL. 

5. XITVBL restores the com- 
puter's state previous to the in- 
terrupt and makes it resume 
normal operation. 



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GRAPHIC SOFTWARE FOR 

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ENGINEERING SOFTWARE FOR MICROS -A self- 
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Books contain fully documented program listings in BASIC with theory and equations. Disks contain the same programs as the books but 
without documentation. When ordering disks, please specify APPLE II Plus 48K DOS 3.3 or CP/M. 



142 April 1982 © BYTE Publications Inc 



Circle 229 on inquiry card. 



[An elusive and infuriating "bug" 
may occur when a 60-Hz interrupt 
routine involving arithmetic opera- 
tions (ADC and SBC op codes) is 
used as part of a BASIC program. 
The Atari BASIC floating-point 
routines set the 6502 decimal flag and 
cause add and subtract operations to 
be done in binary-coded decimal 
(BCD) instead of binary. If the 60-Hz 
interrupt occurs during a BASIC 
floating-point operation, the inter- 
rupt routine will be in decimal — not 
binary — mode unless you execute a 
CLD instruction at the beginning of 
the routine. My thanks to Chris 
Crawford of Atari for pointing out 
this bug. . . . GW] 

If you do not wish to implement 
such a program yourself, one is 
available from the Atari Program Ex- 
change. The package is called IN- 
SOMNIA (Interrupt Sound Initial- 
izer/ Alterer). It allows creation and 
modification of sound data while you 
listen and is accompanied by an inter- 
rupt sound generator that is table- 
driven and compatible with any 
language. For more information, con- 
tact the Atari Program Exchange, 155 
Moffett Park Dr., POB 427, Sunny- 
vale, CA 94086. 

Machine-Code Sound Generation 

Direct control of sound registers 
with a dedicated machine-language 
routine opens new doors in sound 
generation. The technique is as 
follows: write a program similar to 
the 60-Hz interrupt routine in that it 



is table-driven. However, the only 
routine now being executed by the 
Atari is dedicated to sound genera- 
tion. By expending much more pro- 
cessor time on sound generation, you 
can produce higher-quality sounds. 
Consider, for example, the output of 
a typical 60-Hz interrupt music 
routine; its output will look 
something like figure 2a. 



The volume-only bit 
offers a tremendous 
capacity for accurate 
sound reproduction. 



Since much more processing time is 
available with a dedicated machine- 
language routine, you can change the 
frequency at very high speed during 
the note's playing time. For example, 
suppose you discover that whenever 
any piano key is struck it produces 
the characteristic sequence of fre- 
quencies shown in figure 2b. 

The graph in figure 2b is called the 
piano envelope. To simulate a piano, 
the idea is to apply the piano 
envelope very quickly to the "plain- 
vanilla" square-wave beep. The note 
is thus slightly modified during its 
playing time. For example, a piano 
simulation of the three notes in figure 
2a would be modified to look like 
figure 2c. This is essentially the same 
sound produced by the standard 
music routine of figure 2a, only the 



(2a) 



1 NOTE 



TIME 



(2b) 



-^r 



TIME 



(2c) 



k—\ 



ry/W — ' 



w—\ 



TIME 



Figure 2: Complex waveform generation 
under computer control Figure 2a shows 
a frequency -versus-time plot of three sim- 
ple notes generated by one of the Atari 
sound generators. If the complete 
resources of the computer are used to 
modulate the frequency (or other 
parameters) of the notes while they are be- 
ing played, the computer can produce 
highly complex sounds. For example, if 
we find that a frequency envelope such as 
figure 2b simulates the sound of a piano, 
the envelope can be superimposed on the 
generated notes of figure 2a to give a 
modified set of notes that has a graph like 
that of figure 2c. 



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PUBLICATIONS 1 90 Duck Hill Road. P. 0. 1 029A, Duxbury , MA 02332. Add $2 per book 4th cl postage in US and Canada; $3 1 st cl or U PS in 
US; $4.50 1st cl Canada; $12 air Europe and Central America; $18 elsewhere. Call (617) 934-0445 for faster delivery. 



190 Duck Hill Rd 
Duxbury, MA 02332 



Clrcle230on inquiry card. 



April 1982 © BYTE Publications Inc 143 





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Listing 2: A machine-language program that uses the waveform mode of the Atari 400/800 to generate tones with a sine wave 
amplitude envelope (tones normally produced by the Atari have a square-wave amplitude). 



0100 
0110 
0120 
0130 
0140 
0150 
0160 
0170 
0180 
0190 
0200 
0210 
0220 
0230 
0240 
0250 
0260 
0270 
0280 
0290 
0300 
0310 
0320 
0330 
0340 
0350 
0360 
0370 
0380 
0390 
0400 
0410 
0420 
0430 
0440 
0450 
0460 
0470 



VONLY 



Bob Fraser 7-23-81 



volume-only AUDC1-4 bit test routine 



AUDCTL=$D208 
AUDF1=$D200 
AUDC1=$D201 
SKCTL = $D20F 



TEMPO 
MSC 



* = $B0 
.BYTE 1 
.BYTE 



*=$4000 
LDA#0 
STA AUDCTL 
LDA #3 
STA SKCTL 
LDX §0 



LOO 



LDA/jfO 

STA $D40E ; disable vertical blank interrupt 
STA $D20E ; disable nonmaskable interrupts 
STA $D400 ; disable screen DMA 



LDA DTAB,X 
STA MSC 



0480 




LDA VTAB,X 


0490 


L0 


LDY TEMPO 


0500 




STA AUDC1 


0510 


LI 


DEY 


0520 




BNEL1 


0530 






0540 




dec most significant counter 


0550 




DEC MSC 


0560 




BNEL0 


0570 






0580 






0590 




new note 


0600 






0610 




INX 


0620 




CPXNC 


0630 




BNE LOO 


0640 






0650 




wrap note pointer 


0660 




LDX/jfO 


0670 




BEQ LOO 


0680 






0690 






0700 ] 


VC 


.BYTE 28 ; note count 


0710 






0720 




table of volumes to be played in succession 


0730 1 


^TAB 




0740 




.BYTE 24,25,26,27,28,29,30,31 


0750 




.BYTE 30,29,28,27,26,25,24 


0760 




.BYTE 23,22,21,20,19,18,17 


0770 




.BYTE 18,19,20,21,22,23 


0780 






0790 




this table contains the duration of each entry 
above 


0800 ] 


DTAB 




0810 




.BYTE 1,1,1,2,2,2,3,6 


0820 




.BYTE 3,2,2,2,1,1,1 


0830 




.BYTE 1,1,2,2,2,3,6 


0840 




.BYTE 3,2,2,2,1,1 



notes now have a piano tone and they 
sound much prettier than just un- 
modulated beeps. Unfortunately, all 
other processing had to be sacrificed 
to get that piano tone. The sound 
channel is no longer updated only 
once every note; it is now done 
perhaps 100 times within the note's 
duration. 

Volume-Only Sound 

As indicated earlier, the AUDCrc 
volume-only bits aren't of much use 
in BASIC. This is due entirely to the 
fact that BASIC is too slow to effec- 
tively use them. However, this is not 
the case with machine language. 

As mentioned last month, the 
volume-only bit of the AUDCrc 
registers offers a tremendous capacity 
for accurate sound reproduction. 



True waveform generation (within 
the time and volume resolution limits 
of the computer) is made possible 
with this bit. Instead of just putting a 
piano flavor into the music, you can 
now make it closely replicate a piano 
sound. Unfortunately, it can never 
precisely duplicate an instrument. 
Four bits (16 values) is not enough 
volume resolution for true high- 
quality work. Nevertheless, the 
technique does generate surprisingly 
good sounds. The program in listing 2 
demonstrates the use of one of the 
volume-only bits. If you have an 
assembler, type it in and try it. Sur- 
prisingly, speed is not really a prob- 
lem here. The wave has almost sixty 
steps, and the program can still be 
made to play the wave at up to 10 
kilohertz. 



Remove lines 390 through 410 and 
try the program once more. It will 
sound quite broken up. The cause is 
the 60-Hz interrupt discussed in the 
previous section. You can actually 
hear the interrupts taking place since 
all sound stops during that time. 

Line 410 disables screen DMA 
(direct memory access). By disabling 
screen DMA, the ANTIC chip within 
the Atari 400/800 no longer "steals" 
time from the 6502 processor to get 
data from screen memory in time to 
display it on the video display. This is 
why the screen goes to a solid 
background color when the program 
is executed. Disabling screen DMA 
serves two purposes: to speed up the 
6502 processor and to make the tim- 
ing consistent, since screen DMA 
steals cycles at odd intervals. 



146 April 1982 © BYTE Publications Inc 



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BY TECMAR 

256 Dynamic Ram Card 

Hl-Speed Parallel I/O Card CALL 

Hi-Speed Serial I/O Card £°R 

Real-Time System Clock ddj^Jc 

Card Expansion Chassis PRICES 



Ordering Information: Phone orders using VISA, MASTER- 
CARD, AMERICAN EXPRESS, DINER'S CLUB, CARTE 
BLANCHE, bank wire transfer, cashier's orcertifiedcheck, 
money order, or personal check (allow ten days to clear). 
Unless prepaid with cash, please add 5% for shipping, 
handling and Insurance (minimum 5.00). California 
residents add 6% sales tax. Foreign customers please call 
or write for shipping information and charges. OEM's, In- 
stitutions and corporations please send for a written 
quotation. All equipment Is subjecct to price change and 
availability without notice. All equipment Is new and com- 
plete with manufacturer's warranty (usally 90 days). 
Showroom prices may differ from mall order prices. 

Send Orders to: 

G@[]uQ[°)Qaft®[7§ Mailorder 

8338 Center Drive 
La Mesa, California 92041 




*On all prepaid cash orders 
- Continental US Only 



APPLE II 
ACCESSORIES 



VIC ACCESSORIES 

8K Ram Cartridge for VIC-20 $50 

3K Ram Cartridge for VIC-20 $34 

Superslot $24 

Super Alien $24 

Jupiter Lander $24 

Draw Poker $24 

VIC Software 6 pack 'A' $49 

VIC Software 6 pack 'B' $49 

Datasette Cassette I/O Unit $69 

VIC IEEE-488 Interface $79 

Vicmon Machine Lang Monitor $47 

VIC Super Expander $54 

VIC RS232C Terminal Interface $39 

Voice Synthesizer CBM/PET $319 

Pgrm Char Set/Game Graphics ED $13 

3D Invaders $31 

Spiders of Mars $39 

Outworld $32 

Satellites and Meteorites $39 

Allen Blitz $32 

RS-232 Communicator Interface $40 

1 8 In. Communicator Cable M/M $13 

36 In. Communicator Cable M/M $15 

3K R AM Expander for VIC-20 $65 

8K RAM Expansion for VIC-20 $99 

VIC-20 Reference Card $4 

VICTermA $16 

Vicalcfor VIC-20 $11 

VIC Portfolio Mgmt. (VPM) $19 

VICHECK $19 

PACItln $15 

Amok $15 

Don't Fall $11 

Simon $7 

Blastoids $16 

Superadditon $7 

Supersubtraction $7 

Skymath $12 

Space Division $12 

Long Division $12 

Super Hangman $17 

BK ROM/RAM 25 

Alien Blitz $19 

Globber $19 

The Alien (Req. 6K memory) $19 

Invader Fall (Req. 6K memory) $17 

StarWars $13 

3D Maze $11 

Breakout $11 

Carom $11 

Raceway $11 

LazerWar $14 

Dragon Maze $13 

Shape Matcher $9 

Doggy Maze $9 



16K RAMBOARD by ConComp 
for Apple II Computers 



FOR ONLY 





16K Ram Board by ConComp Industries 

Hayes Mlcromodem II 299 

Hayes Smartmodem 369 

Hayes Chronograph 199 

NovationAppleCat 339 

Novation Cat Modem 169 

Novation Expansion Mod 39 

Novation Handset 29 

Novation BSR 19 

Vldex Videoterm 8 column card 249 

Vldex Keyboard Enhancer (Rev. 6) 115 

Vldex Keyboard Enhancer(Rev.7) 99 

Vldex Keyboard Enhancer II (Rev. 7 & up) 129 

Videx Swltchplate 15 

Vldex Soft Video Switch 29 

Z-80 Softcard by Microsoft 299 

Applesoft Compiler 149 

Typing Tutor II 20 

Microsoft Adventure 25 

Olympic Decathaion 24 

16K RamCard by Microsoft 159 

Thunderclockclock/calendercard 129 

Thunderclock X-10 Inter/Scheduler 49 

Smarterm 80 col card 299 

Corvus Winchester Disk Drives CALL 

ALF 3 Voice Music Card 199 

ALF 9 Voice Music Card 149 

Alphasyntaurl keyboard system CALL 

LazerLowerCase + 55 

Lazer Keyboard Plus + 99 

23 Key Numeric Keypad by Keyboard Co 120 

Joystick by Keyboard Co 45 

6809 CPU Card (The Mill) by Stellatlon 319 

AIO Serial & Parallel Interface by SSM A&T 189 

DB Master by Stoneware 189 

Music System (16 voices) 299 

A/D + D/A Interface 279 

Expansion Chassis (8 slots) 569 

lntroi/X-10 Controller card 169 

Clock/Calendar Card 225 

CPS Multi-function Card 175 

Supertalker SD-200 159 

Romplus + card 135 

Romwrltercard 149 

SymtecHI-Res Light Pen 210 

Sup-R-Fan 45 

Sup-R-Termina 1 329 

SVAZVX4 MegabyterS" Disk Controller 649 

SVA 2 + 2 Single Den. 8" Disk Controller 345 

Speechlink 2000 by Heuristics 249 

Versawrlter DlgitizerTablet 229 

Asynchronous Serial Interface card by CCS 1 39 

Centronics Parallel Interface card by CCS 119 

VlsiCalc version 3.3 1 69 

VIsiFlle (NEW data base manager) 199 

VisiTrend/VlsiPiot 219 

VisiDex 169 

VIsiTerm 99 

Desktop Plan II 169 

Wordstar (Apple 80 col version) 299 

VisiPak (Calc, Trend, Plot, File) 550 

Easywriter Word Processor 199 

Tax Preparer '81 version 89 

Real Estate Analyzer 129 

Creative Financing 139 

Personal FilingSystem(PFS) 79 

PFS...Report 79 

Datastar (Apple II - 80 col) 249 

Spell Star (Apple II - 80 col) 219 

Super-sort (Apple II - 80 col) 179 

Peachtree Accounting Software .CALL 

BPIAccountingSoftware CALL 

Systems Plus Accounting Software CALL 



CALL OR 
WRITE FOR 

FREE CATALOG 



NO RISK* MAIL ORDER DISCOUNTS 



*Call for 
Details 



ORDER TOLL FREE 

800-854-6654 



In California and 
outside continental U.S. 



(714) 698-8088 Telex 6950 »« 

* ' BetaCCMO 



Circle 126 on inquiry card. 





H commodore 

CBM 

Business 
Computer 



CALL FOR BEST PRICES 

73 Key Typewriter Style Keyboard 

80 x 25 Column/Line Video Display 

Integrated 9" Green Phosphor Monitor Standard 

Inverse & Overstrike Characters 

Full Screen editing capability Built-in 

Built-in Parallel I/O Port 

IEEE-488 Bus Interface Capability Standard! 

2 Cassette Ports 

18K ROM BASIC (Version 4.0) 

9 Digit Floating Point Binary Arithmetic 

Sophisticated Disk & Tape Handling Software 
We couldn't tell you all the things the Commodore CBM 
system could do for your home or office, but think about 
hiring a secretary, an accountant, and a financial advisor 
all for the price of a Commodore CBM 8000 Computer! 
Just add the Commodore 4040 or 8050 dual floppy disk 
drive, and a printer of your choice, and you've got a fully in- 
tegrated system, ready to bring the computer revolution 
into your home or business! Start your revolution now at 
Consumer Computers. 

MASS STORAGE DISK DRIVES AVAILABLE ACCOUNT- 
ING SOFTWARE AND SPECIALIZED MARKET SOFT- 
WARE TOO! 




DET Personal 
"C I Computer 



At Consumer Computers we're experts in 
the business of selling computer products 
by mail. We have become one of the leaders 
not only because our prices are better, but 
because of the reputation we've worked 
hard to earn. Over the years we have learn- 
ed what you, the customer, want and need 
from a mail order company. If we offer any 
merchandise that you're in the market for, 
you should seriously compare what we 
have to offer over the others. Here are just a 
few of the reasons. 

Our helpful salespeople are prepared to 
meet any currently advertised price on 
anything we sell (call for details. ..it's Toll 
Free!). We pay shipping and insurance 
charges on prepaid cash orders (with 
destinations in the continental US). We ac- 
cept major credit cards for your conve- 
nience. If the product you receive is defec- 
tive, even up to 30 days after you purchase 
it, we'll repair or replace it and pay for ship- 
ping back to you. 

Consumer Computers carefully selects 
the hardware and software it offers to in- 
sure that quality is maintained in everything 
we sell. Our attention to quality is why we 
can stand behind our policy, because we 
stand behind our products. 

You'll never regret becoming a member of 
our growing customer family. You have our 
word. 



SEC 

Microcomputer 




16K's, 32K's 
AVAILABLE 



CALL FOR 
BEST PRICE 



Introducing the Commodor PET! All thethingsyouneedto 
start computing today are built right in. Things like 18K 
PET BASIC, 9" Green Phosphor Video Monitor, 74 key pro- 
fessional keyboard, numeric keypad, and more. As if this 
weren't enough, the PET comes has a parallel I/O port that 
is just waiting for a printer, and the industry standard 
IEEE-488 bus for expansion. 

40 x 25 Column/Line Video Display 

Integrated 9" Green Phosphor Monitor Standard 

Inverse & Overstrike Characters 

Full Screen editing capability Built-in 

Built-in Parallel I/O Port 

IEEE-488 Bus Interface Capability Standard! 

2 Cassette Ports 

18K ROM BASIC (Version 4.0) 

9 Digit Floating Point Binary Arithmetic 

Sophisticated Disk & Tape Handling Software 
Other PET accessories and equipment available at great 
prices. 




ATARI 800 16K 
CALL FOR BEST PRICE 

Atari 400 w/16K 349 

410 Program Recorder 65 

810 Disk Drive 449 

825 80 col. 7x8 Dot matrix impact printer 699 

822 40 col. Quiet Thermal Printer 349 

850 Interface Module 159 

Atari 16K Ram Module 69 

Axlon Ramcram 32K Module 189 

Asteroids, Missile Comand and Star Raiders 35 ea. 



CALL FOR BEST PRICES 

If you're considering a computer, consider this: 

4 Mhz Z-80A Operation 

80 or 40 column modes STANDARD 
Built-in Centronics printer port 
Full ASCII keyboard with Shift lock 
Real Time Clock STANDARD 
RGB Color Output 
Mixed text and graphics 
Numerica Keyboard STANDARD 
CP/M Compatibility 

5 programmable Function keys 

24K Microsoft N BASIC in ROM with enhanced 
color graphic commands 

The NEC PC-8001A has all these features and much 
more. Expandibility you want, expandability you get. 
Through the use of the PC-8012A I/O unit, total system 
RAM can be extended to 160K. The PC-8031 Dual Disk 
Drive puts 286K of floppy disk storage at your comand. 

The NEC PC-8001A has so many things that are options 
on other computers built right in that you may never have 
to buy another accessory! The quality that the NEC name 
has come to sand for has been built-in, too. 

Compare the competition, and then call Consumer Com- 
puters for the NEC PC-8001. 

NEC COMPATIBLE SOFTWARE 

CP/M Operating system with graphicscontrol CALL 

SUPERCALC Financial & Scientific Modeling (requires 

CP/M) CALL 

WORDSTAR Word Processing System (requires CP/M) 

CALL 

SYSTEMS PLUS Complete Accounting System (requires 

CP/M) CALL 

MICROSOFT BASIC-80(requiresCP/M) CALL 

MICROSOFT FORTRAN-80 {requires CP/M) CALL 

MICROSOFT COBOL-80 (requires CP/M) CALL 




ORDER TOLL-FREE — 800 854 6654 . 



In California and outside Continental U.S. 714-698-8088 



Call for 
Details 



Please refer to ordering instructions on preceding page. 

Circle 127 on inquiry card. 





TIME 



Figure 3: An amplitude-versus-time graph of the sine wave sound produced by listing!. 



JONATHAN WINTERS COULD BE YOUR 
SALESMAN OF THE YEAR. . . 

... if you sell small computers, word processing systems, 
software, media and supplies or computer services. 



COMPUTER 
SHOWCASE 
EXPO 

is coming to these cities in 1982 

March 25-27 • Georgia World Congress Center 

ST, LOUIS 

April 15-17 • A.J. Cervantes Convention Center 
April 15-17 • Commonwealth Pier Exhibition Hall 
Apnr23-25 • Miami Expo/Center 
May 7-9 •Anaheim Convention Center 
September 23-25 • New York Coliseum 
September 30-Octoberl • Brooks Hall 




Because Johnny is our top salesman 

for COMPUTER SHOWCASE EXPO-a new 
concept in end-user computer shows. These 
sales events cater to your most serious 
prospects— small businessmen, doctors, 
lawyers, accountants, educators— and 
personal computerists excited about putting 
computer power to work at home. 

How does Johnny bring in the buyers? 

He is featured in an all out media blitz — 

• Prime Time TV 

• Drive Time Radio 

• High Visibility Newspaper Ads 
•Targeted Direct Mail 

You've never seen an end-user computer 
show promoted like COMPUTER 
SHOWCASE EXPO-because it's never been 
done before. 

And you've never seen buyers at an end- 
user show before like you'll see at 
COMPUTER SHOWCASE EXPO! But don't 
take our word for it. Here's what exhibitors 
said: 

AMERICAN COMPUTER NETWORK— 

"Our average configuration is about 
$42,000. We sold about 20 systems and 
probably have 300 good leads to follow. " 

RADIO SHACK— "100% most successful 
business show we ever attended. " 

ALTOS COMPUTERS-' Very enthusiastic and 
serious buyers. The most professional 
computer show ever produced in San 
Francisco..." 



ctober 28-30 • Miami Expo/Center 

CHICAGO , , 

November 4-6 • McCormick Place 

LOS ANGELES , 

November 18-20 • Los Angeles Convention Center. 



So if you want Jonathan Winters on your sales 
force, write or call today for information on 
COMPUTER SHOWCASE EXPO. 

Call toll-free (800) 225-4620 

Ask for Fred Stern 

(In Massachusetts, (617) 879-4502) 



THE INTERFACE GROUP 

PO Box 927, 160 Speen 5treet, Framingham, MA 01701 

(617) 879-4502, Outside Mass (800) 225-4620 

Producers of 

INTERFACE FEDERAL DP EXPO COMDEX COMDEX/SPRINC 

COMDEX/EUROPE THE COMPUTER SHOWCASE EXPOS. 



In this demonstration program, the 
sound created is a close approxima- 
tion to a sine wave. A graph of the 
waveform is given in figure 3. 

The Role of Sound in Programs 

This article and last month's install- 
ment of "The Atari Tutorial" have 
discussed the technical aspects of 
sound generation with the Atari 400 
and 800 computers. However, the 
programmer must also understand 
the broader role of sound in the com- 
plete software package. 

Moviemakers have long under- 
stood the importance of mood-setting 
background music. The recent Star 
Wars movies by George Lucas are ex- 
cellent examples. When Darth Vader 
enters the room, you immediately 
fear and hate him because of the 
menacing background rhythms ac- 
companying his entry. You know to 
gleefully applaud when Luke 
Skywalker saves Princess Leia 
because gallant music plays in the 
background. Likewise, horror films 
can frighten you merely by playing 
eerie music, even though the action 
may be completely ordinary. 

Tatio America's Space Invaders 
program for the Atari 400/800 issues 
a personal threat to the player with its 
echoing stomp. As the tempo in- 
creases, knuckles whiten and teeth 
grind. When you fire a photon 
torpedo in Atari's Star Raiders game, 
the computer gives you a "launch" 
sound that decreases in frequency as 
the torpedo speeds away from you. 
The effective use of sound can in- 
crease your involvement with a game 
or other program. 

Impressionistic sounds affect our 
subconscious and our state of mind. 
This may be due to the fact that 
sounds, if present, are continuously 
entering our mind whether or not we 
are actively listening. Visual inputs, 
on the other hand, require the user's 
attention. If we are distracted from 
the TV set, we cease to concentrate 
on the picture and the image leaves 
our mind. Sound therefore offers the 
programmer a direct path to the 
users' minds — bypassing their 
thought processes and zeroing in on 
their emotions. ■ 



150 April 1982 © BYTE Publications Inc 



Circle 213 on Inquiry card. 



In this age of runaway inflation. 



Look what $825 will buy 





The ideal input device for the small 
system user. 





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The HIP AD™ digitizer 

Inexpensive input to your computer 

The HIPAD™ digitizer can be used for both converting graphic information into 
digital values and as a menu. Utilizing either the stylus or the optional cursor, the 
operator can input graphic data into the computer by locating individual points on 
the digitizers 11" x 11" (28cm x 28cm) active area. In the "stream mode" a contin- 
uance of placements of coordinate pairs may be input. 

Not a kit, the HIPAD™ comes complete with both RS-232-C and parallel interfaces 
and has its own built-in power source. The origin is completely relocatable so coor- 
dinates may be positive or minus for a true reference value and oversized material 
may by input by simply resetting the origin. 

Accurate positional information, free form sketches, 
even keyboard simulation 

All can be entered using the multi-faceted HIPAD™ digitizer. Its capabilities and 
low price make the UL listed HIPAD™ a natural selection over keyboard entry, inac- 
curate joysticks, or expensive approximating light pens. It's perfect for inputting 
isometric drawings, schematics, X-rays, architectural drawings, business graphs, 
and many other forms of graphic information, as well as creating your own graphics. 

Use it with Apple II™ , TRS-80 Level II ™ , PET ™ or other 
popular computers 

The HIPAD's™ built-in RS-232C and parallel 8 bit interfaces make it all 
possible. (For Apple II order DT-1 1 A, for TRS-80 or PET order DT-11). 
Furthermore, you get English or metric scaling, data format (Binary/BCD/ASCII), 
selectable baud rates, and resolution of either .005" or .01". 

For complete information, contact Houston, Instrument, P.O. Box 15720, Austin, Texas 78761. 
(512) 835-0900. For rush literature requests, outside Texas call toll free 1-800-531-5205. For 
technical information ask for operator #5. In Europe contact Houston Instrument, 
Rochesterlaan 6. 8240Gistel, Belgium. Phone 059/27-74-45. Telex Bausch 81399. 



Available with optional display. 
'U.S. Suggested retail price 



TM HIPAD is a trademark of Houston Instrument 
TRS-80 is a trademark of Tandy Corporation 
APPLE is a trademark of Apple Computer Inc. 
PET is a trademark of Commodore Business Machines. Inc. 

Circle 195 for literature. 

Circle 196 to have representative call. 



INSTRUMENTS & SYSTEMS DIVISION 
Tbgether...\/\/e'll create tornorrrjw. 

BAUSCH & LOMB (▼; 




Introducing 
the Sinclair ZX81 

If you're ever going to buy 
a personal computer, now is the 
time to doit. 

The new Sinclair ZX81 is the 
most powerful, yet easy-to-use 
computer ever offered for anywhere 
near.the price: only $149.95* completely 
assembled. 

Don't let the price fool you. The 
ZX81 has just about everything you 
could ask for in a personal computer. 
A breakthrough 
in personal computers 

The ZX81 is a major advance over 
the original Sinclair ZX80— the world's 
largest selling personal computer and 
the first for under $200. 

In fact, the ZX81's new 8K Extended 
BASIC offers features found only on com- 
puters costing two or three times as much. 

Justlookatwhatyou get: 

■ Continuous display, including moving 
graphics 

■ Multi-dimensional string and numerical 
arrays 

•Plus shipping and handling. Price includes connectors 
for TV and cassette, AC adaptor, and FREE manual. 



■ Mathematical and scientific functions 
accurate to 8 decimal places 

■ Unique one-touch entry of key words 
like PRINT, RUN and LIST 

■ Automatic syntax error detection and 
easy editing 

■ Randomize function useful for both 
games and serious applications 

■ Built-in interface for ZX Printer 

■ 1K of memory expandable to 16K 

The ZX81 is also very convenient 
to use. It hooks up to any television set 
to produce a clear 32-column by 24-line 
display. And you can use a regular 
cassette recorder to store and recall 
programs by name. 



If you already own a ZX80 

The 8K Extended BASIC 
chip used in the ZX81 is available 
as a plug-in replacement for your 
ZX80 for only $39.95, plus shipping 
and handling— complete with new key- 
board overlay and the ZX81 manual. 
So in just a few minutes, with no 
special skills or tools required, you can 
upgrade your ZX80 to have all the 
powerful features of the ZX81. (You'l 
have everything except continuous dis- 
play, but you can still use the PAUSE 
and SCROLL commands to get moving 
graphics.) 

With the 8K BASIC chip, your 
ZX80 will also be equipped to use the 
ZX Printer and Sinclair software. 

Order at no risk** 

We'll give you 10 days to try out 
theZX81. If you're not completely satis- 
fied, just return it to Sinclair Research 
and we'll give you a full refund. 

And if you have a problem with 
your ZX81, send it to Sinclair Research 
within 90 days and we'll repair or replace 
it at no charge. 

**Does not apply to ZX81 kits. 




NEW SOFTWARESinclair has 

published pre-recorded pro- 
grams on cassettes for your 
ZX81, or ZX80 with 8K BASIC. 
We're constantly coming out 
with new programs, so we'll 
send you our latest software 
catalog with your computer. 



ZX PRINTER: The Sinclair ZX 
Printer will work with your ZX81, 
or ZX80 with 8K BASIC. It will 
be available in the near future 
and will cost less than $100. 



16K MEMORY MODULE: 

Like any powerful, full fledged 
computer, theZX8l is expand- 
able. Sinclair's 16K memory 
module plugs right onto the 
back of your ZX81 for ZX80, 
with or without 8K BASIC). 
Cost is $99.95, plus shipping 
and handling. 



ZX81 MANUAL: The ZX81 
comes with a comprehensive 
164-page programming guide 
and operating manual de- 
signed for both beginners and 
experienced computer users. 
A $10.95 value, it's yours free 
with the ZX81. 



99 95 personal comp 



Liter. 



w 



Introducing 
theZX81kit 

If you really want to 
save money, and you enjoy 
building electronic kits, you 
can order the ZX81 in kit form 
for the incredible price of just 
$99.95* It's the same, full-featured 
computer, only you put it together 
yourself. We'll send complete, easy- 
to-follow instructions on how you can 
assemble your ZX81 in just a few hours. 
All you have to supply is the soldering iron.l 

How to order 

Sinclair Research is the world's larg- 
est manufacturer of personal computers. 

The ZX81 represents the latest 
technology in microelectronics, and it 
picks up right where the ZX80 left off. 
Thousands are selling every week. 

We urge you to place your order 
for the new ZX81 today. The sooner you 
order, the sooner you can start enjoying 
your own computer. 

To order, simply call our toll free 
number, and use your MasterCard or VISA. 

CTo order by mail, please use the 
Coupon. And send your check or money 
order. We regret that we cannot accept 
purchase orders or C.O.Dls. 

CALL 800-543-3000. Ask for op- 
erator #509. In Ohio call 800-582-1364. 
In Canada call 513-729-4300. Ask for 
operator #509. Phones open 24 hours 
a day, 7 days a week. Have your Master- 
Card or VISA ready. y 

These numbers are for orders 
only. For information, you must write to 
Sinclair Research Ltd., 2 Sinclair Plaza, 
Nashua, NH 03061. 



~t>J 



inmlair- 



■a? 



&St» 



r 



[AD CODE s v44BY| 



PRICEt QTY. AMOUNT 



ZX81 



ZX81 Kit 



8K BASIC chip (for ZX80) 



; Memory Module (for ZX81 or ZX80) 



Shipping and Handling 



$149.95 



99.95 



39.95 



99.95 



4.95 



TOTAL 



$4.95 



MAIL TO: Sinclair Research Ltd., One Sinclair Plaza, Nashua, NH 03061. 

NAME 

ADDRESS 



'CITY/STATE/ZIP_ 

t U.S. Dollars 





irth- 



H-£§. 




Bison Takes the Bite Out of High Prices 



G 





\ 




f 


N 


Epson Eradication 






Software Scrunch 




EsponMX80 


$405 




dBase II 8" 


$595 


Epson MX 80 FT 


$515 




dBase II 5" 


$540 


Epson MX 100 


$695 




DB Master 


$179 


Epson Graftrax Roms 


$ 74 




Wordstar 8" 


$310 


Epson Replacement Cart 


$ 11 




Wordstars" 


$227 


Interface to Apple 


$ 84 




Spellstar8" 
SpellstarS" 


$189 
$164 


Monitor Munch 






Visicalc 
Visiplot 
Visiterm 


$146 
$145 


Amdek 13" Color Monitor 


$346 




$123 


Amdek Color II RGB Monitor 


$895 




Visitred/Visiplot 


$214 


NEC 12" Green Screen 


$166 




Personal Filing System 


$ 71 


NEC RGB Color Monitor 


$945 




Personal Report System 


$ 71 


Zenith Green Screen 


$134 




Data Capture 4.0 
DataCapture4.0/80 


$ 52 
$ 77 


Peripheral Portion 










D.C. Hayes Micromodem II 


$295 








D.C. Hayes Smartmodem 


$239 




Game Gnaw 




Microsoft RAM Card 


$149 




David's Midnight Magic 


$ 28 


Microsoft Z-80 Card 


$295 




Red Alert 


$ 24 


Paddle Adapple 


$ 24 




Space Eggs 


$ 18 


Smarterm 80 Column Card 


$286 




High Res Soccer 


$ 23 


Thunderclock X-10 Interface 


$ 42 




Gamma Gobblins 


$ 22 


ThunderclockCard 


$116 




Robot Wars 


$ 31 


Tandon Drive TM 848-2 


$475 




Sargon II 


$ 26 


Visidex Videoterm 80 Col 


$277 




Alien Typhoon 


$ 19 


FORTH 79 Fit 






Bug Attack 
Castle Wolfenstein 


$ 24 
$ 25 


Starting FORTH 


$ 14 




Computer Baseball 


$ 31 


FORTH Programming Aids 


$135 




Computer Bismark 


$ 48 


Nautilus System Cross-Compiler 


$179 




Cops and Robbers 


$ 28 


System Guide to Fig-FORTH 


$ 22 




Epoch 


$ 26 


Micromotion FORTH 79 for Apple 


$116 




Phantom Five 


$ 23 


Micromotion FORTH 79 for 280 CPM 


$116 




President-Elect 


$ 31 



ORDER FORM 



Address 
City 
State . . 



Zip 



Visa/MC# .__ 
Expiration Date 
Signature 



Item 



Price 



California res. include 

6% state sales tax 

Total __ 

Send cashier check, money order or charge or- 
der on Visa or Master Card. Please allow 4-6 
weeks for delivery. Shipping C.O.D. based on 
weight. Free shipping on all orders over S500. No 
C.O.D. orders. Prices and availability subject to 
change without notice. Phone orders welcome. 

Mail to: Bison Products 

P.O. Box 9078-184 ■■■■ 
Van Nuys, CA 9 1 409 t*es%s< 

FOR FAST SERVICE CALL 
(213)891-5702 



mmm 



Circle 53 on inquiry card. 



PRODUCTS 

1 6709 Roscoe Boulevard, Sepufveda, C A 91 343 



Book Reviews 



The Mind's I 

Douglas R. Hofstadter 
and Daniel C. Dennett, 
Basic Books Inc., 
New York, 1981. 
501 pages, hardcover 
$15.50 



Reviewed by Lloyd Milligan 
8604 Maywood Dr. 
Columbia, SC 29209 



This book is designed to 
provoke, disturb, and befud- 
dle its readers, to make the 
obvious strange and, per- 
haps, to make the strange 
obvious. 

(from the Preface) 

Most people take consider- 
able pleasure in being aston- 
ished. Witness the popular 
television show That's In- 
credible. For those who are 
less easily astonished, but 
who enjoy a special kind of 
challenge, Douglas R. 
Hofstadter and Daniel C. 
Dennett have "composed and 
arranged" The Mind's I, a 
splendid collection of essays 
on mind and consciousness, 
"self and soul." Each essay 
concludes with a "Reflection" 
based on the editors' own 
thoughts and reactions. 

Of all the pursuits of man, 
science has been the most 
productive. In the present 
century, the so-called neuro- 
sciences (neurobiology, 
neurochemistry, neuropsy- 
chology, etc.) have con- 
tributed significantly to our 
understanding of how the 
human brain works. Para- 
doxically, however, deep 
issues of both historical and 
enduring interest have been 
on the whole ignored by 
these new sciences. The 
denial of mind and con- 
sciousness as valid topics of 
scientific inquiry may be 
traced to the influence of 



logical positivism, opera- 
tionalism, and behaviorism. 
The Mind's I could be said to 
be about those things that be- 
haviorism denies. 

A recurring theme or de- 
vice in many of these essays is 
the "thought experiment." In 
a thought experiment, one 
imagines all the procedures 
and conditions of an experi- 
ment and attempts to imagine 
or deduce what the outcome 
would be. The power of a 
thought experiment — and 
also its weakness — comes 
from imagining procedures 
which cannot be carried out 
in reality. The key to distin- 
guishing whether a thought 
experiment could be realiz- 
able is to decide if the condi- 
tions of the experiment are 
possible "in principle." In 
reading these essays I was 
sometimes reminded of Mark 
Twain's satire on facts and 
miracles: ". . . if it is a 
Miracle, any sort of evidence 
will answer, but if it is a Fact, 
proof is necessary." It is often 
difficult to know whether a 
suggested condition is merely 
technically infeasible or im- 
possible in principle. Fortu- 
nately, Hofstadter and Den- 
nett provide some assistance 
in this regard, but there is still 
a danger — thought experi- 
ments that support your 
point of view will seem more 
likely to be realizable than 
those that oppose it. 

Thus far it may not be ob- 
vious why The Mind's I has 
special interest to computer 
enthusiasts. That it does is 
partly due to a new breed of 
cognitive psychologists — 
called computer scientists — 
whose major research interest 
is artificial intelligence (AI). 
If your concept of AI is based 
on the Eliza program, then 
you probably need to be 
brought up to date. Current 
AI research involves topics 
such as simulating human 



ability to understand stories 
(Roger Schank et al.; dis- 
cussed by John R. Searle in 
"Minds, Brains, and Pro- 
grams," page 353). Such pro- 
jects shed new light on the 
meaning of "understanding," 
and at the same time expose 
the awesome complexity of 
human knowledge database 
design. In one sense, the ulti- 
mate goal of AI research is to 
give objective meaning to 
concepts that have heretofore 
been understood only in the 
subjective sense. 

The brain's hardware, 
which at the very least "sup- 
ports" thought, cannot be ig- 
nored. Several thought ex- 
periments in this book focus 
on the neural-circuit descrip- 
tion of brain functioning. It is 
easy to slip from this focus to 
the assumption that the brain 
is purely a digital machine. 
This assumption is unwar- 
ranted even at the cellular 
level. For example, synapses 
(connections between nerve 
cells) are not strictly analo- 
gous to logic gates. Thou- 
sands of axon terminals may 
impinge upon the dendrites 
of a single cell. The events 
that transpire there (at the 
synapse) are more analog 
than digital in nature. One 
may even speculate that it is 
not possible "in principle" to 
model these processes se- 
quentially in real time. 

While reading these essays 
I found myself formulating 
point-by-point replies. More 
often than not, Hofstadter or 
Dennett expressed my ap- 
proval or misgivings more 
clearly than I could have 
done. Their comments not 
only reflect on the essays 
themselves, but go on to pre- 
sent new variations on re- 
lated themes. The reader is 
compelled to reflect on the re- 
flection, and so on, until in- 
tellectual fatigue sets in. 

A common thread runs 



through this collection, but it 
is not easy to discern. Vari- 
ous conceptions of mind, 
self, and soul are set up, ex- 
posed, scrutinized; the idea is 
to inquire which, if any, of 
these are possible models of 
mind, self, or soul. The mind 
as a program of immense in- 
tricacy, involving deep "level- 
crossing" structures (e.g., 
how can a thought influence 
a synapse?) and Godelian 
loops, is one idea that 
emerges . 

The Mind's I does not ex- 
plain the mind's I. Perhaps it 
aims to describe what such an 
explanation would be like. In 
one reflection, Hofstadter is 
careful to distinguish emula- 
tion of the mind from simula- 
tion. Explanation is at least 
one step further removed. 
And while this book does not 
pretend to "explain" self or 
soul, the impression emerges 
that, with thoughtful consid- 
eration, these problems of the 
ages may be tractable, after 
all. 

At another level, The 
Mind's I expresses a tone of 
personal warmth and enthu- 
siasm. The authors inquire of 
one of Stanislaw Lem's es- 
says, "Is this poetry, philoso- 
phy, or science?" I asked 
myself the same question 
about the book as a whole 
and concluded that it is a 
combination of all three. One 
thing that the book is not is 
hocus pocus. Hofstadter and 
Dennett eschew pseudosci- 
ence. Their views are com- 
pletely compatible with the 
scientific world view. It's just 
that science has not yet made 
deep inroads into the prob- 
lems that make up the main 
focus of this book. Perhaps 
this deficiency will yield in 
part to the union of computer 
science, neuroscience, cogni- 
tive science, philosophy, and 
linguistics. ■ 



April 1982 © BYTE Publications Inc 155 



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A Po(r)tpourri of Ideas 

Fifth in a Series 

Three inexpensive hardware/ software projects to let you use the 
cassette port for a tone generator, telephone dialer, and 

RS-232C output channel. 



William Barden Jr. 

28122 Orsola 

Mission Viejo, CA 92692 



There's always an advantage in 
using existing hardware to interface 
external devices — there's no need to 
perform address decoding, to hook 
up to a multiline bus, or to design and 
implement controller functions. The 
cassette port is the most rudimentary 
input/output port in the TRS-80 
Models I and III. It was originally 
designed to interface to an audio 
cassette recorder so that BASIC and 
machine-language programs and data 
could be saved and loaded. The 
cassette port, however, can be used in 
a variety of other ways. In this arti- 
cle, I'll describe three projects that use 
cassette-port output. 

These projects will work with a 
Model I system without the expan- 
sion interface and with any Model III. 
The projects are a tone generator with 
volume control, a telephone dialer, 
and an RS-232C driver. A fourth use, 
controlling a nuclear fast-breeder 
reactor, was to be included, but still 



About the Author 

William Barden Jr. has written many books 
on microcomputer programming and design. 
He is a member of the Association for Com- 
puting Machinery and the Institute of Electrical 
and Electronics Engineers. 



needs a little polishing up. Perhaps in 
a later article . . . 



Cassette Logic 

The TRS-80 Models I and III use 
similar logic in the cassette output, as 
shown in figure 1. The REMote out- 



put to turn on the recorder is slightly 
different in address decoding between 
the Models I and III, but in both cases 
it simply closes a relay. Two normal- 
ly open relay contacts go to pins 1 
and 3 of the cassette jack, a 5-pin DIN 
connector. The relay output won't be 
used for these projects, since some of 




-O CASSOUT 



>12K 



>7.5K 



+ 5V 



220K 



NORMALLY 
OPEN 



TO 

"MOTOR ON' 

LOGIC 



,1— L 




^> 



TO "REMOTE" 

PLUG 



RELAY 



JT 



-O GND 



REM 



FRONT 
VIEW 



4o3 ioA 1 



SF 



Figure 1: Model l/III cassette output is performed by a two-bit latch that generates 
three voltage levels. The three voltage levels can produce a square wave with a positive- 
going pulse, a negative- going pulse, and a zero level. A motor relay connects two nor- 
mally open contacts. 



158 April 1982 © BYTE Publications Inc 



Port OFF Hexadecimal 
Bit 1 BitO 



CASSOUT Voltage (V) 

= 
= 0.4 
= 0.8 
= 0.4 



Table 1: CASSOUT voltages. The two latch bits produce four voltage levels. The 11 
configuration is redundant and is not used. 




DATA PULSE IF "l" 
OTHERWISE 00 
LEVEL 



+.8V 
+.4V 



1 MILLISECOND 



-2 MILLISECONDS BIT TIME- 
( 500 BITS /SECOND) 



Figure 2: The recording technique for 500 bps uses a clock pulse spaced at 2-ms inter- 
vals. A data pulse at the midpoint between clock pulses represents a 1; the absence of a 
data pulse represents a 0. 



CASSOUT E> 



+ 4 TO+12V 

4 



^ 



MINIATURE 
POTENTIOMETER 




Figure 3: In the TONOUT electronics, an LM386 audio-amplifier chip is driven by the 
CASSOUT signal. The output of the LM386 drives a small speaker. 



the earlier relays were prone to "stick- 
ing" (especially when used to control 
the AC supply for milling machines). 
Instead, what will be used is the 
output that normally goes to the 
AUXiliary input of the cassette 
recorder to write data on the tape. 
This is a single line connected to pin 5 
(CASSOUT) of the DIN connector. 
This line is driven by two bits at I/O 
address OFF hexadecimal in both the 
Models I and III. 



Three voltage levels can be output 
to the CASSOUT line, depending 
upon the configuration of the two 
least significant bits of port OFF hexa- 
decimal (see table 1). A bit configura- 
tion of 01 binary produces about 
volts (V), 00 produces about 0.4 V, 
and 10 produces about 0.8 V. Bit con- 
figuration 11 is redundant as it 
generates 0.4 V again. 

The three voltage levels are used to 
write data onto the cassette in the 



500-bits-per-second (bps) mode, as 
shown in figure 2. A single square- 
wave cycle is first generated to pro- 
duce a clock pulse. Then, either 
another cycle is output, representing 
a 1 data bit, or no cycle is output, 
representing a data bit. 

The Model III also has 1500-bps 
capability. In this mode, continuous 
frequency-shift keying is used, with 
1320-hertz (Hz) and 2680-Hz tones 
representing the data. Only the 0- and 
0.8-V levels are used for this scheme. 

In both cases, the major part of the 
logic is in the ROM (read-only 
memory) firmware. The electronics 
really just consist of the two output 
latches and a few resistors. 

In the following projects, I'll use 
the two bits of port OFF hexadecimal 
to generate square waves for musical 
tones, telephone dialing, and RS- 
232C output. The greater part of the 
design effort, as in the TRS-80 
cassette functions, is in the software. 
The hardware will consist of three 
simple circuits with a minimum of 
parts. 

(A note about connectors: For con- 
necting all three projects to your 
TRS-80 cassette port, use a standard, 
thin-walled, 5-pin DIN plug, such as 
Radio Shack's catalog item 274-003.) 



A Musical Tone Generator 

Our first project produces six oc- 
taves of notes representing the first 
six octaves on the piano keyboard. 
The notes are square waves, rich in 
odd-order harmonics. Two volume 
levels can be output, one using the 
0- and 0.4-V levels, and a second 
using the 0- and 0.8-V levels. 

The circuit shown in figure 3 uses 
the CASSOUT output as an input to 
an LM386 audio amplifier. The 
LM386 requires only a capacitor and 
8-ohm (Q) speaker to implement a 
complete audio amplifier. A minia- 
ture 10-kfi potentiometer is used at 
the input for volume control. The 
power supply for the LM386 can be 
any convenient voltage from +4 to 
+ 12 V. A 6-V battery works fine for 
the power supply, or you can obtain 
a low-priced power-supply kit from 
Radio Shack. 

TONOUT (listing 1) is an assem- 



April 1982 © BYTE Publications Inc 159 



Circle 263 on inquiry card. 



vsSSfc 



YoW 



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memo r ^° resS lines- 



me h address"" - 
Buffere te power ^PP ly ' 

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-nn-227-1 61 ' oR .- 



write us ^ 



Box 1140 

2000 Center St., 

Berkeley, 

CA 94704. 



developments 



Listing 1: TONOUTis a Z80 subroutine to output tones through the cassette port. The 
code is to be embedded in the BASIC program of listing 3. 



91300 




00100 




ORG 


9000H 








t)0 1 1 


; >:■-*>:■>:■*>: 


#*■ •****•!» 


«•*•***********■* 


* >:• * * * * * * * * >:■ * * * # * * * * * * * * * ■*■ * >:■ * >:• 






00120 


!* TONE 


OUTFIT 


'. OUTPUTS TONE 


THROUGH CASSETTE PORT. * 






00130 


* * 


ENTRY: 


hl=o- parameter 


BLOCK * 






00 1 40 


; a 




FARAM+0-DURATI 


UN CNT IN 2 BYTES * 






MEU50 


; * 




+ 2 = F R E Q CN T * ( 1 8 . 4 MICROS E C S M D I * 






00151 


7 * 




15.79 


MICROS ECS MOD III), 2 BYTES * 






00 1 60 


* * 




+4-LEVEL : 


2*4..0Wi3~HIGH, ONE BYTE * 






00170 


' * 


e::x I T : 


AFTER TONE HAS 


SOUNDED * 






00180 


; **•>:>:*■* 


>:•>:•*>:•>:■*■ 


• >:■ * •*• * >: >:• • >>:• * >:■ « >:■ * * •►: 


* * * >:• * * * * * * * * * * * * * * * * * * * * * * * * * 






00190 










9000 


CD7F0A 


00200 


TONOUT 


CALL 


0A7FH 


;GET HL 


9003 


e-5 


002 1 




PUSH 


HI... 


; TRANSFER TO IX 


9004 


DDEl 


00220 




POP 


IX 




9006 


DD4E04 


00230 




ID 


C» < IX-t-4) 


; PUT LEVEL. IN C 


9009 


DD6603 


00:240 




L D 


Hi (IX +3) 


; MSB FREQUENCY 


900 C 


DD6E02 


002': 50 




LD 


Li (IX+2) 


?LBB FREiWUENCY 


900F 


7C 


00260 




LD 


A i H 


;GET MSB FREQ CNT 


9010 


B7 


00270 




OR 


A 


5TEST FOR ZERO 


901 1 


2022 


00280 




JR 


N2 i LOWFRE 


5GO IF LOW FREQUENCY 






810290 


3 H I GH 


FREQUENCY HERE 




90 1 3 


45 


00300 




LD 


B i L 


;GET FREQUENCY COUNT 


9014 


DD6601 


00310 




LD 


H i (IX ■!■■ 1 ) 


;MSB OF DURATION 


9017 


DD6E00 


00320 




LD 


Li < IX+0) 


U..SB OF DURATION 


901 A 


2B 


m:zm 




DEC 


HI- 


J FOR JR NC 


90 IB 


i 1. FFFF 


00340 




LD 


DE i - 1 


;FOR FREQ LOOP 


90 1 E 


79 


00350 


H 1010 


LD 


Ai C 


; LEVEL TO A (4) 


90 IF 


EE02 


00360 




XOR 


2 


SNOW OR 01 (7) 


9021 


03FF 


00370 




OUT 


( 0FFH ) 1 A 


;TURN ON ( 11 ) 


9023 


7'B 


00380 




LD 


A»B 


;GET FREQ COUNT (4) 


9024 


3D 


00390 


HI 020 


DEC 


A 


1ON LOOP (4) 


9025 


20FD 


00400 




JR 


NZ5HI020 


;LOOP TIL (12/7) 


902/ 


79 


00410 




LD 


Ai C 


•DUMMY (4) 


902B 


3EW2 


00420 




LD 


A, 2 


; NOW 1 ( 7 ) 


902A 


D3FF 


00430 




OUT 


( 0FFH ) 1 A 


;TURN OFF (11) 


90 2 C 


78 


00440 




LD 


A»B 


J GET FREQ COUNT (4) 


902D 


3D 


0045CM 


I-II030 


DEC 


A 


; OFF LOOP (4) 


90 2 E 


20 FD 


00460 




JR 


NZiHI030 


;LOOP TIL. ( 12/7) 


9030 


19 


00470 




ADD 


Hl_i DE 


; DECREMENT DUR CNT (11) 


9031 


38EB 


00480 




JR 


Ci HI 010 


;GO IF NOT (12/7) 


9033 


1 £323 


00490 




JR 


LOW090 


; RETURN TO BABIC 






00500 


S LOW FREQUENCY HERE 




903.':) 


E5 


005 1 


LOWFRE 


PUSH 


HI- 


i FREQ COUNT TO DE 


90136 


Dl 


00520 




POP 


DE 




9037 


CPM3 


00530 




RES 


0i E 


;MAKE EVIMN 


9039 


DD46O0 


'00540 




LD 


B* < IX+0) 


; DURATION CNT TO B 


903C 


79 


00550 


LOW010 


LD 


A 1 C 


;GET LEVEL (4) 


903D 


EE02 


00560 




XOR 


2 


SNOW OR 01 (7) 


903F 


D3FF 


00570 




our 


( 0FFH ) 1 A 


;TURN ON (11 ) 


904 1 


62 


00580 




LD 


H 1 D 


;GET FREQ COUNT (4) 


9042 


6B 


00590 




LD 


L. > E 


; ( 4 ) 


9043 


2E'. 


00600 


L.OW020 


DEC 


HL 


5DECR FREQ CNT (6) 


9l'Vi4 


2B 


006 1 




DEC 


HL 


J (6) 


904?) 


7C 


00620 




LD 


A 1 H 


;TEST HL. (4) 


9046 


BS 


00630 




OR 


L 


? ( 4 ) 


9047 


20FA 


00640 




JR 


NZiLOW020 


;GO IF NOT (12/7) 


9049 


79 


006! r 70 




LD 


Ai C 


; DUMMY (4) 


904 A 


3E02! 


00660 




LD 


A>2 


?NOW 10 (7) 


904C 


D3F r F 


00670 




OUT 


( 0FFH ) , A 


; TURN OFF ( 1 1 ) 


90 4 E 


62 


00680 




LD 


H 1 D 


;GET FREQ COUNT (4 ) 


904F 


6B 


0(3690 




LD 


LiE 


; ( 4 ) 


9050 


2B 


00700 


LOW030 


DEC 


HL 


;DECR FREQ CNT (6) 


90*5 1 


2B 


00710 




DEC 


HL 


; (6) 


9052 


7C 


00720 




LD 


A 1 H 


;TEST HL (A ) 


9053 


B5 


003730 




OR 


L 


• ( 4 ) 


9054 


20FA 


00740- 




JR 


NZ , LOW 030 


;GO IF NOT (5 2/7) 


9056 


10E4 


00750 




I3JNZ 


LOW01.0 


;GO l\' : D CNT NOT (13/ 


9058 


C9 


00760 


LOW090 


RET 




iREIUFW TO BA8.TC 


0000 




00770 




END 







bly-language program that drives the 
circuit to produce square waves from 
about 20 Hz to over 10,000 Hz. The 
extreme low and high frequencies 
won't come out very well (if at all) in 
the LM386, but for the middle range, 
tones sound fine. If you're a purist, 
you might consider using CASSOUT 
as an input to an amplifier with better 
fidelity. 



TONOUT is designed to interface 
to a BASIC program. It is completely 
relocatable (more about that later) 
and requires three parameters from 
the BASIC code — a frequency count, 
a duration count, and a level. 

The frequency count is a value 
from 1 to 65,535 that is used to con- 
trol a timing loop. Each count causes 
a delay of 18.04 microseconds (/xs) for 



160 April 1982 © BYTE Publications Inc 



Circle 406 on inquiry card. 



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-"ON" STATE = 
18.04 X COUNT* MICROSECONDS 



01 



00 — 



10 — 



* MODEL 1 



-"OFF" STATE = 
18.04 X COUNT* MICROSECONDS 



-I 



PERIOD = 36.08 X COUNT' 
FREQUENCY = 1 /PERIOD 



MICROSECONDS 



Figure 4: A timing loop turns on the CA5SOUT signal and then turns it off. The same 
frequency count is used for both the on and off delays; hence, the period of the tone is 
twice the delay time. 



A = USR(B) 

B POINTS TO^ 




PARAMETER BLOCK +0* 
+ 1 


DURATION 

COUNT 

1-65,535 


+ 2 

+ 3 


FREQ 

COUNT 

1-65,535 


+ 4 


LEVEL: 2 OR 3 



" )Z80 FORMAT LSB, MSB 



-" )Z80 FORMAT LSB, MSB 



Figure 5: Three parameters are used to interface to TONOUT from BASIC. A duration 
count is held in two bytes, a frequency count in two bytes, and a level in one byte. The 
counts are in standard Z80 address format: least significant byte followed by most 
significant byte. 



the Model I (15.79 for the Model III) 
on the "on" and "off" portions of the 
square wave, as shown in figure 4. 
Therefore, the frequencies of the 
square waves produced are 
1/(36. 08E-6) and 1/(31. 58E-6), 
respectively. 

The duration count of 1 to 65,535 
determines the length of time the tone 
is played. In fact, the duration count 
is the number of cycles of the tone. 
Thus, the length of time the tone 
plays is dependent upon the tone's 
frequency. To play a "quarter note," 
the duration count would be 25 for a 
100-Hz tone, 50 for 200-Hz, and so 
forth. The duration count is 1 /fre- 
quency times the fraction of a second 
the tone is to be played. 

The third parameter is volume 
level. A value of 2 is low and 3 is 
high. The level parameter is in one 
byte. 

The main problem in TONOUT is 
how to get the "tightest" possible loop 



to toggle port hexadecimal OFF bits on 
and off and still allow for low- 
frequency notes with a longer dura- 
tion. The approach used here is to 
split TONOUT into two segments of 
code, one for high-frequency notes, 
and one for low-frequency notes. 

TONOUT is entered from BASIC 
by a DEFUSR call. The CALL 0A7FH 
gets the argument from BASIC and 
puts it into the HL register pair. The 
argument in this case is a pointer to a 
parameter block of the three 
arguments in 7 bytes (see figure 5). 
This pointer is transferred to the IX 
register. 

The level parameter is put into the 
C register and the frequency count is 
put into HL. Next, the frequency 
count is tested for magnitude. If the H 
register is nonzero, the frequency 
count is greater than 255, and a low- 
frequency note is played. 

If the frequency count is less than 
256, the high-frequency segment is 



executed. The single byte of the fre- 
quency count is transferred to the B 
register. Also, the two bytes of the 
duration count are transferred to HL 
and decremented by one for the JR C 
loop. (C will decrement below 
before the loop is terminated.) The 
DE register pair is loaded with —1 for 
a "tight" timing loop. 

The output portion of the loop con- 
sists of two almost identical seg- 
ments. Lines 350 through 400 are the 
"on" portion that turns on the "top" 
of the square wave. Lines 410 through 
460 turn off the output. Both portions 
decrement the frequency count in a 
timing loop that determines the fre- 
quency. The voltage level for the 
"on" portion is determined by 
performing an XOR of binary 10 and 
the level parameter to produce either 
a 00 (low) or 01 (high). 

After one complete cycle, the dura- 
tion count in HL is decremented by an 
ADD HL,DE. If the result is not 
negative, another cycle is generated. 

The code from line 510 through the 
end is a similar routine for low- 
frequency notes. In this case, the fre- 
quency count is held in HL and 
decremented twice. The frequency 
count is first made even by a RES 
instruction for a test of decrementing 
down to zero. The duration count is 
assumed to be 254 or less and is held 
in B for a DJNZ instruction. 

Using TONOUT with BASIC 

TONOUT can be used to generate 
tones other than musical notes. The 
precise frequencies generated are: 

l/((42.49 + 18.04 X count) X 10" 6 ) 

for high-frequency tones and: 

1/((41.15 + 18.04 X count) X 10" 6 ) 

for low-frequency tones. These for- 
mulas are for the Model I. Use 
(37 + 15.79 X count) and (36 + 
15.79 X count) for the Model III. 
The 18.04 (or 15.79) represents the 
on/ off loop times; the other constants 
represent the "overhead" for the fre- 
quency and duration timing. 

BASIC can easily be used to build 
up a table of values for matching fre- 
quency counts to musical notes. 



162 April 1982 © BYTE Publications Inc 



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Listing 2: A BASIC program to generate frequency-delay values that, when input to the 
TON OUT routine, will reproduce tones in standard pitch. Results are shown in table 2. 



20 


PROGRAM TO FIND 


BEST 


FIT 


FOR 


8 OCTAVES 


40 DIM NT$( 11) 










6C3 A*- "A AttB C C#D 


D#E F 


FttG 


Gtt" 




80 


-OR J«0 TO 11 










100 


NT*< J)-MID*(A*i 


J* 2+1 , 


2) 






120 


NEXT J 










140 


FOR I -CD TO 7 










160 


RESTORE 










180 


LP R I NT "OCTAVE 


" ; l + 1 








200 


FOR J"0 TO 1.1 










220 


LPRINT NT*< J) ? " 


-•• • 








240 


N«(27.5*2t I)*2t< (J) /] 


2) : 


LPRINTIMi 


260 


CT-( ( 1/N)-36.5E 


-6 )/\l 


■ . 79 


E-6 




280 


LPRINT "F CNT"" 


; CT 








3(30 


NEXT J 










320 


NEXT I 











OCTAVE 1 


A = 27.5 


FCNT= 2300.64 


A# = 29.1352 


FCNT= 2171.39 


B = 30.8677 


FCNT= 2049.39 


C = 32.7032 


FCNT= 1934.23 


C# = 34.6478 


FCNT= 1825.54 


D = 36.7081 


FCNT= 1722.95 


D# = 38.8909 


FCNT= 1626.12 


E = 41.2035 


FCNT= 1534.73 


F = 43.6535 


FCNT= 1448.46 


F# = 46.2493 


FCNT= 1367.03 


G = 48.9994 


FCNT= 1290.18 


G# = 51.9131 


FCNT= 1217.64 


Table 2: Calculating counts for musical 


notes. A short BASIC program can match 


TONOUT frequency counts with standard pitch values. Here are the results. 



OCTAVE 


MODEL I 


1 
2 
3 
4 
5 
6 


2013,1900,1793,1692,1597,1508,1423,1343,1268,1196,1129,1065 

1005,949,896,845,798,753,710,670,632,597,563,532 

502,473,447,421,398,375,345,334,315,297,280,265 

250,235,222,210,198,186,176,166,154,147,139,131 

124,117,110,104,98,92,87,82,77,73,68,64 

61,57,54,51,48,45,42,40,37,35,33,31 


OCTAVE 


MODEL III 


1 
2 

3 
4 
5 
6 


2300,2171,2049,1934,1826,1723,1626,1535,1448,1367,1290,1218 

1149,1085,1024,966,912,860,812,766,723,682,644,608 

573,541,511,482,455,429,405,382,360,340,321,303 

286,269,254,240,226,213,201,190,179,169,159,150 

142,134,126,119,112,106,99,94,88,83,78,74 

70,66,62,58,55,52,49,46,43,40,38,36 


Table 3: Frequency counts for standard pitch. Six octaves of note values are 


represented by the values in the table. Models I and HI use slightly different values 
because of the difference in clock rates. 



164 April 1982 © BYTE Publications Inc 



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Listing 3: The BASIC program to demonstrate tone generation with the Model I/III 
cassette port. The DATA statements contain the machine-language codes of the 
TONOUT subroutine. 



•'( pi 

VI 
52 



TON' 
1 2 7 i 



I. (3 1 



rem SAMPLE 

DATA 20':-m 

DATA J 02* 3, 

DATA 22 it LftSS 
S3 DATA I2:u 23 H, 2h 
' : ;i4 DATA 62 » 2» 2 Hi ' 
'■i.5 DATA 235 1 24 » 3":i » 
'Lib DATA 12 1.5 238 j 2i 
SV DATA 181 » 325 250 1 
':::.B DATA 43. 43, 12A< 
60 FOR ]-"36t<64~6 r /536 
62 READ A: POKE I» A 
64 NEK"! I 

100 DEEUGR0^H9M00 
1 10 INPUT DiFiL 
j ?0 POKE &HA0W1 * J. NT-; D/2! 
K.30 POKE" &HA003* TNT(E/2 
J 40 POKE &HA004iL 
L5PI A*UBR0(&PIA000) 
1 60 GOTO 1 1 



DRIVER 

229 v :„ 
110, 2 > 
221 i II 
2 1 J j 2f 
"V : :h 12 li 
229 5 2t 
211. 2 l : 
121, c 
1.81s 3", 
10 369! 



61 « 

1 3 J • 
1 7 - 

:i l • ; 

1. 6 s . 



&HA0CJ01 

&HAC9S2) 



70 j 

3 : T « 



,'0* 

> 1 .' •> 

i I 07' 



( ] NT i ) I 
( I Ml (I 

















® 


-© 

-0 
-€ 
-© 
-© 

-e 
-e 
-© 
-© 
-© 


© 




( 
( 
< 
< 

( 
c 
c 
( 
( 

( 
( 
< 
c 
( 

( 
( 
< 
< 






> 

> 
> 

) | 
> ! 
> 

> 

) 
) 








































-© 










-e 

-© 
-© 
-© 
-© 
-e 
-© 
-e 

-0 

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© 


© 













Figure 6: Radio Shack's Experimenter Socket project board uses a matrix of holes into 
which component leads can be plugged. The holes are organized into 46 sets of five plus 
two buses. 



Listing 2 shows a Model III BASIC 
program for converting to standard 
pitch (A = 440 Hz). (The Model I 
version is identical except for the con- 
stants.) This scheme has 12 notes per 
octave: A, A# (A sharp), B, C, C#, D, 
D#, E, F, F#, G, and G#, each 
calculated by raising 2 to successive 
one-twelfth powers. The notes of 
each octave double in frequency over 
the preceding octave. 

The first portion of output from the 
program of listing 2 is shown in table 
2. Table 3 shows suggested integer 
counts for the notes for the Models I 
and III. 

Listing 3 shows the TONOUT pro- 
gram incorporated into a BASIC pro- 
gram as DATA values. The DATA 
values are the machine-language 
bytes of TONOUT. TONOUT is 
relocatable and can be moved 
anywhere in RAM (random-access 
read/write memory). The program in 
listing 3 moves the bytes to 9000 
hexadecimal by a series of POKEs. It 
then INPUTs a duration count, fre- 
quency count, and level value for ex- 
perimentation. 

Constructing the Electronics 

All three projects in this article use 
a similar construction method. Radio 
Shack carries an Experimenter Socket 
project board, which is a matrix of 23 
rows, each with two halves, as shown 
in figure 6. Each of the 46 row 
segments is connected electrically. 
Two buses run down the board on the 
extreme right and left. 

Components can be plugged into 
the board with a minimum of fuss. 
The interconnections for the 
TONOUT electronics are shown in 
figure 7, along with the power sup- 
ply, speaker, and cassette plug con- 
nections. Make the connections to the 
5-pin DIN plug, as shown in figure 8. 

To get precise frequencies for 
TONOUT, it's a good idea to disable 
the real-time clock interrupts in the 
Models I and III. If the real-time clock 
is running (and it may be, even 
without a display), the timing on 
tones may be off by 4 percent, and 
there may be some modulation on the 
tone. Add a disable interrupt (DI) in- 
struction (243 decimal) at the begin- 
ning of TONOUT and an enable in- 



166 April 1982 © BYTE Publications Inc 



Circle 254 on inquiry card. 




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VT18X Computing option 2400 

VT101 DECscope 1215 

VT131 DECscope 1785 

VT132 DECscope 1995 

ADM 3A (dumb terminal) 595 

ADM 5 (dumb with visual attributes) . 645 

ADM 31 (two page buffer) 1095 

ADM 21, 24, 32, 36, 42 

Hazeltine Esprit 645 

Hazeltine Executive 80 Model 20 1495 

Hazeltine Executive 80 Model 30 1715 

1410 (Hazeltine dumb terminal) 575 

1421 (Consul 580 & ADM 3A comp.). 595 

1500 (dumb terminal) 825 

1 520 (buffered, printer port) 1 1 05 

RETRO-GRAPHICS TERMINALS 

VT100 with graphics pkg 3250 

VT125 (DEC graphics) 3280 

ADM 3A with graphics pkg 1795 

ADM 5 with graphics pkg 1845 

300 BAUD TELEPRINTERS 

LA 34-DA DECwriter IV 1045 

LA 34-AA DECwriter IV 1095 

LA 36 DECwriter II 1095 

Diablo 630 RO 2295 

Diablo 630 KSR 2695 

Diablo 1650 KSR 2635 

Tl 743 (portable) 1190 

Tl 745 (port/built-in coupler) 1485 

Tl 765 (port/bubble/b.i. coupler) 2595 

600 BAUD TELEPRINTERS 

Epson MX-80 645 

Tl 825 KSR impact 1570 

Tl 825 KSR pkg 1795 

1200 BAUD TELEPRINTERS 

Epson MX-100 995 

LA 120 RA (receive only) 2095 

LA 120 AA DECwriter III 2295 

Tl 783 (portable) 1645 

Tl 785 (port/built-in coupler) 2270 

Tl 787 (port/internal modem) 2595 

Tl 810 RO impact 1545 

Tl 81 RO pkg 1795 

Tl 820 RO impact 1850 

Tl 820 RO pkg 2025 

Tl 820 KSR impact 2025 

Tl 820 KSR pkg 2195 

Lear Siegler 310 ballistic 1945 

2400 BAUD 

Dataproducts M200 (2400 baud) 2910 

DATAPRODUCTS LINE PRINTERS 

B300 (300 LPM band) 5455 

B600 (600 LPM band) 6930 

B1000 (1000 LPM band) 11330 

BP1500 (1500 LPM band) 19700 

ACOUSTIC COUPLERS 

A/J A242-A (300 baud orig.) 242 

A/J 247 (300 baud orig.) 315 

Vadic VA 3413 (300/1200 orig.) 845 

Vadic VA 3434 (1 200 baud orig.) 845 

MODEMS 

GDC 103A3 (300 baud Bell) 395 

GDC 202S/T (1200 baud Bell) 565 

VA 3212 (Bell 212A comp.) 825 

VA 103 (300baud modemphone) 235 

VA 3451 (orig/ans triple modem) 885 

VA 3455 ( 1 200 baud orig/ans.) 770 

VA 2450 (Bell 201 comp.) 725 

CASSETTE STORAGE SYSTEMS 

Techtran 816 (store/forward) 735 

Techtran 817 (store/for/speed up) 915 

Techtran 818 (editing) „ 1225 

Techtran 822 (dual) 1640 

FLOPPY DISK SYSTEMS 

Techtran 950 (store/forward) 1395 

Techtran 951 (editing) 1995 

•Please call for quote. 



mti 



Distributors, New York, New Jersey and Ohio. 

NewYork: 

516/482-3500, 212/895-7177. 518/449-5959 

Outside N.Y.S.: 800/645-8016 

New Jersey. 201/227-5552 

Ohio: 216/464-6688 

^. * 

170 April 1982 © BYTE Publications Inc 



TO 

CASSETTE PLUG 




RADIO SHACK 
276-175 
EXPERIMENTER 
SOCKET 



WIRING DIAGRAM 
(SEE FIGURE 6) 



I I 



O 

o 

o 
o 
o 
o 
o 

o 
o 
o 
o 
o 



0^8 

o 
o 
o 
o 
o 
o 
o 
o 
o 
o 
o 
o 



o 
o 
o 
o 
o 

o 
o 
o 
o 
o 



© 



Figure 7: The TONOUT circuit is mounted on a project board. It uses three com- 
ponents. The 20-H2 potentiometer can be adjusted for a comfortable volume. 



terrupt (EI) instruction (251 decimal) 
right before the 201 decimal for the 
RET; modify the POKE loop accord- 
ingly. The DI and EI were omitted 
from TONOUT to give the user some 
flexibility in using the project in dif- 
ferent configurations. 



A Telephone Dialer 

Our second cassette-output project 
is a pulse-type telephone dialer 
(TELDIL). Most telephone lines, even 
those using tone dialing, will accept 
dialing by a series of break/make 
pulses, spaced at defined inter- 
vals — similar to those created by a 
rotary-dial telephone. See figure 9 for 
an illustration of pulse dialing. 

The circuit for TELDIL is shown in 
figure 10. Put simply, the circuit 
opens and closes a relay to generate 




USE SHIELDED WIRE 
(GROUND IS SHIELD) 
PREFERABLY 



GROUND LEAD 
CASS0UT LEAD 



Figure 8: Two wires are connected to the 
5-pin DIN plug for the cassette port. 
Shielded wire is preferable, but any wire 
will suffice. 



pulses, which are then transmitted to 
the telephone line through a special 
Data Access Arrangement (DAA) re- 
quired by and available from the 
telephone company. The TELDIL 

Circle 310 on Inquiry card. » 




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• Skip-over-Perf 

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• variable Line Length 

• Text Screen Dump. 

The Grappler™ works with Pascal 
and CPM. 



ff- 



•i 



MAKE 
BREAK 



4 PULSES 
REPRESENT 
DIGIT "4" 



Figure 9: Standard rotary dialing outputs a series of evenly spaced pulses to represent 
the digits through 9. 



CASSOUT 



RADIO SHACK 
MINI RELAY 
(275-004) 




FROM 

TELEPHONE 
DATA ACCESS 
ARRANGEMENT 



Figure 10: The telephone-dialing circuit uses an operational amplifier to trigger a small 
relay. The relay opens and closes the telephone line through the Data Access Arrange- 
ment to simulate a rotary-dial pulse. 



"INTERDIGIT" 
DELAY OF 
830 ms~ 




11 MAKE 



BREAK 



-I 



-I 



t 



61.5 ms 



100 ms/PULSE 
(10 PULSES/sec) 



Figure 11: TELDIL breaks the circuit for 38.5 ms. Pulses are spaced at 100-ms intervals, 
representing 10 pulses per second. An interdigit delay of 830 ms separates the pulse 
trains for each digit. 



B=VARPTR (A$) 










B POINTS TO — _^^ 


LENGTH 




USRO (B) f\ 
POINTS [ I 




LOCATION 
OF A$ 




- ) Z80 ADDRESS FORMAT 
J LSB,MSB 


™ \ 










N 


49 io 


DIGIT = 1 




50 10 


DIGIT = 2 




s 






V 




49 10 


DIGIT = 1 




54 10 


DIGIT = 6 







TERMINATOR IS NOT ASCII 



Figure 12: BASIC passes a pointer to TELDIL. The pointer references a list of ASCII 
digits representing decimal values; the list is terminated by any non-ASCII value, e.g., 
binary 0. 



relay is driven by an LM3900 opera- 
tional amplifier (op amp), which in 
turn is driven by the TRS-80's 
CASSOUT line. 

Whenever the CASSOUT output 
level is greater than or less than V, 
enough current flows through the 
220-ft resistor to turn on the LM3900, 
bringing the output on pin 5 to V. 
This closes the relay and breaks the 
connection to the DAA. The diode 
(Radio Shack's lN4000-series diode, 
catalog number 276-1102) across the 
relay coil is necessary to prevent 
high-voltage "spikes' 7 from the induc- 
tive load of the relay coil from 
damaging the LM3900. 

The software for TELDIL is also a 
relocatable assembly-language pro- 
gram that interfaces to BASIC (see 
listing 4). Although the version 
shown here uses a delay loop for the 
Model I, there is enough "leeway" in 
the constants to use the same code for 
the Model III as well. The 
"make/break" rate for digits is 
limited to 10 pulses per second for 
most telephone systems. The circuit is 
broken for about 38.5 milliseconds 
(ms) for each pulse, and then made 
for 61.5 ms, as shown in figure 11. In- 
terdigit delay is about 830 ms. These 
delays can be adjusted for faster dial- 
ing on an experimental basis. 

BASIC passes a pointer to TELDIL 
in the USR call. The pointer 
references a string of ASCII decimal 
digits, such as "17145551212." Any 
number of digits can be used. The last 
byte of the string is a non-ASCII 
digit, such as binary (see figure 12). 

TELDIL uses two loops. The outer 
loop from lines 250 through 480 picks 
up the ASCII digit from the string, 
tests it for valid ASCII decimal codes 
of through 9, converts the digit into 
a stream of 1 through 10 pulses on the 
line, and increments the string 
pointer. It also delays 830 ms for the 
interdigit delay. 

The inner loop at lines 330 through 
430 pulses the line for each digit. The 
line is broken by outputting binary 01 
to port OFF hexadecimal and then 
delaying 38.5 ms. The line is then 
reconnected for 61.5 ms. The number 
of pulses is held in the B register, and 
the DJNZ repeats the loop for the 
number of pulses required. 



172 April 1982 © BYTE Publications Inc 






BEAUTIFUL PROGRAMMING 













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3C MEMDISK, BMATE, R80, STRLIB and EASYPAK are trademarks of 

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Cache BIOS, SWAT and Pascal-Z are trademarks of Ithaca InterSystems, Inc. 



Computer Company 

DIVISION OF SEA DATA CORPORATION 
ONE BRIDGE STREET NEWTON, MASS. 02158 U.S.A. 

Circle 59 on Inquiry card. 



Listing 4: TELDIL is a Z80 subroutine to simulate a rotary telephone dialer. 



9w;10 



0604 
099C 
7814 
9000 
9003 
9004 
9006 
9009 
900B 
900D 
900F 
9011 
9013 
9015 
9016 
9018 
901A 
901D 
901F 
9021 
9023 
9025 
9028 
902A 
902 C 
902E 
9031 
9033 
9035 
9037 
9039 

903A 
9 GOB 
903D 
903F 
9040 
9041 
9043 
9045 
9047 
9049 
90 4 B 
0000 



CD7F0A 

E5 

DDE1 

DD7E00 

D630 

2002 

3E0A 

3828 

FE08 

3024 

47 

3E01 

D3FF 

210406 

0E00 

1819 

3E02 

D3FF 

219C09 

0E01 

180E 

10E8 

2 1 1 478 

BE 02 

1805 

DD23 

18CD 

C9 

2B 

ED5F 

ED5F 

7C 

B5 

20F7 

CB49 

20EE 

CB41 

20E1 

18D4 



00100 
00110 
00 1 20 
00130 
00140 
00150 
00160 
00170 
00180 
00190 
00200 
00210 
00220 
00230 
00240 
00250 
00260 
00270 
00280 
00290 
00300 
00310 
00320 
00330 
00340 
00350 
00360 
00370 
00380 
00390 
00400 
00410 
00420 
00430 
00440 
00450 
00460 
00470 
00480 
00490 
00500 
00510 
00520 
00530 
00540 
00550 
00560 
00570 
00580 
00590 
00600 
00610 
00620 



ORG 9000H 
; ******************************************************** 
;* TELEPHONE DIALER. DIALS ANY NUMBER OF DIGITS FOR * 
;* ROTARY-TYPE PHONE THROUGH CASSETTE PORT. * 

;* ENTRY: HL=> STRING OF ASCII DECIMAL DIGITS* TERM- * 
;* INATED BY NON-ASCII * 

;* EXIT: AFTER NUMBER HAS BEEN DIALED * 

; ******************************************************** 



PULSE 
WAIT1 
WAIT2 
TELDIL 



EQU 
EQU 
EQU 
CALL 
PUSH 
POP 
LD 
SUB 
JR 
LD 
JR 
CP 
JR 
LD 
LD 
OUT 
LD 
LD 
JR 
LD 
OUT 
LD 
LD 
JR 

DJNZ 
LD 
LD 
JR 
INC 
JR 
RET 

; DELAYS 24.8 
DELAY DEC 
LD 
LD 
LD 
OR 
JR 
BIT 
JR 
BIT 
JR 
JR 
END 



TEL005 



TEL010 



TEL020 



TEL030 



TEL040 



TEL050 
TEL090 



1540 

2460 

30740 

0A7FH 

HL 

IX 

A, <IX> 

30H 

NZ,TEL010 

A, 10 

CTEL090 

11 

NCTEL090 

B,A 

A,l 

<0FFH),A 

HL, PULSE 

C,0 

DELAY 

A,2 

<0FFH),A 

HL,WAIT1 

CI 

DELAY 

TEL020 

HL,WAIT2 

Ci2 

DELAY 

IX 

TEL005 

1*CNT IN MICROSECS 
HL 
AjR 
A,R 
A,H 
L 

NZ, DELAY 
1, C 

NZiTEL050 
0, C 

NZ,TEL040 
TEL030 



;38.5 MS PULSE 
!10 PULSES PER SECOND 
;830 MS INTERDIGIT 
;GET ARGUMENT IN HL 
;MOVE TO IX 
J IX POINTS TO STRING 
;GET NEXT DIGIT 
; CONVERT TO BINARY 
;GO IF NOT 
5 0-USE 10 PULSES 
;RTN IF LT 30H 
;TEST FOR GT 10 
; RETURN IF GT 10 
;# OF PULSES IN B 
;ON CODE 
?TURN ON RELAY 
; DELAY CONSTANT 
! RETURN FLAG 
; DELAY 
;OFF CODE 
?TURN OFF RELAY 
; BETWEEN PULSE DELAY 
; RETURN FLAG 
; DELAY 

SLOOP IF MORE PULSES 
; BETWEEN DIGITS DELAY 
; RETURN FLAG 
; DELAY 

?BUMP STRING POINTER 
iLOOP FOR NEXT DIGIT 
; RETURN TO BASIC 
+ OVERHEAD 

DECREMENT DELAY COUNT 
;TIME WASTER 
5TIME WASTER 
?TEST HL 

SLOOP IF NOT DONE 
■TEST FOR RTN PNT 2 
SGO IF RTN PNT 2 
i TEST FOR RTN PNT 1 
SGO IF RTN PNT 1 
SRTN PNT 



DELAY is a simple time-delay 
routine that delays 24.81 ^s times the 
HL count. To keep the code relocat- 
able, DELAY is not entered via an or- 
dinary CALL, which would have a 
nonrelocatable address, but is called 
with a code for the three return 
points. 

Listing 5 shows the machine- 
language code of TELDIL incor- 
porated within a BASIC program. In 
this case, it is moved to 9000 hexa- 
decimal, but it could be relocated to 
any convenient area in memory. The 
ASCII string is INPUT and a 
CHR$(0) is concatenated to the string 
for the terminating character. 

VARPTR is used to find the string 
location. Make certain that VARPTR 
is used immediately before the USR 
call because string variables move. 
The "C-65536" adjusts for addresses 
in the upper 32K bytes of RAM; for a 
32K- or 48K-byte system, this would 
normally be the area in which string 
variables would be located. String 
variables within a BASIC program 
line, however, have addresses that 
represent the location of the program 
line, and the argument in the USR call 
must be adjusted accordingly. 

Constructing the TELDIL Circuit 

TELDIL uses the project board 
discussed earlier (see TONOUT). The 
components are connected as shown 
in figure 13. Power-supply voltage 
should be more than 6 V; the relay 
shown will not work well with a 5-V 
supply. The cassette plug is connected 
as shown in figure 8. 



Listing 5: A BASIC program to demonstrate telephone dialing via the TRS-80 cassette 
port. The DATA statements contain the machine-language codes of the TELDIL 
subroutine. 



40 F 


iEM SAMPLE TELDIL DRIVER 




60 A=-0:B^0:C^0:Ain=" " 




E*0 DATA 205, 127, 10, 229, 221, 225, 221 


» 126, 0, 


100 


DATA 48, 32, 2, 62, 10, 56, 40, 254, 


lli 48 


120 


DATA 36, 71, 62, 1, 211, 255, 33, 4, 


6, 14 


140 


DATA 0, 24, 25, 62, 2, 211, 255, 33, 


156, 9 


160 


DATA 14, 1, 24, 14, 16, 232, 33, 20, 


120, 14 


180 


DATA 2, 24, 5, 221, 35, 24, 205, 201 


, 43, 237 


200 


DATA 95, 237, 95, 124, 181, 32, 247, 


203, 73, 


220 


DATA 238, 203, 65, 32, 225, 24,212 




240 


CLEAR 500 




260 


DEFUSRH=&H9000 




280 


FOR 1=36864-65536 TO 36940-65536 




300 


READ A: POKE I, A 




320 


NEXT I 




340 


INPUT A$: A*=A$+CHR*<0> 




360 


B=VARPTR<A$) 




380 


C=PEEK ( B+ 1 ) + < PEEK < B+2 ) ) *256 




400 


A=USR0< C-65536) 




420 


GOTO 340 





A Serial Driver 

Our third project using the cassette 
output is an RS-232C output port that 
can be used to drive a serial printer, 
modem, or other serial device. Stan- 
dard rates of 300, 600, 1200, and 2400 
bps can be selected with 10 bits per 
character. 

RS-232C signals appear as shown 
in figure 14. A voltage level below 
— 3 V represents a 1 bit; a voltage 
level above +3 V represents a bit. 
Although the number of bits in a 
transmission varies, a common con- 
vention used with the TRS-80 is 
shown in figure 14. 



174 April 1982 © BYTE Publications Inc 



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BYTE April 1982 175 






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HELP IS COMING 
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TO CASSETTE PLUG 



+ 6V 



RADIO SHACK 
276-175 
EXPERIMENTER 
SOCKET 




WIRING DIAGRAM 
(SEE FIGURE 6) 



TO 

TELEPHONE 
DATA ACCESS 
ARRANGEMENT 



Figure 13: The TELDIL circuit is mounted on a project board. The relay leads can be 
trimmed, "built-up" with solder, and pushed into the project-board holes. 



+ 3 TO +15V 
(0 LEVEL) 



-3 TO -15 V 
( 1 LEVEL) 



-10 BITS /CHARACTER TYPICAL — 
CHARACTER SHOWN IS ASCII "l" 



-START BIT =0 
1 



'/////////////////////A 

1 



/////////////////^ 



--3V TO +3V 
SIGNALS 
NOT RECOGNIZED 



STOP BIT 



J 



J 



Figure 14: Logic is inverted in standard RS-232C signals. A 1 is represented by a 
negative voltage; aO by a positive voltage. Voltage levels from —3 to +3 V will not be 
recognized as legitimate values. 



178 April 1982 © BYTE Publications Inc 



WESTKO-The Software Express Service that really delivers: 




IISOFTWARE 
IIFOR 
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MILESTONE™ -Critical Path Method 
project management. Displays and 
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Fof 






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Dealer inquiries invited. WES-45 

Copyright © 1982 Westico, Inc. 

WESTICO 

The Software Express Service 

25 Van Zant Street •Norwalk, Connecticut 06855 
(203) 853-6880 • Telex 643-788 



Circle 480 on inquiry card. 



Each byte to be transmitted occurs 
at asynchronous, or irregular, times. 
The line is normally at a 1 level. A 
start bit leads the output and signals 
the receiving device that data are 
coming in. Eight data bits follow, 
with the least significant bit first. A 



stop bit puts the line at the 1 level 
after transmission, in preparation for 
the next character. 

The spacing for the 10 bits depends 
upon the transmission rate. Rates of 
300, 600, 1200, and 2400 bps (bits per 
second) represent "bit times" of 



+ 6V TO +12V +6V TO +12V 

A 



CASS0UT O 




^h 



+> SGND 



^START BIT = 
8 DATA BITS 

Jtxxxxxxxx_: 

STOP BIT = \-^ 



-6V TO -12V 



Figure 15: The SEROUT project uses an operational amplifier to generate a positive and 
negative voltage representing R5-232C data signals. Any convenient positive and 
negative voltage may be used. 



Listing 6: SEROUT is a Z80 subroutine to perform R5-232C output through the Model 
l/lll cassette port. 



9000 




00100 




ORG 


9000H 










00110 


;*******************#*********************************** 






00120 


;* SERIAL OUT 


THROUGH CASSETTE 


PORT. 






00130 


;* ENTRY: 


H=BYTE TO BE 


TRANSMITTED 






00140 


;* 




L=BAUD RATE: 


300= 


=20 1 , 600= 1 00 i 1 200=5 1 > 






00150 


; * 






2400=23 (MOD I)/ 230*115, 






00160 


; * 






58,: 


."6 (MOD III) 






00170 


;* EXIT: 


AFTER OUTPUT 










00180 


;******************************************************* 






00190 


; 










9000 


CD7F0A 


00200 


SEROUT 


CALL 


0A7FH 




;GET PARAMETERS 


9003 


54 


00210 




LD 


DiH 




;MOVE DATA TO D 


9004 


2600 


00220 




LD 


Ht0 




?HL NOW HAS DELAY CNT 


9006 


E5 


00230 




PUSH 


HL 




; TRANSFER CNT TO IY 


9007 


FDE1 


00240 




POP 


IY 






9009 


3E02 


00250 




LD 


A, 2 




5START BIT 


900B 


D3FF 


00260 




OUT 


(0FFH)j A 




; OUTPUT 


900D 


FDE5 


00270 




PUSH 


IY 




; DELAY CNT TO HL 


900F 


El 


00280 




POP 


HL 






9010 


0E00 


00290 




LD 


C>0 




;FLAG FOR RTN 


9012 


1820 


00300 




JR 


DELAY 




; DELAY ONE BIT TIME 


9014 


0608 


00310 


SER040 


LD 


Bi8 




; SETUP DATA BIT LOOP 


9016 


3E02 


00320 


SER050 


LD 


A, 2 




?0 BIT TO A 


9018 


CB3A 


00330 




SRL 


D 




; SHI FT OUT DATA BIT 


901A 


3001 


00340 




JR 


NCiSER055 




;GO IF DATA BIT=0 


90 1C 


3D 


00350 




DEC 


A 




5DATA BIT=1 


901D 


D3FF 


00360 


SER055 


OUT 


(0FFH),A 




; OUTPUT 


901F 


FDE5 


00370 




PUSH 


IY 




; DELAY CNT TO HL 


9021 


El 


00380 




POP 


HL 






9022 


0E01 


00390 




LD 


C, 1 




5FLAG FOR RTN 


9024 


180E 


00400 




JR 


DELAY 




; DELAY 


9026 


10EE 


00410 


SER060 


DJNZ 


SER050 




5 LOOP IF MORE BITS 


9028 


3E01 


00420 




LD 


A, 1 




5STOP BIT 


902A 


D3FF 


00430 




OUT 


(0FFH), A 




; OUTPUT 


902C 


FDE5 


00440 




PUSH 


IY 




; DELAY CNT TO HL 


902E 


El 


00450 




POP 


HL 






902F 


0E02 


00460 




LD 


Ci2 




;FLAG FOR RTN 


9031 


1801 


00470 




JR 


DELAY 




; DELAY 


9033 


C9 


00480 


SER070 


RET 






; RETURN TO BASIC 






00490 


? DELAYS 14.6 


*CNT IN MICROSECS 


(MOD I) + OVERHEAD 


9034 


2B 


00500 


DELAY 


DEC 


HL 




DECREMENT DELAY COUNT 


9035 


7C 


00510 




LD 


A,H 




;TEST HL 


9036 


B5 


00520 




OR 


L 






9037 


20FB 


00530 




JR 


NZ, DELAY 




SLOOP IF NOT DONE 


9039 


CB49 


00540 




BIT 


1»C 




?TEST FOR RTN PNT 2 


903B 


20F6 


00550 




JR 


NZ,SER070 




;GO IF RTN PNT 2 


903D 


CB41 


00560 




BIT 


05 C 




5TEST FOR RTN PNT 1 


903F 


20E5 


00570 




JR 


NZ>SER060 




;GO IF RTN PNT 1 


9041 


18D1 


00580 




JR 


SER040 




;RTN PNT 


0000 




005<?0 




END 









3.333, 1.666, 0.833, and 0.416 ms, 
respectively. 

The chief problem now is to con- 
vert the low voltage levels of 
CASSOUT into the two RS-232C 
voltages. This is done with an LM741 
comparator, as shown in figure 15. 
The supply voltages used with the 
comparator are + 6 to + 12 V and —6 
to —12 V. Batteries will work fine, 
and the voltages are not critical. 

The voltage-divider input to the 
plus (" + ") input of the LM741 is 
biased at about (220/15000) X V + , 
where V+ is the positive supply 
voltage. This puts the plus input at 
about 1/10 V for a +6-V supply, or 
about 1/20 V for a +12-V. The out- 
put of the 741 will be -6 to -12 (1 
level) whenever CASSOUT is greater 
than the plus input level, and +6 to 
+ 12 V (0 level) whenever CASSOUT 
is less than the plus input level. 

BASIC initializes the port control- 
ling CASSOUT to binary 00 (0.44 V), 
and so the TD (transmit data) line at 
reset is normally —6 to —12 V. By 
toggling the CASSOUT line at the ap- 
propriate rate, you can generate the 
RS-232C signals. 

SEROUT (see listing 6) is a 
relocatable assembly-language pro- 
gram called from BASIC by a USR 
call. Two parameters are passed: the 
byte to be transmitted and the 
transmission rate to be used. The byte 
can be any value from through 255. 
If seven data bits are to be transmit- 
ted (as in data-communications ap- 
plications), make the eighth bit 0. 

SEROUT first picks up the trans- 
mission-rate code and puts it into the 
HL register pair. The code is a delay 
count for the DELAY subroutine. The 
byte to be transmitted is moved to the 
D register. 

Line 260 turns on CASSOUT to 
generate a start bit. A delay of one bit 
time is then done. The loop from lines 
320 through 410 outputs the eight 
data bits, from least significant to 
most significant. A 1 bit is generated 
by sending a 01 to port OFF hexa- 
decimal, and a bit is generated by 
sending a 10. A duration of one bit 
time is used for each bit. 

A stop bit is generated in line 430 
after the eight data bits. This leaves 
the TD line at the 1 level in prepara- 



180 April 1982 © BYTE Publications Inc 



tion for the next start bit. 

The DELAY subroutine is called by 
relative jumps with a return flag to 
keep the code relocatable. 

Listing 7 shows a sample BASIC 
driver that contains the machine code 
for SEROUT as DATA statements. 



The code is relocated to start at 9000 
hexadecimal. For demonstration, an 
ASCII is continually output at a 
user-specified rate. 

The actual BASIC code to be used 
depends a great deal upon the ap- 
plication. If you are using SEROUT 



Listing 7: A sample BASIC driver for the SEROUT subroutine. The DATA statements 
contain machine-language codes for the subroutine. This program outputs a continuous 
stream of ASCII zeros. 



J 0O REM SAMPLE SEROUT DRIVER 
110 DATA 205. 127, l.tf< 8'm 3S< 
J 20 DATA 2» 21 J, 253 » 253i 229, 
130 DATA 6, 8? 62* 2, 203, 5'cU 
140 DATA 255 i 253, 229, 225, i 4 
i50 DATA 62i 1, 21:1. , 2'3'i, 253? 
160 DATA 1, 20 J, 43, 124, 181 , 
170 DATA 246, 203, 65, 32, 229, 
1B0 FOR 1=36864 TO 36930 

190 READ A: POKE I 6^536, A 

200 NEXT I 

210 DEFUSR0=&H9tfl00 

220 INPUT "RATE 2" ' RT 

230 CH=4S 

240 B=USR0(CH*256+RT) 

250 GOTO 2'+0 






4i9, 

? 1. , 

229, 



, 14, 
1 , 61, 211 
2'i , 14, 16- 



25 1 j 
i 209 



;;:03» 73, 




-6V TO 
-12V 



® 



Figure 16: The SEROUT circuit is mounted on a project board. Two sets of power- 
supply connections are required. 




SQV MicroGANTT is a 

^^ sophisticated project 
planning system which 
uses Critical Path Method 
(CPM) techniques and PERT to 
determine task dependencies 
and project completion dates. 
The user creates tasks, assigns 
costs and defines task depend- 
encies. The interactive system 
immediately redisplays the proj- 
ect plan as data is entered, 
Projects are displayed as Gantt 
charts, labor time summaries and 
financial summaries. 

MicroGANTT features: ■ Time 
scale of days, weeks, months, 
quarters or years can be varied at 
any time to present more or less 
detail. Accommodates unlim- 
ited number of tasks in a project 
plan. Detailed sub-projects can 
be included as tasks in a project 
model. Assumptions are easily 
modified to make "What if?" 
analyses. Single key-stroke com- 
mands page through tasks and 
calendar of events on display 
screen. Single key-strokes switch 
the display from Gantt chart to 
labor time summary to financial 
summary. Partial allocation of 
manpower to tasks. Partial 
completion of prerequisite tasks. 
All charts, reports and plans can 
be printed. 

Available for IBM Personal 
Computer and CP/M compatible 
computers, Software and manual 
$395. Manual alone $25. 

4 ways to order: 

• Write Westico. Inc., 25 Van Zant Street. 
Norwalk. CT 06855 

• Call (203) 853-6880 

• Telex 643-788 

• Dial-up our 24-hour computer 
(300 baud) (203) 853-0816 



copyright © 1982 Westico, Inc. 



WES-44 



WESTICO 

The Software Express Service 



April 1982 © BYTE Publications Inc 181 











NEC 
CABLE 






TD 


TOGETHER t-_ 




4 
5 
3 
6 
8 
20 
7 




v^ 




FROM 
SEROUT 


\ 


RD 


GND 


\ 




CIRCUIT 


\ 










SGND 











Figure 17: / connected an NEC Spinwriter to the SEROUT circuit with two wires and 
some "jumper" interconnections on the Spinwriter side. Other RS-232C devices will re- 
quire similar connections. 



as a printer driver, you'll have to 
make certain that the printer can ac- 
cept characters at the rate you'll be 
transmitting. This is usually not a 
problem except on carriage 
return/line feeds where the print 
mechanism is busy for relatively long 
times as the carriage returns. If a 
character is output during this busy 
condition, it may be disregarded and 
lost. 

The bit-delay times shown are 



values obtained by trial and error 
with the real-time clock active. You 
may have to adjust these on an ex- 
perimental basis, depending upon 
your system. Output a line of 
characters continuously at different 
bit rates. Find the high and low values 
at which you start to lose characters 
and choose a midpoint value for your 
standard bit rate. For high bit rates, 
turn off the interrupts using DI and EI 
as described in TONOUT. 



Constructing the Electronics 

Figure 16 shows the project-board 
layout for SEROUT. Two sets of 
power-supply leads connect to the 
positive and negative supplies. The 
TD line and ground connect to the 
serial device. 

The serial device may require other 
signals to be tied high to simulate a 
"ready" condition. Again, this 
depends upon the device and can't be 
detailed here. A typical connection to 
an NEC Spinwriter is shown in figure 
17. 

The projects presented here show 
what can be done with the cassette 
output port on a lowly 16K-byte 
TRS-80 Model I without an expan- 
sion interface. I'll cover transmission 
in the opposite direction— CASSIN— 
in another article. Perhaps by then 
the breeder reactor program will be 
working for CASSOUT. Hmmm . . . 
I keep getting these "Coolant 
Temperature Critical" indica- 
tions. . . . ■ 




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da Hwc 



182 April 1982 © BYTE Publications Inc 



Circle 137 on inquiry card. 



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Name. 



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Green phosphor screen 
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Combination monochrome adapter 
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Simultaneous graphics 
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RS232C interface 

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Because we put what 
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It's all here. And you're looking at it. 

From the 8088 microprocessor and the Macro 
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All told, no other personal computer offers as 
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Software? IBM Personal Computer DOS. The 
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device driver routines. For high level languages, 
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If you're interested, 
start by writing to: 
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The IBM Personal Computer 

Circle 200 on inquiry card. 



The Input /Output Primer 

Part 3: The Parallel and 
HPIB (IEEE-488) Interfaces 



An introduction to two common interfaces 
between computers and other devices. 



Steve Leibson 

Auto-Trol Technology Corporation 

12500 North Washington St. 

POB 33815 

Denver, CO 80233 



This article is the third in Steve 
Leibson s six-part series, The Input/ 
Output Primer. The series describes 
problems involved in communications 
between computers and the outside 
world and explains how some of these 
problems have been solved. The three 
remaining articles will discuss BCD 
and serial interfaces; character codes; 
and interrupts, buffers, grounds, and 
signal degradation. "An I/O 
Glossary, " which defines many terms 
used in these articles, appeared with 
the series' first installment (February 
1982 BYTE, page 122). 



Last month, in addition to describ- 
ing interrupts and DMA (direct 
memory access), I presented general 
information about interfaces. In this 
article, I'll examine two specific types 
of hardware interfaces: the parallel 
and the HPIB or GPIB (IEEE-488) in- 
terfaces (see Robert Katz's review of 
the Hewlett-Packard Interface Loop, 
page 76). 

First, however, let's briefly review 
why these interfaces are necessary. 



As information-processing machines, 
computers require paths for raw data 
to enter and for processed informa- 
tion to exit. A common computer- 
design technique is to create one 
universal path leading both into and 
out of the processor. That path is the 

Data Inversion occurs 

In software, not In the 

Interface. 

I/O (input/output) bus. 

This concept simplifies computer 
design but introduces a complication: 
whatever the design of the I/O bus, 
the computer will be incompatible 
with many I/O devices. Some older 
devices use different signal levels; 
other devices have different data for- 
mats. Most devices will be slow 
enough to degrade the computer's 
performance seriously if it must wait 
on every data transaction. 

The complication is solved through 
the use of interfaces, which act as 
transformers of voltage levels, data 
formats, and transaction speeds. In- 



terfaces enable the computer to com- 
municate with a vast array of 
peripheral devices. 

The Parallel Interface 

Simple peripherals often have in- 
terface requirements much like those 
of the computer's I/O bus. Data is 
transferred over a set of data lines 
(usually 8); a signal line indicates 
when the next chunk of information 
is ready. On a second signal line, the 
peripheral indicates its readiness to 
accept another piece of data. 

This type of interface is a parallel 
interface, so named because the data 
lines are parallel, and multiple bits of 
data are simultaneously transferred in 
parallel. The HP 98032A is a parallel 
interface designed for Hewlett- 
Packard's 9800-series computers. The 
I/O bus described in earlier in- 
stallments of this primer was taken 
from the 9800 computer. I'll use the 
98032A 16-bit interface as an example 
of parallel interfacing. 

Keep in mind that the I/O bus has 
16 bidirectional data lines. Data is 
handled in 16-bit chunks and flows 



186 April 1982 © BYTE Publications Inc 



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REGISTER 



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V LIN 



OUTPUT 
ES 



fc 







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INPUT 
REGISTER 



c 



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J> LINES 



STROBE 
I/O 



FLAG «#- 
STATUS *«- 



CONTROL 
CIRCUITRY 



7*> 



DATA LINES 



~^s 



^ PERIPHERAL ADDRESS LINES 



Figure 6: Block diagram of the Hewlett-Packard 98032 parallel interface. The parallel 
interface consists of registers and buffers. One register is for output, the other for input. 
The 32 unidirectional lines can be used as one set of bidirectional lines. If a peripheral 
has a bidirectional interface, these two sets of lines can be connected to form a bidirec- 
tional peripheral bus. Control circuitry in the interface accepts information from the 
computer and then sends the information to the peripheral. The same control circuitry 
can also, at the request of the computer, request information from the peripheral, then 
signal the computer when the information has been acquired. 



over these lines either into or out of 
the computer, but not in both direc- 
tions at the same time. 

The 98032A interface splits the I/O 
bus into two sets of data lines: 16 out- 
put lines and 16 input lines (see figure 
6). This configuration is more com- 
patible with unidirectional periph- 
erals. Excess lines are left uncon- 
nected. Out of 32 data lines, only 8 
might be used by a unidirectional, 
8-bit peripheral. 

As mentioned above, interfaces 
sometimes serve to transform the sig- 
nal voltage levels used on an I/O bus 
to those required by a peripheral. 
Our sample I/O bus uses TTL (tran- 
sistor-transistor logic) levels, mean- 
ing that a low logic level is repre- 
sented by a voltage between and 
+ 0.7 volts (V). A high logic level is 
represented by a voltage between 
+ 2.0 and + 5.5 V. The input lines of 
the 98032A parallel interface connect 
to TTL circuitry in the interface, so 
TTL levels are required from the 



peripheral. The data output lines of 
the 98032A are driven by transistor 
circuits that can withstand +30 V for 
a high level. The low level is still be- 
tween and +0.7 V for TTL com- 
patibility. 

Remember that when discussing 
logic signal lines, only two signal 
levels are allowed. One level cor- 
responds to a logic 1 and the other to 
a logic 0. If the higher voltage cor- 
responds to a logic 1 and the lower 
level to a logic 0, the signals are said 
to be positive-true. If the lower 
voltage level corresponds to a logic 1 
and the higher voltage to logic 0, the 
signal is called negative-true. 

To sum up: 

1. I/O bus lines are the conductors 
used to transfer data between the 
computer and the interface. 

2. Interface input and output lines are 
the conductors used to transfer 
data between the interface and the 
peripheral. 



188 April 1982 © BYTE Publications Inc 



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LIFEBOAT HAS THE ANSWER 



t 



3 



(la) 




Input Registers 




Register Code 






Function 


R4 
R5 
R6 
R7 






Data Input 
Interface Status 
High Byte Data Input 
(Not Used) 


(lb) 




Output Registers 




Register Code 






Function 


R4 
R5 
R6 
R7 






Data Output 
Interface Control 
High Byte Data Output 
Data Transfer Trigger 


Table 1: Interface definitions for the 98032 A parallel inter j 
input registers, and table lb defines the output registers. 


ace. Table la defines the 



Register Architecture 

I stated earlier that each interface 
would have a unique address on the 
I/O bus and would be selected by the 



peripheral address line on that bus. 
Each interface is divided into registers 
that are individually addressable by 
means of a register code. The register 



model divides the interface into eight 
different registers. Four of these are 
output registers that take data from 
the computer (the computer outputs 
to them). The other four are input 
registers, supplying data to the com- 
puter (the computer gets input from 
them). 

Let's now assign a function to each 
of these interface registers. The 
98032A interface uses the definitions 
shown in tables la and lb. 

R4 registers are the primary means 
of data transfer between the com- 
puter and the interface, and in turn, 
the peripheral. The R4 output data 
register is directly connected to the 
output signal lines of the 98032 A. The 
R4 data input register is connected to 
the interface input lines. The R6 input 
and R6 output registers allow the 
98032A to be used as two 8-bit inter- 
faces instead of one 16-bit interface. 
The R6 registers read or control the 
upper eight data lines when the inter- 
face is in the byte mode, that is, when 
the interface is handling data in 8-bit 



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R5 Input Register (Interface Status) 



Bit #: 7 6 5 4 3 2 1 

Bit Name: INT DMA 1 IID IOD STIl STIO 

Table 2a: R5 input register. This register contains interface 
and peripheral status information. 



R5 Output Register (Interface Control) 



Bit #: 7 6 5 4 3 2 1 

Bit Name: INT DMA RESET AHS X X CTLl CTLO 

Table 2b: R5 output register. This register is used to con- 
trol the interface and peripheral devices. 



units instead of 16-bit units. 

When the computer places data in 
the R4 output register, the pattern of 
that data appears on the output signal 
lines. However, when the computer 
reads the R4 input register, the data 
reflects only the contents of the R4 in- 
put register; it may not reflect the cur- 
rent state of the interface input lines. 
(To clarify this difference, I'll look 
closely at how the interface com- 
municates with a peripheral. First, 
however, I'll finish discussing the re- 
maining registers.) 

Control and Status Registers 

The computer uses the R5 input 



and R5 output registers to control the 
interface and to read the interface and 
peripheral status. The R5 input 
register contains several pieces of im- 
portant status information. Only the 
lower 8 bits of this register are used. 
The meanings of these 8 bits are listed 
in table 2a. 

The INT and DMA bits are used 
for interrupts and direct memory ac- 
cess, both of which were discussed 
last month. Bits 5 and 4 are interface 
identification bits. The 10 pattern (bit 
5 set to 1, bit 4 set to 0) identifies the 
98032A interface as a type 2 interface 
(10 is 2 in binary). Software in the 
computer uses the interface ID bits 



(bits 3 and 2) to decide how to com- 
municate with the interface. The 
proper software driver must be 
selected to operate the interface. 
Other types of interfaces have dif- 
ferent ID patterns and call for dif- 
ferent drivers. 

Computer software can also use the 
IID and IOD bits. IID stands for in- 
vert input data; IOD stands for invert 
output data. These bits allow the 
computer to interface with peripher- 
als using either positive-true or 
negative-true signals. The IID and 
IOD bits are set with jumper wires in 
the 98032A interface. 

It's important to note that data in- 



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HOW TO ORDER Phone orders using American Express, Visa, MasterCharge. Bank wire transfer, Cashier's or Certified check, Money Order, or Personal check (allow 10 
days to clear). Please add 5% for shipping, handling and insurance minimum $500.00. Conn, residents add 7.5% sales tax. All equipment is subject to price changes and 
availability without notice. All equipment is new and comes complete with manufacturers warranty. Showroom prices may differ from mail-order advertisement 



CP/M is a trademark of Digital Research Coip 
' 1 lo 4 piece domestic U S price 



(203) 288-2524 • Telex: 956014 




Colonial Data Services Corp. 

105 Sanford Street Hamden, Conn. 06514 



192 April 1982 © BYTE Publications Inc 



Circle 89 on inquiry card. 



Circle 37 on inquiry card. 



ALPHANUMERIC or GRAPHIC? 

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BMC USA, INC. 



LOS ANGELES 

20610 Manhattan Place Suite 112, Torrance, CA. 90501 
Telex: 698641 BMC USATRNC Phone: 213-320-9880, 9881 



NEW YORK OFFICE 

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Telex: 133221 BMC NY CARL Phone: 201-939-7079, 7061 



INTERFACE 

ACKNOWLEDGES 

REQUEST 



I/O BUS 
FLG LINE 



PCTL 



CONTROL CLEAR 

CONTROL SET 
BUSY 
PFLG 

READY 




COMPUTER 


PERIPHERAL 


REQUEST 


REQUESTS 


ACKNOWLEDGES 


FULFILLED 


TRANSLATION 


REQUEST 





Figure 7: Representation of the handshake between the HP 98032 parallel interface and a 
peripheral device. When the computer requests a transaction, the interface uses the FLG 
line on the I/O bus to signal the computer that it's busy. Then, the PCTL (peripheral 
control) line is set to request an operation by the peripheral. Later, the peripheral 
acknowledges the request by setting the PFLG (peripheral flag) line to busy. When the 
peripheral completes the transaction, it sets the PFLG line to ready, causing the interface 
to lower the I/O bus flag line and thereby tell the computer that the transaction is com- 
plete. This sequence governs both input and output. Direction lines between the com- 
puter, the interface, and the peripheral determine the direction of the transaction. 



version occurs in software, not in the 
interface. The computer may choose 
to ignore these status bits for certain 
classes of I/O operations. Other in- 
terfaces may implement data inver- 
sion in hardware so that, if selected, 
the inversion will always occur. 

The two remaining bits in the inter- 
face status register, STIl and STIO, 
are status inputs brought out on two 
signal lines. The peripheral can call 
on these for any user-defined func- 
tion. Unlike the R4 input register, the 
STIl and STIO bits reflect the current 
state of the STI signal lines. 

Interface control is through the R5 
output register. Table 2b lists the bit 
pattern for this register. The INT and 
DMA bits are used in the interrupt 
and direct memory access modes 
mentioned earlier. The RESET bit is 
used to place the interface in the in- 
itial power-up state. It can also be 
used to reset the attached peripheral 
to a known state if the peripheral has 
a reset input. I/O processes often 
stall, for example, when the printer 
runs out of paper or a disk drive door 
is left open. A reset capability allows 
the computer to change its mind and 
stop what it has started. 

The AHS bit enables auto-hand- 



shake. When this bit is set, the data- 
transfer trigger (R7 output) isn't 
needed. This characteristic is conve- 
nient for high-speed transactions and 
is habitually used with DMA. Bits 3 
and 2 are unused in the R5 output 
register. 

CTLl and CTLO are general-pur- 
pose control bits. These register bits 
are connected to two signal output 
lines and can be used to control the 
attached peripheral device. A signal 
over these output lines can be given 
to latch a printer door shut while 
printing is taking place. 

Peripheral Handshaking 

Note that the R7 output register is 
called the data-transfer trigger. When 
used in conjunction with the R4 input 
and output registers, the data-transfer 
trigger forms a handshake mechanism 
that synchronizes the fast computer 
and the slower peripheral. 

Placing data on the output lines or 
reading the levels on the input lines 
connecting the interface to a 
peripheral device isn't sufficient for 
smooth data flow. A set of signals in- 
dicating "new data available" and 
"ready to accept data" is needed. 

These signal lines are called hand- 



shake lines. The interface and the 
peripheral each control a handshake 
line. The meaning of the signal for 
each line depends on the direction of 
data flow. If the computer is sending 
through the interface to the peripher- 
al, the line controlled by the com- 
puter means "new data available." 
The line controlled by the peripheral 
would then signify "ready for new 
data." If the data flow is reversed, the 
signal meanings are also reversed. 

Let's call the line controlled by the 
interface the peripheral control 
(PCTL) and the line controlled by the 
peripheral the peripheral flag (PFLG). 
With the addition of these two lines, 
the foundation is laid for discussing 
the handshake mechanism. 

Data Output 

Output is simpler than input. As 
has been mentioned, the computer 
can set the state of the interface out- 
put lines by placing information in 
the R4 output register. The hand- 
shake is started when the computer 
performs a write to the interface's R7 
output register. 

The interface recognizes the data- 
transfer trigger and responds by 
changing the state of PCTL from 
"clear" to "set," which indicates to the 
peripheral that "new data is ready" 
on the interface's output lines. The 
peripheral is expected to acquire the 
data now. The peripheral responds to 
"new data ready" by changing PFLG 
from the "ready" to "busy" state. This 
means the peripheral is busy accept- 
ing the data. 

From the time the computer per- 
forms the R7 output register write un- 
til the time the peripheral returns to a 
"ready" state after processing the 
data, the interface is busy carrying 
out the transfer. It's extremely impor- 
tant that the computer not change the 
R4 output register during this time. 
Otherwise, there's no way to tell 
what data the peripheral will get. For 
this reason, the interface and the 
computer also have a handshake 
mechanism. While the interface is 
busy sending the information to the 
peripheral, the interface indicates this 
situation to the computer on the in- 
terface flag line. Figure 7 illustrates 
the peripheral-interface handshake. 



194 April 1982 © BYTE Publications Inc 



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Data Input 

Data input from a peripheral is 
more complex. Three steps are in- 
volved. First, the computer reads the 
R4 input register to let the interface 
know that a data-input operation is 
pending. (The computer throws away 
the data obtained.) The interface 
recognizes this and indicates the 
situation to the peripheral with a 
data-direction line (this line tells the 
peripheral which direction the data is 
to go). 

Next, the computer writes to R7 
output, giving the data-transfer trig- 
ger. This causes the interface to go 
busy and to place the PCTL signal 
line in the "set" state, signifying to the 
peripheral that data is requested. 
The peripheral then goes busy until it 
has acquired the data. It signals its 
busy state on the PFLG line. 

After the peripheral performs the 
operations necessary to get the re- 
quested data, it places the data on the 
interface input lines and returns PFLG 
to the ready state. When the periph- 
eral returns to the ready state, the 
transition of the PFLG signal from 
"busy" to "ready" causes the data on 
the input lines to be placed or 
"latched" into the R4 input register. 
This causes the interface to signal the 
computer that the interface is now 
ready with the requested data. The 
computer then performs another read 
from the R4 input register to get the 
data. 

Note that the R4 input register con- 
tains the information present on the 
input lines at the busy-to-ready tran- • 
sition of the PFLG line. Any changes 
on the input lines after that transition 
will not be reflected in the R4 input 
register. Notice also that the 
peripheral-interface handshake for in- 
put is the same as that for output. 

Some peripherals, by the way, are 
so simple that they can't perform a 
handshake. An example of this would 
occur if the 98032A were used to 
drive signal lights directly. Lights 
have no handshake lines. They 
always follow their data (power) in- 
puts. In these instances, you can con- 
nect the PFLG and PCTL lines to each 
other so that the 98032A handshakes 
with itself. This results in 16 "latched" 
output lines and 16 input lines that 



196 April 1982 © BYTE Publications Inc 



Circle 341 on Inquiry card. 



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BYTE April 1982 197 



may be read on demand. 

Most peripherals using the parallel 
interface use only 8 bits. This allows 
256 combinations (2 8 ) on the data 
lines. If these combinations are 
treated as codes representing charac- 
ters, then 8 bits can represent 
numerals, upper and lower case let- 
ters, punctuation marks, and other 
printable characters. Most periph- 
erals communicate this way, but 
there are exceptions. A floppy-disk 
drive may require the full 16-bit inter- 
face. Some plotters use 12 bits. 
Analog-to-digital converters come in 



10-, 12- or 16-bit sizes. A single 16-bit 
interface can serve all these kinds of 
peripherals. 

The IEEE-488 Standard Interface 

Computer designers strive to incor- 
porate the latest parts and the fastest 
logic in new and different configura- 
tions. In addition, designers of com- 
puter peripherals are always creating 
new classes of devices. The result has 
been a multitude of interfaces, each 
optimized for a single kind of com- 
puter or peripheral. Few of these in- 



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212 448-6283 212 448-2913 212 448-6298 



terfaces are compatible with any of 
the others. 

This situation is similar to that of 
the American railroads during the 
early 1800s. Because dozens of track 
gauges existed, cars of one railroad 
couldn't travel on the tracks of 
another. Reminiscent of the speed 
with which railroads standardized 
track gauges, the computer industry 
quickly agreed on an interfacing stan- 
dard, published in 1975 by the In- 
stitute of Electrical and Electronics 
Engineers (IEEE). It was the first com- 
prehensive, nearly universal interfac- 
ing standard for computers and in- 
strumentation. The first version, IEEE 
Standard Digital Interface for Pro- 
grammable Instrumentation (IEEE- 
STD-488-1975) was slightly revised in 
1978 and is now IEEE-STD-488-1978. 

This standard defines a general- 
purpose interface, one designed for 
instrumentation systems requiring 
limited-distance communications. 
The intent of IEEE-STD-488-1978 
(hereafter, "IEEE-488") is to pin down 
as many variables of an interface as 
possible while still maintaining good 
flexibility and wide applicability. The 
interface is also defined without 
reference to the hardware circuitry re- 
quired to implement the interface. 
This allows new products to take ad- 
vantage of new technologies, result- 
ing in faster and less expensive con- 
struction of instruments, peripherals, 
and systems. 

The HP 98032A parallel interface 
has two separate groups of data lines: 
16 for input and 16 for output. This 
allows interfacing to a wide variety of 
peripherals with varied interfaces. 
Devices with 8, 10, 12, or 16 data 
lines can be accommodated. A 
popular version of the 98032A has a 
cable with no connector attached. 
The system builder must select a con- 
nector and assign the pin numbering 
since there are no standards as to how 
to connect this type of interface. 

By contrast, the IEEE-488 standard 
precisely specifies signal levels (both 
voltage and current) and signal tim- 
ings. Building a system can be as 
simple as removing components from 
their boxes and plugging them in. 
Interconnection hardware is defined 
so that two interconnected instru- 



198 April 1982 © BYTE Publications Inc 



ments can communicate. Their 
understanding each other, however, 
is not guaranteed by the standard. 

Using the IEEE-488 standard is like 
using the international telephone 
system. You can call anywhere on 
earth because a compatible com- 
munications network, the telephone 
system, exists. Sounds you make can 
reach the other end of the connection, 
and you can hear the sounds made by 
the person at that other end. The 
hardware for communications is all in 
place, but there's no guarantee that 
you'll understand what the other per- 
son is saying or vice versa. Hardware 
compatability does not guarantee 
language compatibility. 

Hewlett-Packard has an implemen- 
tation of the IEEE-488 standard which 
it calls the HPIB or Hewlett-Packard 
Instrumentation Bus. HPIB is a com- 
bination of the hardware interface 
specified by the IEEE-488 standard 
and a communications technique that 
makes it possible for instruments to 
communicate with each other. The 
standardization also allows the 
system designer to communicate 
what's going on in the system. 

The IEEE-488 standard is so general 
that almost any peripheral or instru- 
ment can be purchased in an HPIB 
version. Voltmeters, power supplies, 
signal generators, printers, plotters, 
and disk drives are only a few of the 
devices available. All may be con- 
nected on the same bus. 

Unlike the parallel interface, which 
connects a single device with the com- 
puter, the HPIB interface makes it 
possible to connect as many as 15 
devices (including the computer). 
HPIB is indeed a bus, similar in con- 
cept to the I/O bus of the computer. 

Controllers, Talkers, Listeners 

Only two entities reside on the I/O 
bus: the computer and the interface. 
The computer is always in control of 
the I/O bus, and the interfaces are 
slaves, doing the computer's bidding. 

Three types of devices exist on the 
HPIB: controllers, talkers, and 
listeners. These types are actually at- 
tributes and may exist alone or in 
combination within any given 
peripheral. For example, the HPIB in- 



terface allows a computer to be a 
talker, listener, and controller. A 
voltmeter may only be a talker 
limited to supplying the system with 
information, while a printer may 
only be a listener limited to accepting 
data from the system. Further, any of 
the HPIB attributes may or may not 
be active at a given time. 

Figure 8 illustrates how an HPIB 
system might be structured. The lines 
on the right of the figure represent the 
HPIB's 16 signal lines. The 16 signal 



lines are divided into 3 groups, the 
first of which is composed of 8 data 
lines. Forming the data bus, these 
bidirectional signal lines carry infor- 
mation and messages between devices 
on the bus. The second group, the 
data byte transfer control group, is 
composed of 3 lines: DAV (data 
valid), NRFD (not ready for data), 
and NDAC (not data accepted). As 
the names imply, this group is used to 
sequence the flow of information 
over the data lines. The 5 remaining 



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April 1982 © BYTE Publications Inc 199 



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GENERAL 


DATA BYTE 




INTERFACE 


TRANSFER 


DATA 


MANAGEMENT 


CONTROL 


BUS 



V 



^ 



DEVICE A 
ABLE TO TALK, 
LISTEN, AND 
CONTROL 
(e.g., 
COMPUTER) 



n 



^ 



V 



DEVICE B 
ABLE TO TALK 
AND LISTEN 
(e.g., 
MULTIMETER) 



C 



c 



z^ 



V 



DEVICE C 
ONLY ABLE TO 
LISTEN 
(e.g., SIGNAL 
GENERATOR) 



t 



^v 



t 



DEVICE D 

ONLY ABLE TO 

TALK 

(e.g., COUNTER) 



IFC 


DAV 


DIO 


ATN 


NRFD 


(1-8) 


SRQ 


NDAC 




REN 






EOI 







Figure 8: Sample configuration of the IEEE-488-1978 interface bus. Devices on the bus 
can be talkers, listeners, or controllers. Controllers manage the bus, activating and 
deactivating listeners. Talkers place data on the bus. Listeners accept data from the bus. 
A device connected to the bus can be a talker, a listener, a controller, or any combina- 
tion of the three. Most computers, like device A, are talker, listener, and controller so 
that the computer can configure the bus, then send and receive information. Device B, a 
multimeter, can talk and listen, sending readings and receiving set-up information such 
as range and function. Device C, a signal generator, listens only. Printers are usually 
listeners. Device D, a frequency counter, talks only, placing readings on the bus. The 
IEEE-488-1978 bus is divided into three sets' of signals. The data bus carries the informa- 
tion being transferred. Data byte transfer control lines sequence the flow of informa- 
tion. The general interface management lines have special functions: IFC (interface 
clear) resets the bus interfaces; A TN (attention) sends bus commands; and SRQ (service 
request) signals bus interrupts. 



lines form the third group of signal 
lines: the general interface manage- 
ment group. These lines carry control 
and status information about the 
devices connected to the bus. 

Assigning Roles 

Figure 8 shows 4 devices attached 
to the HPIB. Device A has the talker, 
listener, and controller attributes. As 
a controller, device A may assign the 



role of active talker to any device on 
the bus capable of undertaking that 
role, including itself. As a talker, 
device A can supply information to 
other devices on the bus. As a 
listener, device A can accept informa- 
tion from the other talkers on the bus. 
A computer is likely to have all three 
attributes. 

Although device A is the only con- 
troller shown in figure 8, more than 



one controller is allowed in an HPIB 
system. To prevent conflicts, 
however, only one controller can be 
active at a time. Control may be 
passed from one controller to another 
by means of a sequence defined in the 
standard. A controller designated the 
system controller becomes the active 
controller when the system is turned 
on. All other controllers must remain 
passive until control is passed to 
them. 

Device B in figure 8 is both a talker 
and a listener. It can be addressed by 
the controller and made an active 
talker or listener. An active talker 
controls the DAV signal line in the 
data byte transfer control group. An 
active listener controls the NRFD and 
NDAC signal lines. 

Device C can only be a listener. 
Device D is limited to being a talker. 
Either of these devices may be made 
active by the controller. A data trans- 
action is controlled by both the active 
talker and the active listener. The 
talker drives the bus with data, while 
the listener accepts the information 
transmitted by the talker. To avoid 
conflict, only one talker can be active 
at a time. However, several listeners 
can be active at once. 

Transferring Information 

The possibility of several active lis- 
teners receiving data simultaneously 
presents a problem because those 
listeners may not accept data at the 
same rate. Data-transfer speed must 
be paced by the slowest active 
listener, or that listener may lose 
data. 

The data transfer rate on the HPIB 
is controlled by an electronic voting 
system called the open collector. This 
voting system requires unanimous 
agreement among active listeners and 
the active talker before the data trans- 
action is completed. Information 
transfer takes place as follows: 

1. All active listeners indicate on the 
NRFD line their state of readiness 
to accept a new piece of informa- 
tion. This signal line is usually con- 
nected to +5 V through a resistor. 
If an active listener is not ready, it 
pulls the NRFD line down to V 
by turning on a transistor con- 



202 April 1982 © BYTE Publications Inc 



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Address- 



City_ 



i State. 



_Zip_ 



DATA LINES 



DAV 



FALSE 



TRUE 
FALSE 



NRFD 



FALSE 



NDAC 



TRUE 



12 3 4 



Figure 9: Diagram of timing on the IEEE-488-1978 bus. Data transfers occur with a 
unique 3-wire handshake. First, the active talker waits for all active listeners to release 
the NRFD (not ready for data) line. When this happens, the signal rises to a positive 
level. The talker then places the data on the data lines, waits 2 microseconds, and drives 
the DAV (data valid) line low, indicating that the data should now be accepted. 
Recognizing the transition in the DAV line, the active listeners drive NRFD low. The 
active listeners have as much time as necessary to release NDAC (not data accepted). 
When all active listeners do release NDAC, its voltage rises to a positive level. This tells 
the talker to release DAV. At the release of DAV, the listeners pull NDAC low again. 
This restores the bus to the original state, where it is ready for another transfer. 



nected to the signal line. The ac- 
tivated transistor acts as a short to 
ground, pulling the voltage on the 
NRFD line to ground potential or 
V. When the listener is ready to 
accept data, it turns off this tran- 
sistor. When all active listeners 
turn off their transistors, the 
resistor connected to +5 V pulls 
the NRFD signal line up to around 
+ 5 V. The active talker observes 
the state of the NRFD line and will 
not start the data transfer until the 
signal line reaches a high voltage 
level. 
, The active talker observes that the 
NRFD line has gone high. It places 
a data byte on the data lines and 
waits 2 microseconds (0.000002 
seconds). It then asserts DAV by 
pulling it low to V. This 
2-microsecond wait, called settling 
time, allows the data to reach valid 
logic levels on the data lines. The 
assertion of DAV is a signal to the 
active listener(s) to read the infor- 
mation on the data bus. The 



listeners acknowledge the assertion 
of DAV by immediately pulling 
back down on NRFD. 

3. Until now, the active listeners have 
held NDAC low. When DAV is 
asserted and all of the active 
listeners accept the data on the 
data lines, they will release 
NDAC. As the slowest active 
listener releases NDAC, the pullup 
resistor will cause the signal line to 
go high. 

4. The active talker observes the 
NDAC line in a high state. It 
acknowledges the listeners' accep- 
tance of the data by releasing 
DAV. The release of DAV signals 
the listeners that the data transfer 
is complete; they again pull NDAC 
low in preparation for the next 
transfer. 

Figure 9 shows a timing diagram of 
the complete handshake. Note that 
control of the data transfer is effected 
by the active talkers and listener(s). 
Once the controller has configured 
the bus, it takes no part in subsequent 



204 April 1982 © BYTE Publications Inc 



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Information Type 


Bit # 

7 6 


5 


4 


3 


2 


1 





Bus command 
Listen Address 
Talk Address 
Secondary Address 


X 

X 
X 
X 




1 
1 



1 

1 


C 

L 
T 
S 


C 

L 
T 
S 


C 

L 
T 
S 


C 

L 
T 
S 


C 

L 
T 
S 


Table 1: Interface definitions for the 
input registers, and table lb defines 


98032A parallel interf 
h he output registers. 


ice. 


Table la defines the 



transactions until reconfiguration is 
desired. 

Configuring It Out 

Now that data transfer on the HPIB 
has been covered, let's consider how 
the bus is configured. One of the 
general interface management lines is 
called ATN (attention). The active 
controller manages this line. ATN 
signifies whether the data transfers on 
the bus are data or control informa- 
tion. The active talker controls data 
transactions, as explained above, but 



the active controller supervises con- 
trol transfers. 

When the controller wishes to con- 
figure the HPIB, it asserts the ATN 
line. This causes any active talker to 
relinquish control of the DAV line. 
Transmission of control information 
occurs in the same manner as transfer 
of data. The difference is that when 
ATN is asserted, the active controller 
takes the place of the active talker, 
and both talkers and listeners accept 
the information. All devices, whether 
active or not, accept information 



transmitted by the controller when 
ATN is asserted. 

The active talker and active 
listeners may be designated during 
the transmission of control informa- 
tion. The data lines carry control in- 
formation after ATN has been 
asserted. Table 3 lists the meanings of 
the control data bits. 

Note that bit 7 is not used. Bits 6 
and 5 serve to classify the control in- 
formation as to command type. A 
control transfer with bits 6 and 5 set 
to is a bus command that directly 
controls devices on the bus. Trigger- 
ing a function and passing control 
from the active listener to a passive 
one are two examples of bus 
commands. 

Transmission of a control byte 
with bit 6 set to and bit 5 to 1 ac- 
tivates a listener. A listener that 
observes its address in the lower 5 bits 
of a listen address control byte 
becomes active. When ATN is 
negated, it will assume control of 
NDAC and NRFD. Listeners that 




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206 April 1982 © BYTE Publications Inc 



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don't observe their listen addresses in 
a control transfer don't change state, 
remaining as they were before the 
controller asserted ATN. 

Deactivating Listeners 

The HPIB provides a way to deac- 
tivate all active listeners. The 5 bits of 
the listen address allow 32 listen ad- 
dresses. These addresses range from 
to 31. Address 31 is the "unlisten" ad- 
dress. Active listeners observing the 
unlisten address in a listen 
command's address field will go inac- 
tive. The definition of talk addresses 
is similar to that for listen ad- 
dresses — with one exception: any ac- 
tive talker that observes a talk com- 
mand to another device will go inac- 
tive. As a result, activating one talker 
guarantees deactivation of any other 
active talkers. This prevents conflicts 
on the bus. Talk-address 31 is the 
"untalk" address. When the con- 
troller issues an untalk command, no 
active talkers are left on the bus. 

Secondary addresses are used to 
address subunits within a device. 
Some HPIB instruments are actually 
clusters of devices, but secondary ad- 
dressing allows addressing of a device 
within such a cluster. 

The remaining four lines in the 
general interface-management group 
serve to control the interface sections 
of the HPIB devices. IFC (interface 
clear) may be called on by the active 
controller to override all bus activity 
and to place the bus in a known state. 
This signal aborts any data transfers 
in progress and is used only when 
something has gone wrong. 

The REN (remote enable) signal 
allows the HPIB to control a device. 
The active controller uses the REN 
line to indicate to an active listener 
whether or not the listener will use 
the information sent to it by a talker. 

EOI (end or identify) is applied in 
two ways. First, the active talker may 
assert it to designate a data byte as 
the last in a message. EOI is also part 
of a serial poll, which will be dis- 
cussed later. 

The SRQ (service request) signal 
enables a device to get the active con- 
troller's attention. This signal is a re- 
quest, not a demand. The controller 
may ignore SRQ as long as it wishes. 



When the controller finally does 
acknowledge SRQ, it has to deter- 
mine which device is requesting ser- 
vice. Since SRQ is shared by all 
devices on the bus, the requester isn't 
identified immediately. 

Polling Along 

A controller can employ two 
methods to determine the address of 
the device requesting service. Both 
methods are called polls. A poll is the 
controller's request for status infor- 
mation. The controller may request 
the status of any device individually 
by addressing the device as a talker 
and sending that device a serial-poll 
enable command. This constitutes 
one of the bus commands a controller 

Once the controller has 

configured the bus, It 

takes no part In 

subsequent 

transactions until 

reconfiguration is 

desired. 

can send when it asserts ATN. Using 
the serial poll, the controller can ob- 
tain 8 bits of status information from 
the addressed device. The controller 
then sends a serial-poll disable com- 
mand to the device, returning it to 
data mode. 

Serial polling's advantage lies in the 
fact that 8 bits of poll information 
are obtained from each device polled. 
One bit can be used to indicate 
whether or not the device is re- 
questing service. The remaining 7 bits 
are available for other purposes. A 
disadvantage of the serial poll is 
speed. Each device on the bus must be 
polled in turn, since more than one 
device may be requesting service. 

A faster method of polling is the 
parallel poll. The parallel poll is per- 
formed when the active controller 
asserts both ATN and EOI. Up to 8 
devices may respond, each on a dif- 
ferent data line. The only information 
obtained in a parallel poll is whether 
or not a device is requesting service. 
Since each device has only 1 bit to 
respond with, obtaining further infor- 
mation is impossible. 



You Don't Have to Know 

One of the IEEE-488 standard's best 
features is that a system user doesn't 
have to know any of the information 
presented in this article. The stan- 
dard, if followed by all the manufac- 
turers of the devices put on a bus, 
guarantees that devices can talk to 
each other. This assumes that the 
system builder doesn't violate the 
standard by placing two devices at 
the same address, or by connecting 
two system controllers to the bus. 

What then does the system user 
need to know? The standard does not 
specify the messages and data for- 
mats, both of which depend on the 
application. For example, if a 
voltmeter wants to tell the computer 
that it detects +1.234 volts at its in- 
put, what does it send to the com- 
puter as data? Most computers and 
computer languages prefer ASCII 
characters. HPIB specifies that ASCII 
is to be used. Next, the data format 
must be determined. Will the digits be 
sent most significant or least signifi- 
cant first? Again, most computers 
and languages prefer the digits just as 
you might type them, from most 
significant to least. 

Thus, the voltmeter might send the 
following sequence of characters: 

+ 1.234 <CR> <LF> 

The < CR > and < LF > characters 
stand for carriage return and linefeed. 
These characters are often used as 
message terminators in computer 
communications. <LF> alone is 
usually sufficient. 

The definition of messages and 
message formats leaves the IEEE-488 
standard and enters the realm of 
HPIB. This higher-level implementa- 
tion removes yet another layer of in- 
terface problems from the shoulders 
of the system user. 

Next month, I'll discuss two other 
major types of interface: the BCD in- 
terface, often used when a computer 
receives data from scientific in- 
struments, and the serial interface, 
used to transmit data over a single 
wire. We'll see how each evolved to 
deal with specific problems in com- 
munications. ■ 



208 April 1982 © BYTE Publications Inc 



Circle 409 on inquiry card. 



ANNOUNCING ANOTHER NEW IDEA 

FROM TELEVIDEO. 

THE SMART 910 PLUS. 




Our new ideas have a way of sweep- 
ing the market. In just a few years, 
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(In fact, we use the same high 
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The smart 910 Plus Block Mode 
terminal is our latest innovation. For 
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Another point: since service is a 



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OTeleVided 

TeleVideo Systems, Inc. 

1170 Morse Avenue, Sunnyvale, CA 94086 

800-538-8725 (toll-free outside California) 





910 Plus Features 

► Block mode 

► Off-line editing 

► 10 programmed function codes 

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► Protected fields 

► 5 screen attributes (blink, blank, 
reverse, underline, half intensity) 

► 15 baud rates (50b to 10.2Kb) 

► Gated printer port 

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► Self-test 

► Monitor mode 

► 4 strappable languages 



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ATARI HOME COMPUTERS 



A 

ATAOT 




Texas Instruments 





ATARI 800 
16K . . . $679 
32K . . . $749 
48K... $819 



410 Recorder $76.00 

810 Disc Drive $449.00 

822 Printer $269.00 

825 Printer $629.00 

830 Modem $159.00 

820 Printer $269.00 

850 Interface $169.00 

New DOS2 System $29.00 

PACKAGES 

481 Entertainer $83.00 

482 Educator $130.00 

483 Programmer $57.00 

484 Communicator $344.00 

ATARI HOME COMPUTER PROGRAMS 
Home Office 

CX404 ATARI Word Processor $1 19.00 

CX8102 Calculator $29.00 

CX412 Dow Jones Investment Evaluator $99.00 

CX4109 Graph It, Joystick optional $17.00 

CX4104 Mailing List $20.00 

CX41 15 Mortgage & Loan Analysis $13.00 

CX406 Personal Financial Management System . . . $59.00 

CX4103 Statistics 1 $20.00 

CX8107 Stock Analysis $20.00 

CXL4015 TeleLink 1 $23.00 

Home Study 

CX4101 An Invitation to Programming 1 $20 00 

CX4106 An Invitation to Programming 2 $23.00 

CX4107 Biorhythm $13.00 

Conversational Languages (ea.) $46.00 

CX4121 Energy Czar $13.00 

CX4 1 1 4 European Countries & Capitals $1 3.00 

CX4108 Hangman, Joystick optional $13.00 

CX4102 Kingdom $13.00 

CXL4007 Music Composer $47.00 

CX4123 Scram, uses joystick $20.00 

CX4112 States & Capitals $13.00 

CX4110Touch Typing $20.00 

Home Entertainment 

CXL4013 Asteroids $35.00 

CXL4004 Basketball $27.00 

CX4105 Blackjack $1 3.00 

CXL4009 Computer Chess $33.00 

CXL4012 Missile Command $35.00 

CXL4008 Space Invaders $35.00 

CXL401 1 Star Raiders $42.00 

CXL4006 Super Breakout $33.00 

CXL4010 3-D Tic-Tac-Toe $27.00 

CXL4005 Video Easel $24.00 

Programming Languages and Aids 

CXL4003 Assembler Editor $47.00 

CXL4002 ATARI BASIC $47.00 

CX8126 ATARI Microsoft BASIC $70.00 

CXL4018 PILOT $72.00 

CX405 PILOT $105.00 



ATARI 400 
16K. . . . $329 
32K. . . . $478 
48K. . . . $555 



CX30 Paddle $18.00 

CX40 Joy Stick $18.00 

CX853 16K RAM $89.00 

Microtek 16K RAM $75.00 

Microtek 32K RAM $159.00 

Ramdisk (128K) $539.00 

One year extended warranty $50.00 

THIRD PARTY PROGRAMS 
ATARI Program Exchange: 

Eastern Front '41 $25.50 

Avalanche $15.50 

Outlaw $15.50 

747 Landing Simulation $15.50 

Babel $15.50 

Dog Daze $1 5.50 

Downhill $15.50 

Attack! $15.50 

Blackjack-Casino $15.50 

Reversi II $15.50 

Domination $15.50 

Solitare , $15.50 

Disk Fixer $15.50 

Supersort $1 5.50 

Data Management $1 5.50 

Chameleon $1 5.50 

Instedit $15.50 

Insomnia $15.50 

My First Alphabet $25.50 

Mapware $18.00 

Number Blast $ 1 1 .50 

Family Cash Flow $15.50 

Weekly Planner $15.50 

Bowler's Data Base $13.00 

Banner Generator $ 1 1 .50 



Visicalc $169.00 

Letterperfect (Word Processor) $109.00 

Ricochet $14.50 

Crush Crumble & Chomp (cassette or disk) $24.00 

Star Warrior (cassette or disk) $29.00 

Rescue at Riael (cassette or disk) $24.00 

Datestones (cassette or disk) $16.00 

Invasion Orion (cassette or disk) $18.50 

Mission Asteriod $22.00 

MouskATTACK $31.00 

The Next Step $34.00 

Softporn $27.00 

Wizzard & Princess $29.00 

K-BYTE Krazy Shoot Out (ROM) $39.00 

Protector (Disk 32K) $32.00 

Jaw Breaker (on line disk) - - $27.00 

Ghost Hunter (cassette) $24.00 

Ghost Hunter (disk) . $30.00 

COMING SOON 

PAC MAN (May) $35. CENTIPEDE (June) $35 
CAVERNS OF MARS (April) $32 



TI-99/4A 5359 



PHP 1600 Telephone Coupler 

PHP 1700 RS 232 Accessories interface 

PHP 1800 Disk Drive Controller 

PHP 1u50 Disk Memory Drive 

PHP 2200 Memory Expansion (J2K RAM) 

PHA2100R F Modulator 

PHP 1100 Wired Remote ControiiersfPair 

32K Expansion 

PHP Printer Solid State 

PHM 3006 Home Financial Decisions 

PHM 3013 Personal Record Keeping 

PHD 5001 Mailing List 

PHD 5021 Checkbook Manager 

PHM 3008 Video Chess 

PHM 3010 Physical Fitness 

PHM 3009 Football 

PHM 3018 Video Games I 

PHM 3024 Indoor Soccer 

PHM 3025 Mind Challengers 

PHM 3031 The Atlack 

PHM 3032 Blasto 

PHM 3033 Blackjack amj Poker 

PHM 3034 Hustle 

PHM.3036 Zero Zap 

PHM 3037 Hangman 

PHM 3038 Conned Four 

PHM 3039 Yahtzee 



$179.00 
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$1800 
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$18 0Q 
$22 00 




PRINTERS 



Centronics 739-3 $619.00 

Centronics 7394 $519.00 

Diablo 630 Special $1799 00 

Epson 

MX70 $359.00 

MX80 $469.00 

MX80FT Call 

MX100 Call 

NEC 

8023 $549.00 

7730 Call 

7720 Call 

7710 Call 

Okidata 

82A $499.00 

83A $769.00 

84 . $1129 00 

CitohStarwnter 

F10-40 CPS $1469.00 

F10-55CPS Call 

Paper Tiger 

445G $699 00 

460G . $899 00 

560G $1129.00 

Talley 

8024-7 $1399.00 

8024.L $162900 



HOW TO ORDER: Phone orders invited or send check or money order and receive free shipping in the continental United States PA and NEV add sales tax 

computer mail order west 



Franco 
Hables 
Espanol 



800- 648-3351 

IN NEVADA, CALL (702) 588-5654 

P.O. BOX 6689, STATE LINE, NEVADA 89449 



210 BYTE April 1982 



Circle 108 on inquiry card. 



Whp% HEWLETT 
mJfiM PACKARD 




HP*85 $ 1999 

80 Column Printer $799.00 

HP- 125 $1999.00 

HP-83 $1699.00 

HP-85 16K Memory Module $169.00 

5 V* " Dual Master Disc Drive $1929.00 

Graphics Plotter (7225B) $2079.00 

NEW! HP-87 $1999.00 

Hard Disk w/Floppy $4349.00 

Hard Disk $3440.00 

"Sweet Lips" Plotter $11 49.00 

HP41CV Calculator 
$259 

41 C $189.00 

11C $119.00 

12C. , $129.00 

34 C $117.00 

38C $119.00 

HP-41 Printer $340.00 

HPIL CALCULATOR PERIPHERALS 

IL Modual $104.00 

Digital Cassette $449.00 

Printer/Plotter $419.00 

Card Reader $164.00 

Optical Wand $99.00 

CALL FOR SOFTWARE INFORMATION 



(icommodore 

BUSINESS MACHINES 

CBM 8032 

s 1069 




XEROX, 



Xerox 820 

System I 5V«." $2450.00 

System II 8" $2950.00 

CPM 5V'4 " , $169.00 

Word Processing $429.00 

Super Calc $269 00 

CALL FOR MORE INFORMATION 



SOFTWARE 

Word Pro 5 Plus $319.00 

WordPro3 Plus .... $199.00 

WordPro4 Plus $299.00 

Commodore Tax Package $589.00 

Visicalc $169.00 

Medical Billing $449.00 

The Source $89,00 

OZZ Information System $289.00 

Dow Jones Portfolio $129.00 

Pascal $239.00 

Legal Time Accounting $449.00 

Word Craft 80 $289.00 

Power $79.00 

Socket-2-Me $20.00 

Jinsam $Call 

MAGIS S Call 

The Manager $209.00 

Softrom $129.00 

Real Estate Package $799.00 

BPI Inventory Control $319.00 

BPI Job Costing $319.00 

BPI Payroll $319.00 

BPi General leoqe' $32900 

Creative I SAM $79.00 

Creative General Ledger $229.00 

Creative Accounts Receivable $229.00 

Creative Inventory $229.00 



Vic 6 Pack Program $44 00 

VIC1530 Commodore Ddtassetie $69 00 

VIC1540 Disk Drive $499 00 

VIC1515 ViC Graphic Punier $339.00 

VIC1210 3K Memory Expander $32 00 

VIC i HO 8K Memory Expander $53 00 

VIC101 1 RS232C Terminal interface $43 00 

VICH12VIC IEEE 488lnlerface $86 00 

VIC1211 VIC 20 Super Expander $53 00 

VT232 VlCTerm I Terminal Emulator $9 00 



4032 $969.00 

4016 $769.00 

8096 Upgrade Kit $399.00 

Super Pet $1599.00 

2031 $529.00 

8050 $1299.00 

4040 $969.00 

8300 (Letter Ouality) $1799.00 

8023 • ' $769.00 

4022 $599 00 

Petto IEEE Cable. $37 00 

IEEE to IEEE Cable .'.'.'.'.'.' $46 ; o o 

Tractor Feed for 8300 $240,00 

8010 Modem $229 00 




VIC 20 $259 

COMPLETE 



VIC1212 Programmers Aid Cartridge 

VIC1213 VlCMON Machine Language Monitor 

VIO901 VIC AVENGERS 

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VIC1906 SUPER ALIEN 

VIC1907 SUPER LANDER 

VIC1908 DRAW POKER 

VIC1909 MIDNIGHT DRIVE 

VT106A Recreation Pack A 

VT107A Heme Calculation Pack A 

VT164 Proarammabie Character/Grameqraphics 



$45 00 
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$12.00 



New VIC Software 



Household Finance $27.00 

VIC Games $19.00 

VIC Home Inventory $1300 

VIC Rec/Ed II $13.00 

VL101 Introduction to Computing $19.00 

VL102 Introduction to BASIC Programming $19.00 

VM1 10 VIC 20 Programmers Reference Guide . . . $15.00 



Terminal $13.00 

UnWord... , $13.00 

Grafix Menagerie $11.00 

VIC PICS $15.00 

Ticker Tape $13.00 

Banner Headlmer ' . . . $13.00 

RS 232 $39.00 



Modems 



Novation Auto $239.00 

Cat , $169.00 

Cat $159.00 

Hayes 

Smart $239 00 

Livermore Star $1 19.00 



Terminals 

Televideo 

910 $579 00 

912C $699.00 

920C $749.00 

950 $939.00 

Call for computers 

ZenilhZl9 $749 00 

Adds $549 00 



Monitors 

Amdex 12" B&W . $139.00 

12" Green 1149.00 

13" Color . $349 00 

Sanyo 12" B&W $259.00 

12" Green .... $269 00 

13" Color $449.00 

Tl 10" Color ......... $349.00 



Above are cash prices, add 3% for Master Card and Visa purchases 



computer mail order 
800-233-8950 

IN PA. CALL (71 7) 327-9575 

477 E. THIRD ST., WILLIAMSPORT, PA 17701 




Patricio 

Hables 

Espanol 



Circle 108 on inquiry card. 



BYTE April 1982 211 



User's Column 



The Osborne 1, 

Zeke's New Friends, 

and Spelling Revisited 

A seasoned computer user looks at new products and updates. 



Jerry Pournelle 

c/o BYTE Publications 

POB 372 

Hancock, NH 03449 



"It's the great software drought," 
said my mad friend Mac Lean. "Have 
you noticed? There's no good new 
software. Just updates and revisions 
and new versions of old programs." 

"Not true," I protested. "Just 
yesterday I got Sorcim's Supercalc." 

"Sure. The CP/M version of a 
year-old Apple program. Good stuff. 
Useful. Excellent. But not new." 

"Hmm. Maybe you're right. Well, 
at least they're improving old pro- 
grams. I have an update for Spell- 
guard." 

"Aha," said my mad friend. "Tell 
me, are you still using Spellguard?" 

"Yep." 

"Thought you had a whole mess of 
new spelling programs." 

"I do. Here's one of them." I held 
up Microproof . "But I don't use them. 
Better to stay with Spellguard. Espe- 
cially now, with its improved dic- 
tionary." 



Which is true. I suppose it comes as 
no surprise that I am very interested 
in spelling and editing programs. 



After all, words are 

my business . . . 

I need 

good spelling 

programs. 



After all, words are my business, and 
I am, according to Robert Heinlein, 
one of the "wurst spellurs" he has 
ever encountered. I need good spell- 
ing programs, and I have to use them 
a lot, which means I'm interested in 
speed and convenience, which is why 
I stick with Spellguard despite its lack 
of certain features. 

Example: in my previous Spell- 
guard review [see November 1981 



BYTE, page 449], I said "it corrects 
spelling." BYTE's editors, in the in- 
terest of accuracy, changed that to 
"finds and marks spelling errors." 
Other programs, such as Microproof, 
correct spelling errors. All true, but 
irrelevant. The job to be performed is 
spelling correction, and Spellguard 
does that [also see "Five Spelling- 
Correction Programs for CP/M- 
Based Systems" by Phil Lemmons, 
November 1981 BYTE, page 434]. 

Example: Microproof's specifica- 
tions make it sound far better than 
Spellguard. (Let me call them MP and 
SG from here on.) MP has a 50,000- 
word dictionary compared to SG's 
20,000. MP knows about plurals and 
prefixes; you can tag a word as a 
noun or an adjective or an adverb, 
and MP will take the root and add 
suffixes and prefixes and such like. 
Finally, MP lets you correct the word 
and will then go off and put that 



212 April 1982 © BYTE Publications Inc 



Circle 25 on inquiry card. 



word in your text file, while all SG 
does is mark it for you to go fix using 
your standard editor. 

Sounds great, doesn't it? 

The trouble comes when you use it. 
That's presuming you even try; the 
manual was enough to cause me to 
leave MP in the box for over a 
month. 

(Digression. The Microproof 
manual, which, according to its in- 
terior blurbs, was written by "an 
acknowledged expert in the field of 
programmed learning," is a general- 
purpose thing, intended for several 
versions of the program; and because 
it's never made clear what version 
you have, it's unutterably confusing. 
And that sort of thing happens all the 
time. 

TO ALL SOFTWARE PUBLISH- 
ERS: look, if you want to charge $100 
and more for programs, you can 
darned well furnish a manual tailored 
for each program!) 

In Microproof 's favor, I have to 
say that when you actually start using 
the program — as opposed to trying to 
figure out how to use it — it gets sim- 
ple. The prompts are clear and the 
procedures are simple. 

But it's slow. Ye gods, it's slow to 
work with. Instead of leaving the in- 
structions on the screen and using the 
same entry line over and over again, 
as SG does, MP clears the screen and 
rewrites it, prompts and instructions 
and all, for each word it didn't 
recognize — dozens of them. Eventual- 
ly you get through that, after which 
MP reads your text file and corrects 
it. That, however, takes about as 
long as it would have taken to load 
your editor, bring in the file, and 
search for the marked blocks; and 
because, if you're like me anyway, 
you'll want to see the corrected text 
and possibly reformat it before print- 
ing it and sending it out, you'll have 
to load the editor and text file 
anyway. 

Now about those prefix and suffix 
"features." I suspect they have some- 
thing to do with the fact that I CAN- 



NOT get Microproof to believe that 
"index," "kilobyte," "milestone," 
"undoubtedly," "Unix," and "auto- 
matic" are words. I went through my 
third "User's Column" (the one re- 
viewing Spellguard!) as a test file four 
times and each time I patiently 
entered those words into the MP dic- 
tionary; and next pass I got them read 
back to me as misspellings. 

(To make the test fair, I used 
Microproof on this text too, and not 
only won't it admit that the above are 
words after two passes, but until I 
entered it, it didn't recognize Micro- 
proof! Meaning, I would suppose, 
that they didn't use the program on 
their own manual. If they won't use 
it, why should anyone?) 

There's worse. MP doesn't know 
about apostrophes. It gives me the 
"weren" of "weren't" as a candidate 
word. It does the same with "doesn." 
And if you use dashes! Spellguard 
understands dashes and hyphens, but 
if you have a double hyphen (which 
represents a typeset dash) in your 
text, SP thinks that is two separate 
words and examines each. Micro- 
proof offers me the "program — as" 
and "it — it" that I used above as can- 
didate words. If you use many dashes 
in your text, you will, I assure you, 
go quite mad after about the third 
pass Microproof makes at your text. 

Finally, Microproof doesn't know 
much about error handling. It takes 
forever to go through a 6500-word 
text file; and if you've left insufficient 
space on your disk for the original file 
plus a backup (.BAK) file, then when 
Microproof finds that out, it simply 
dumps the job, leaving you either in 
CP/M or the monitor, depending on 
just how confused MP got. Either 
way, you've lost all the work you just 
did. 

So. Microproof is a heroic effort 
to make a more convenient spelling 
program. They tried to do right. The 
concept was good. The execution, 
though, leaves something to be de- 
sired. 

There's a version geared to work 



CALCULATOR 
EPROM MEMORY 

for 

Hewlett-Packard 
41C/CV 




EPROM memory with custom 
keyboard overlay also produced by 
DDS. 



• Plugs into any port of the 
HP-41C or -41CV calculator. 

• Provides non-volatile 
program storage formatted 
and accessed as if it were a 
custom HP calculator ROM. 

• Uses standard 2716, 2732, and 
2764 EPROMs (Eraseable 
Programmable Read Only 
Memory). 

• Holds calculator programs in 
4K, 8K, or 16K segments. 

• Completely portable and 
requires no external power 
supply or battery. 

USES 

• Field testing of software 
before the ROM is 
manufactured. 

• Low volume production runs 
where a custom ROM would 
be prohibitively expensive. 



$299.95 




DALLAS DEVELOPMENT SYSTEMS 

7410 Stillwater Drive 

Garland, Texas 75042 

[214)238-1776 



April 1982 © BYTE Publications Inc 213 



User's Column. 



with either Electric Pencil or Scripsit 
for the TRS-80 Model I (and III) and 
TRSDOS. (Microproof has recently 
fixed most of the problems, partly 
because I sent a preliminary copy of 
this review to them. See next column 
for details; Microproof is now com- 
petitive with Spellguard.) 

Which, incidentally, has been great- 
ly improved. Now there's an explicit 
way to remove misspelled words er- 
roneously entered into the dictionary. 
Also, the updated version packs the 
dictionary into half the space and runs 
about twice as fast. It took me just 



about an hour, using Microproof, to 
shape up a 6500-word column; with 
new Spellguard, the whole job (in- 
cluding looking up and entering into 
the program's dictionary about 100 
new words) took fewer than 20 
minutes. 

The Spellguard documentation re- 
mains excellent, as clear and precise as 
anything I've seen in the field. Still 
highly recommended. 

Zeke's New Friends 

A few minutes ago, Arthur C. 
Clarke called me from Sri Lanka. (He 



lives there. I think the nation has de- 
clared him a national treasure; I know 
that when Robert Heinlein visited him, 
Dr. Clarke was able to arrange for a 
Sri Lanka air force helicopter to take 
Robert about the country.) 

Arthur had seen some of my com- 
puter articles, and what he wanted to 
know was what everyone nowadays 
wants to know: what do you buy for a 
first computer? 

Unfortunately, the answer is, it 
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User's Column. 



I was talking with Ezekial, my 
friend who happens to be a Cromemco 
Z-2. 

"I'm getting old, boss," he said. 

"You were built in 1977!" 

"Yeah. In this business, that's old. 
Look, we've written five books and 
dozens of columns and hundreds of 
letters. I do all your taxes and account- 
ing. I compile all your programs, in 
twenty languages. I even play games 
with you." 

"OK, OK, so what do you want?" 

"Some rest. A bit of help. Look, I'll 

* make you a deal. I'll help you write 

books, same as always, but you go get 

something faster, something new, to 

do all that compiling and calculating." 

"Never thought I'd hear you say it," 
I said. "Better is the enemy of good 
enough. And you're plenty good 
enough!" 

"Could use help, boss. Big responsi- 
bility, being the only computer around 
here. Especially now that you're so 



busy with the Citizen's Advisory 
Council on National Space Policy stuff 
and the L-5 Society." (Plug: if you're 
interested in helping the space pro- 
gram, join L-5. It's $20 a year; send fee 
to L-5 Society, 1060 E. Elm, Tucson, 
AZ 85719. Contributions tax deducti- 
ble within the framework of the law. 
Secretary this year: Jerry Pournelle.) 

"What happens," Zeke continued, 
"if I get sick?" 

I thought about it a long time. He's 
right, of course. He is getting old; and 
he's utterly spoiled me. I can't con- 
ceive of writing without a computer. I 
live in terror that Zeke is going to quit 
on me. Actually I don't; he's rarely 
given cause for alarm. A couple of 
times in the early days we had glitches 
that brought Tony Pietsch out— 
always in the middle of the night; nice 
chap, Tony — but they always got 
fixed without having to take Zeke 
away. But not long ago something 
gave out in the disk power supply, 



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keeping Zeke shut down for nearly a 
week. True, I was out of town at the 
time, but it could have been a disaster. 

I needed a second computer. But 
what? 

In the middle of the dilemma, Adam 
Osborne sent me his new Osborne 1. 

That darned near solved my prob- 
lem. Osborne's machine is good. The 
first models had some faulty charac- 
teristics, but Adam is an honorable 
man — and also smart enough not to 
risk his reputation by sharp practices. 
They're planning retrofits to take care 
of all major difficulties and most 
minor ones. 

The worst of these was the shift 
lock, which was worse than useless. 
Then, too, with that tiny screen you 
needed smooth vertical scrolling (it 
already had good horizontal scroll- 
ing). There have been some other 
minor annoyances, but as I said, 
Adam's been fixing them. The new 
Osborne 1 computers — out by the 
time this is published — will incor- 
porate the improvements, including 
true three-key rollover and a decent 
shift lock, and various other fixes. 
Those who have already bought the 
machines will be able to get them 
retrofitted absolutely free. 

One thing I thought would be a pain 
turned out not to be. That's the tiny 
video screen. Adam has sent me his 
larger video monitor, which you can 
connect to the Osborne 1 with a cable, 
but I find I don't use it. The little 
screen turns out to be just at the right 
focal distance when I sit at the console; 
and for someone like me, who wears 
bifocal glasses, that's a real boon. 

I carried the Osborne 1 out to Cal 
Tech's Jet Propulsion Laboratories for 
the Voyager 2 encounter with Saturn. 
There were over a hundred members 
of the science press corps packed into 
JPL's Von Karman Center (the press 
facility). Most had typewriters. One 
or two had big, cumbersome word 
processors. At least one was a terminal 
connected through a network to the 
parent system in New York. Nobody 
had anything near as convenient as the 
Osborne 1, which is quiet and fast 
responding. 



216 April 1982 © BYTE Publications Inc 



How To Sell 
More Software 




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If you're an individual software author or a software 
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How to publish attractive manuals that speak well 
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Schedule: Chicago May 21 

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User's Column. 



Everyone came to look at it. "How 
can you stand that tiny screen?" asked 
Eric Burgess, senior science correspon- 
dent present. (Eric's the chap who first 
thought of the message plaque to be 
attached to the space probes. I was 
there when he got the idea. But that's 
another story.) He stared over my 
shoulder. "It's so small." 

"Try it," I invited. I got up to give 
him my place and watched as he 
realized that when you're sitting at the 
machine you can read it at least as 
easily as you can a book. Before the 
encounter was over, a dozen science 
writers were ready to go buy an 
Osborne 1. 

I also took it to the meeting of the 
Citizen's Advisory Council on Na- 
tional Space Policy (which I chair) and 
used it to take notes during the meet- 
ing. It was amazing: I was able to type 
notes and suggestions and ideas into 
the Osborne 1 without disrupting the 



meeting at all. The Osborne 1 is quiet 
and efficient and not at all distracting. 

In other words, I like the Osborne 1. 
You can't beat it for the price, under 
$2000 bucks with over a thousand 
dollars' worth of software. An 
Osborne and an Epson printer will put 
you in the computer/word-processing 
business cheaper than anything I can 
think of, and the Osborne 1 is a real 
computer, using the CP/M operating 
system and adult software like Word- 
star and Supercalc and dBase II; it's 
not a toy. 

So. For those who haven't a lot of 
money to spend and want to get going 
in computers, I don't hesitate to re- 
commend the Osborne 1 — as a first 
system. However, it is a limited sys- 
tem. It wasn't designed for lots of ex- 
pansion capabilities, and it's never go- 
ing to be able to use them. But as a 
first machine, it has a lot going for it, 
and not just the price. 



When I first got the Osborne 1, I 
thought I'd solve one of my problems, 
which is, how can I have someone 
entering letters and files and old books 
while I'm using Ezekial? I certainly am 
not going to have a multiuser micro- 
computer, which defeats the whole 
concept of decentralized computing. 
Our TRS-80 Model I with Omikron's 
CP/M conversion will do the job, but 
it's often in use as the boys check out 
new games and educational stuff; 
worse, the TRS-80 keyboard is plain 
awful, driving my editorial associates 
crazy. Even the boys get weary of it. 

No, I needed a second machine, 
with a good text editor. Aha, says I. 
I'll use the Osborne 1. Of course the 
Osborne 1 has only 5V4-inch disks, 
and Ezekial has 8-inch disks, but that's 
all right. The TRS-80 has both 
5y4-inch and 8-inch Lobo disks, and 
those work fine, and under CP/M we 
can copy files from the little disks to 



SB-80 




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218 April 1982 © BYTE Publications Inc 



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Every issue of BYTE is filled with 
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User's Column. 



the big disks using the PIP utility rou- 
tine. So all we have to do is to take a 
disk from the Osborne 1 to the TRS-80 
and. . . . 

It doesn't work. The Osborne disk 
format is different from the Omikron's 
format. And, talking to Mike Mc- 
Culloch of Osborne Computer Cor- 
poration, I find there's no easy solu- 
tion to the problem. If there were a 
"standard" 5y4-inch disk format (as 



there is a standard for 8-inch disks — 
the IBM single-density soft-sectored 
format), then Osborne would use it. 
Indeed, when Osborne goes to double 
density for disks, it'll use the new IBM 
5y4-inch double-density format. But 
Osborne can't use a standard until one 
exists. 

Which means that the only way to 
get files from the Osborne 1 to Zeke is 
to send them out the Osborne l's serial 



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port. Now the Osborne 1 has such 
ports, both RS-232C and modem 
ports, so that's not impossible, and 
nowadays Osborne will furnish you 
with software to accomplish the job 
(well, to accomplish the Osborne 1 
end of the job; obviously you'll have 
to have appropriate software on the 
other end to catch what the Osborne 1 
is pitching). 

Moreover, the Osborne 1 format 
may yet become the "standard" for 
5V4-inch single-density disks. Accord- 
ing to McCulloch, the major software 
houses have been given copies of the 
specifications as well as an Osborne 1 
machine and have been invited to offer 
software on disks readable by the 
Osborne 1; Adam Osborne has no in- 
tention of cutting his users off from the 
vast marketplace of CP/M software. 
Just the opposite. 

So. By now you get the idea. The 
Osborne 1 is as good an entry-level 
system as I have seen. The only prod- 
ucts that come close to it are the new 
IBM Personal Computer and the 
Heath/Zenith H-89, and both come 
with only one disk drive and very little 
software at a price a good bit higher 
than the Osborne 1. 

I did not, however, recommend the 
Osborne 1 to Arthur Clarke; and I 
never seriously considered it as the 
new machine Zeke wanted me to set 
up as his assistant. It's not that I won't 
keep mine and use it as a portable for a 
very long time; but I need more ma- 
chine than can be bought for $2000, 
and so does Arthur Clarke. 

Candidates 

"Maybe," I said to my mad friend, 
"maybe I'll get an H-89. I can get it 
with CP/M and a printer and get a 
company to fit a case for it. I see ad- 
vertised a board that will let it talk to 
8-inch disks, which will solve the 
problem of communicating with Zeke. 
I can end up with a portable." 

"Good thinking, as long as you 
think of it as a spare. Your real ma- 
chine needs an expandable bus." 

"True. But for a portable. ... In 
fact," I said in boyish enthusiasm, 
"maybe I'll get it as a kit and build it so 



220 April 1982 © BYTE Publications Inc 



Circle 369 on Inquiry card. 





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User's Column. 



I can understand the machine." 

"Sounds like about as much fun as 
an appendectomy/' said Mac Lean. 

I can always count on him to prick 
any silly bubbles like that. 

In the middle of all that came 
another emergency. Dr. Stefan T. 
Possony, my long-time friend, asso- 
ciate, and collaborator, decided to get 
a computer. He'd seen Ezekial, and he 
wanted him. Or one like him. 

Not long ago the solution to the 
problem would have been simple. 
We'd simply hand money to Tony 
Pietsch of Proteus Engineering, he 
would produce an updated clone of 
Ezekial, and all would be well. Unfor- 
tunately, Tony's in great demand as a 
consultant and has just about gone out 
of the systems-integration business. 

So, what to get? For Stefan, and for 
me. 

It didn't take much research to come 
to several conclusions. First, a profes- 
sional system ought to have 8-inch 
floppy-disk drives. The little disks are 
fine for entry-level learning systems, 
but they're just not solid enough — and 
won't hold enough files — for profes- 
sional work. Second, the system has to 
use Digital Research's CP/M operating 
system. With Xerox, Wang, and DEC 
(Digital Equipment Corporation) com- 
ing into the field, CP/M is more than a 



de facto standard, it's a necessity. 
Third, the S-100 bus (in a quiet version 
and built to the IEEE standard, if at all 
possible) is still the most versatile 
small-computer system going and will 
be for some time. An S-100 with a Z80 
processor is the way to go. 

"But why not the new IBM Per- 
sonal Computer?" one of my sane 
friends asked. "It has an expansion 
bus. Not the S-100, true, but a bus. 
And CP/M-86, and IBM maintenance 
and — " 

And 5 Va -inch floppy disks, which 
even with IBM behind them are going 
to be a problem. Furthermore, as of 
right now (fall, 1981) the local people 
selling the IBM know nothing about 
software availability, although with 
Microsoft's support I expect that to 
change by the time you read this. 

The IBM may sweep the field; 
heaven knows it's a handsome enough 
unit. I learned to write with an IBM 
typewriter keyboard, and I've found 
few computer keyboards up to the 
Selectric — and the new IBM computer 
keyboard is even nicer. Indeed, I'm 
thinking seriously of getting an IBM. 
But for all of IBM's prodigious reputa- 
tion, it hasn't a lot of experience with 
small computers. Until it gains some, I 
think I'll wait. Besides, IBM Personal 
Computers weren't available back last 



summer when Stefan wanted his ma- 
chine. 

So. What to get? And how to install 
it long distance? That really presented 
a problem. Possony knows nothing 
about computers, and there aren't too 
many off-the-shelf S-100 systems. I 
could get a Vector; although I've no 
direct experience with them, people I 
trust tell me they're excellent. 

But then I remembered: I have a 
good friend, Dr. Colin Mick (Decision 
Information Services, POB 5849, 
Stanford, CA 94305, (415) 327-5797), 
in the Stanford area, where Dr. 
Possony lives. A quick phone call, and 
Colin foolishly volunteered to help 
Stefan. It turned out well. Colin in- 
stalled a CCS (California Computer 
Systems) system with a Heath/ Zenith 
Z-19 terminal in Stefan's house. He 
chose CCS because that's what he has, 
and he knows some of the CCS design 
team; the result has been so successful 
that Colin is now much in demand as a 
small-systems consultant. 

Another result is that Possony, 
already one of the world's most pro- 
lific writers on foreign affairs and in- 
ternational politics, has more than 
doubled his output. He loves his new 
system; and when you consider that 
Stefan is a Viennese intellectual, who 
got his Ph.D. the year after I was born 



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User's Column. 



and who knows very little about ma- 
chines, that's quite a statement. It's 
also a great testimony to Colin's pa- 
tience and instructional capability. 

Decision Information Services got 
one thing out of it. They're writing a 
book for first users. Given Colin's 
understanding of computers and 
Stefan's ability to ask penetrating 
questions, I wouldn't be surprised to 
see it become the best book ever done 
on the subject. 

So. That was one candidate. CCS 
seemed a very good system, and cer- 
tainly a lot of them are being sold. 

Tony, meanwhile, was putting to- 
gether a Godbout (Compupro), with 
the dual Z0S5/S0W 8-bit/16-bit capa- 
bility. And Richard Frank, of Sorcim, 
had told me he uses Godbout units for 
all his development work because he 
considers them the most rugged and 
reliable systems available. 

I stewed for a while, then called Bill 
Godbout. The result is that Zeke's big 
brother is sitting in the next room. 

Understand that I've nothing against 
the CCS system. Quite the opposite. 
It's an excellent system and one of 
those I recommend. But the Godbout 
is more than that. It's built like a 
Mack truck. You couldn't hurt it with 
a nine-pound sledge. When it comes to 
rugged reliability, Godbout is the way 
to go for my money; and Tony says 
the bus is the quietest he's ever worked 
with. 

What we have is the Godbout 
(Compupro) S-100 box, Godbout's 
disk controller and inter/facer board, 
his 8085/88 processors as well as the 
Z80 processor (obviously you can't 
use both at the same time), 128K bytes 
of Godbout memory, and his system 
support vectored interrupt board. The 
disk drives are Qume double-sided 
double-density 8-inch drives with a 
Vista box and power supply. 

I confess to being a bit worried 
about double-sided double-density 
disks. Asking for trouble, I thought; 
but I was wrong. With the Godbout 
controller and Qume drives my disks 
are as quiet as the Icom drives ever 
were — and they're wonderfully fast. 
; We're still shaking down the God- 



bout system. When it's all done and 
checked out, I intend to get another set 
of Qumes and install them in Zeke. 
More on both the Qumes and the 
Godbout another time. 

WRITE Arrives 

So. Zeke has two new friends, the 
Osborne and the Godbout; and he's 
about to get new disk drives. 

There's more happening here at 
Chaos Manor. Tony Pietsch's new text 
editor, WRITE, is done at last. I'm us- 
ing it to do this column. 

Write is much like Electric Pencil 
without bugs. It ought to be: back 
when I started writing with com- 
puters, Pencil was the best editor 
around, and we put together a system 
to work with it. Unfortunately, Pencil 
has bugs. One, the tendency to drop 
letters at the ends of lines, is 
notorious. Another is a needlessly 
complex handshaking routine to cou- 
ple Pencil to the Diablo (that one's so 
severe we use a special CP/M BIOS 
[basic input/output system] reserved 
just for Pencil). There are other prob- 
lems, and over the years my partner 
Larry Niven and I have been making 
lists of Pencil's faults. We've also made 
notes on just what we'd like in a text 
creation editor, features that Pencil 
never had. 

Anton (Tony) Pietsch has been col- 
lecting those notes and writing an 
editor to fit. In these columns and in 
pieces for BYTE's companion onCom- 
puting, now called Popular Comput- 
ing, I've several times announced that 
it would be ready "real soon now." I'm 
happy to say that this time it's here 
and it works. 

But this version will only work for 
systems with memory-mapped video 
display. For the Godbout that's 
simple enough: we use an Ithaca 
IA-1100 Write-Only Memory video 
output board addressed to hexa- 
decimal address FC00, and a separate 
keyboard. The system normally oper- 
ates through an H-19 terminal, but it 
can be rigged up to think that Ezekial 
is its terminal — or to work with my 
regular keyboard, putting the output 
up on my big 15-inch monitor screen 



224 April 1982 © BYTE Publications Inc 



LOGO 



Language of the 80's 

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The author introduces programming techniques through Turtle Geometry — a series of 
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m 



CD 



User's Column. 



through the IA-1100. This is one of the 
advantages of an S-100 bus system. 
You can configure it to do nifty things 
like that. 

Anyway, back to WRITE. Why is it 
so good that I'm willing to overlay 
some of my memory with video and 
have special boards, and such like? 
Can it be as good as all thatl 

It depends on what you want an 
editor for. I have no doubt that some 
of the really fancy "window-type" 
editors based on the MIT EMACS 
editor or built around special display 
boards may be more elegant in theory. 
Moreover, Micropro's Wordmaster 
remains, in my judgment, the best 
programming editor ever invented. 

But for just sitting down and writing 
I want something as nearly invisible as 
can be made. I don't want to think 
about my editor. I don't want it to nat- 
ter at me about line numbers and col- 
umn numbers and such. I don't want it 
drawing funny lines across the screen 
to mark the ends of pages. I don't 
want it clicking disks at me, or run- 
ning out of disk space and giving me 
no chance to change disks. 

And if I want to pull some text in 
from another disk somewhere, I want 
to be able to do that. If I want to write 
some text out onto a safety disk, I 
want to be able to do that, too. If I 



want to print out my text on paper, I 
don't want to have to double-space it 
on the screen in order to get it double- 
spaced on the manuscript. 

And for heaven's sake, if I fiddle 
around with a paragraph and snip off 
words here and add some there, I 
don't want to have to reformat the 
text! My editor should do that for me, 
silently, easily, automatically. 

And that's what I have in WRITE. A 
nearly invisible editor. Add to that a 
really powerful macro-command 
capability, with loops and global 
searches and deletes, and an ability to 
link disk files so that the program 
treats them as if they were one enor- 
mous file. 

Add it all up and it's WRITE, 
Writers' Really Incredible Text Editor. 
I'm sure I'll have more to say about it 
another time. Meanwhile, if your sys- 
tem will run Electric Pencil under 
CP/M, it will run WRITE, which will 
be able to read all your old Pencil files. 
(It will also read Wordstar and Word- 
master files.) If you do creative writ- 
ing, you'll appreciate WRITE a lot. 
Highly recommended. 

One more note on text editors. Peo- 
ple ask me what I have against Word- 
star. My answer is simple. Lots of 
friends use Wordstar, and I use it on 
the Osborne. It's a good editor to run 



on a terminal. Like all editors on ter- 
minals, the scrolling is ugly, but that's 
not Wordstar's fault. Micropro Inter- 
national continually works to add fea- 
tures and capabilities, and it's done 
well. 

What Micropro can't do is correct 
the basic deficiency, which is the two- 
keystroke command system with 
delay in between strokes. When I want 
to delete a line, or scroll, or go from 
the beginning to the end of the text, I 
want to do that right now. I don't 
want to hit control-Q, then remember 
that "c" takes me to the end of the text 
unless I've hit the space bar in be- 
tween, in which case — 

Nor do I want a bunch of prompts 
and lines and menu items on the 
screen. OK, so you can suppress those 
menu descriptions — provided, of 
course, that you remember all the 
command items. But you won't. 
Wordstar has too many features. Now 
that would be all right if you could ig- 
nore most of them, but you can't. 
They take up single-stroke control 
characters so that there are none left 
for the functions you want to have 
happen fast. In contrast, WRITE's ap- 
proach is to use the single-strokes for 
such things as toggling insert /delete 
modes, opening a hole in the text for 
long insertions, and marking blocks of 



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226 April 1982 © BYTE Publications Inc 




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Prices & availability subject to change without notice 



User's Column. 



text and moving them; and, much as 
Wordmaster does, it allows you to use 
the macro-command capability for all 
the really complicated stuff. WRITE 
also has the menu available at any 
time : simply hit Escape and you'll see a 
whole list of instructions, pages of 
them if you like. But you don't see 
them unless you want to. I wish 
Wordstar had taken that approach. 

I do recommend Wordstar for some 
purposes. First, it works on a terminal. 
Because it knows where the ends of 
pages are, it can do indexing. It for- 
mats on screen; what you see is what 
you get, an intolerable disadvantage 
when what you want is a simple 
double-spaced manuscript (who wants 
his on-screen text double-spaced?) but 
a real boon if you're publishing a 
newsletter or other matter requiring 
holes for illustration. It has a good 
mail-merge utility. If you can use any 
of those features, Wordstar is the only 
program that has them. 

Incidentally, there are a couple of 
candidates for Wordstar's crown, one 
of them being MINCE (acronym for 
MINCE Is Not Complete EMACS) 
which emulates EMACS, the MIT 
(Massachusetts Institute of Tech- 
nology) full-screen editor and is cer- 
tainly the best editor if you want to 



write LISP programs. MINCE works 
on terminals (but not with memory- 
mapped video; at least I've never been 
able to get it running on Zeke). Now 
that the Godbout with the H-19 is up 
and running, we'll have a more 
thorough report. But when it comes to 
creating text, you won't beat WRITE. 
Or so say I. 

muSimp / muMath 

Some time ago, I got a copy of 
muSimp/muMath from the Soft Ware- 
house. Marketing of these programs 
has since been taken over by Micro- 
soft, which has probably enhanced the 
documentation — at least it usually 
does. 

There's nothing quite like muMath 
[For another review see 'The muSimp/ 
muMath-79 Symbolic Math System" 
by Gregg Williams, November 1980 
BYTE, page 324]. The basic concept 
comes from MACSYMA, the sym- 
bolic-algebra programs continually 
under development at MIT's computer 
laboratories, which run on the DEC 
PDP-10. Obviously, there is no way 
to put the full power of a PDP-10 into 
a microcomputer — although the God- 
bout 8085/88 comes closer than I 
would have thought possible a few 
years ago. 



MuMath consists of a core plus a 
whole series of auxiliary routines. The 
programs are written in LISP, but you 
don't have to know LISP to use them. 
(It would help, though. Boy would it 
help.) MuSimp is another package of 
routines which will also work with 
muMath. Together they will do a sur- 
prising lot of useful work. You could, 
for example, write a Visicalc in 
muSimp/muMath, and I suspect it 
would work quite well . There are also 
examples of how to write a database 
system using them. 

In other words, muSimp/muMath 
have a lot more power than appears 
on the surface (or, indeed, is hinted at 
in the advertisements). 

Their primary purpose, though, is 
to do symbolic math. And here I have 
to confess a fault. When I first got 
muSimp/muMath, I tended to com- 
pare them to MACSYMA, and of 
course these programs written for 8-bit 
microprocessors came up wanting. 
How could they not? What I should 
have done was find someone who 
never had access to MACSYMA and 
ask what she thought of them, and 
recently that's what I did. 

"Wonderful," said my lovely friend. 
'Tve never even suspected you could 
do things like that on a computer. 



■ 












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on special request. 

$1 500 

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1036 Los Altos Avenue 

Los Altos, CA 94022 

(415)941-8748 



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228 April 1982 © BYTE Publications Inc 



THE 
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STARTING YOUR OWN 
MICROCOMPUTER BUSINESS 

Starting your own microcomputer business is easy if you 
know the right steps to take. Two volumes of the new book 
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Carpinteria, CA 93013 Ph. (805) 684-1489 

Please send the following book(s) by return mail. I 
understand if I want to return them for any reason within 30 
days of receipt, I can do so and get a prompt full refund. 

□ Your Fortune In The Microcomputer Business 
Vol. I, Getting Started, $20.00. (Postpaid) 

□ Your Fortune In The Microcomputer Business 

Vol. II, Growth, Survival and Success, $20.00. (Postpaid) 
Calif, residents please add $1.20 each sales tax. 

Name 

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Enclosed is 

Card# 

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Signature 



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_or charge my MasterCharge D or Visa D 



MCInterbank # 



- © 1982 Wildfire Pub. 



User's Column. 



Items Reviewed 




Ashton-Tate 




Suite 1510 




3600 Wilshire Boulevard 




Los Angeles, CA 90010 




(213) 204-5570 




WRITE 




(Writers' Really Incredible Text Editor) 


$395 


California Computer Systems 




250 Caribbean Drive 




Sunnyvale, CA 94086 




(408) 734-5811 




Model 2210AS-100 


$2350 


Compupro-Godbout Co. 




Oakland Airport, CA 94614 




(415) 562-0636 




8085/8088 Dual Processor 




6 MHz 


$425 


8 MHz 


$525 


Cornucopia Software 




POB 5028 




Walnut Creek, CA 94596 




(415) 524-8098 




Microproof TRS-80 Model I or III 


$89.50 


TRS-80 Model III or 




CP/M 


$149.50 


Optional Correcting 




Feature 


$60 


Innovative Software Applications 




260 Sheridan, Suite 300 




Palo Alto, CA 94306 




(415) 326-0805 




Spellguard 2.0 


$295 


Micropro International Corp. 




1299 Fourth Street 




San Rafael, CA 94901 




(415) 457-8990 




Wordstar 3.0 


$495 


Microsoft 




400 108th Avenue NE, Suite 200 




Bellevue, WA 98004 




(206) 828-8080 




muSimp/muMath CP/M and Apple 


$250 


BASCOM BASIC 




Compiler CP/M and Apple 


$395 


Osborne Computer Corp. 




26500 Corporate Avenue 




Hayward, CA 94545 




(415) 887-8080 




Osborne 1 portable computer 


$1795 


Workman & Associates 




112 Marion Avenue 




Pasadena, CA 91106 




PDATA Minimum Data Base 


(postpaid) 




$84.50 



230 April 1982 © BYTE Publications Inc 



One Concept 1000 Supports 
16 CP/M User Stations 




■xpandable,Multi-Processor, Multi-User, 
Multi-Tasking Microcomputer System 

Here's computer power from Columbia Data Products that grows 
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works with a fully-dedicated Z-80A, 64K microprocessor s ystem with 
dual RS-232 or RS-422 serial ports in a complete CP/M® 'environ- 
ment Multi-processing is managed by Digital Research's MP/M® 
and CP/NET operating systems. You can start with the Concept 
1 000 . . . and stay with it. It grows with you. Contact us for more 
information on our newest Concept— the 1000. 



COLUMBIA 



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Home Office: West Cost: Europe: 

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Telephone 301-992-3400 Newport Beach. CA 92660 West Germany 

TWX 710-862-1891 Telephone 714-752-5245 Telephone 021-61-33159 

Telex 692 3 1 Telex 852 452 

Circle 91 on inquiry card. 



TIME MANAGER 



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HAYDEN 



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APPLESOFT COMPILER. 145.00 



MICROSOFT 

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BASIC COMPILER 315.00 

TASCAPPLES0F1® 

COMPILER 150.00 

FORTRAN 80 '. 165.00 

COBOL 80 550.00 

ALDS 105.00 

ADVENTURE 24.95 

OL YMPIC DEC A THALON 21.95 



Microhouse continues to feature 
the best savings on the best software. 



TERMINALS 

TELEVIDEO 



950 CALL 

925 CALL 

920 CALL 

912 CALL 

910 CALL 

PRINTERS 

C.ITOH 

PRO/WRITER SERIAL ...650.00 
PRO/WRITER PARALLEL 535.00 
STARWRITER I SERIAL .... CALL 
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dBASEII 

Version 2.0 599.00 



VIDEX 

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KEYBOARD ENHANCER. 105.00 

MICROSOFT 

Z-80 SOFTCARD 299.00 

16KRAMCARD 150.00 



VISICORP 

VISICALCi CALL 

VISIDEX-f 159.00 

VISIFILEi 200.00 

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SUPERSOFT 

TERM II 131.00 

DIAGNOSTICS II 84.00 

DISK DOCTOR 84.00 

FORTRAN 218.00 

SSS FORTRAN 

withRATFOR 285.00 

TINY PASCAL 74.00 



OKIDATA 



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AUTO-CAT 213.00 

D-CAT 156.00 



MICROSOFT 

BASIC 80 285.00 

BASIC COMPILER 315.00 

COBOL 80 568.00 

FORTRAN 80 345.00 

muSIMP-muMATH 215.00 

MACRO 80 140.00 

MICROPRO 

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SUPERSORT* 170.00 

MAILMERGE* 105.00 

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The Microhouse Order Center is Open from 9:00 AM 
until 8:00 PM Eastern Time Monday through Friday. 

Visa and MasterCard Welcome. 



FORORDERS-PRICEQUOTES' AVAIL ABILITY 

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' Trademarks of MicroPro International. 
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VISICORP IN PENNSYLVANIA 

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The Microcomputer People from Microhouse introduce 
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Microline is a computerized order-entry system, similar 
to accessing time-sharing systems. Microline is easy to 

use. All you need is a computer, a modem, a phone, and 

to follow these easy steps: 



PREMIUM 
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16K RAMCARD 
□ Z-80SOFTCARD 
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by TomHogan 

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619.00 



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4 Connect your modem to your phone. 

5 Hit the 'RETURN' key on your computer. A self-explanatory 
sign-on message will appear on your screen. 
Q Follow the instructions to shop and order through Microline . 
7 Payments by check, money order, C.O.D., MasterCard, or 
Visa only. 




The Microcomputer People. Microhouse 



Circle 272 on inquiry card. 



Circle 442 on inquiry card. 




System 2 

System 2 includes: 

• 68000 processor at 8MHz 

• 32 bit registers, operations 

• 7 vectored interrupt levels 

• 256KB parity checking RAM 

• 10MB Winchester hard disk 

• 960KB floppy disk 

• Graphics display monitor 

• Multibus™/IEEE architecture 

• XVX multiuser operating system 

• Option: UNIX™. CP/M™ 

• Screen editor, filer, linker 

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• Option: add 10MB Winchester 
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IMMEDIATE ATTENTION! 
Please send specifications on: 

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D System 2 ($8,500) 

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Name 

Company 

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Zip Phone 



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(319)344-0550 



Cable: 
XAVAXCORP 



XAVAX Corporation 

300 Northwest Tower 
Bettendort. Iowa 52722 



B482 



User's Column. 



How long has this been going on?" 

I shrugged. 

"You mean I went through three 
semesters of calculus and did ALL 
THOSE PROBLEMS while you had a 
computer program that would do dif- 
ferentiation and integrals? And I 
mashed through Physics I and II and 
solved problems with a hand calcu- 
lator when all that time Ezekial could 
have done my homework?" By now 
she was screaming. 

"Uh, well — " Under the circum- 
stances I did the only sensible thing a 
man could do. I hid behind my wife. 

But my lovely friend did have a 
point. True, muSimp/muMath are 
limited in what they can do, but they 
can do differentiation, integrals, and 
algebra. They can factor and expand 
polynomials. They can do matrix op- 
erations and simplify equations, and 
do it all symbolically, the way you'd 
mess around with the equations using 
pencil and paper. 

The programs aren't perfect. They 
tend to run out of memory easily. The 
way to escape that is to set up a kind 
of subprogram consisting of those ele- 
ments of muSimp/muMath that you 
need for your particular problem, 
leaving out all the parts that won't af- 
fect what you're doing. For example, 
you can configure a system that 
understands trigonometry and com- 
plex numbers but doesn't know that 
matrices and integrals exist. And so 
forth. 

There are other limits. The docu- 
mentation isn't exactly encrypted, but 
it's pretty dense. You really have to 
want to use the programs to dig your 
way through that stuff, and as I said 
earlier, it would help a lot if you 
understood LISP. The authors of the 
muSimp documents plainly do under- 
stand LISP, and although they don't 
expect you to, they keep hoping you 
will. 

Still in all, there's no real competi- 
tion for muSimp/muMath. If you 
want to do symbolic algebra, if you 
want to use your computer to help 
you get through Calculus 102 and 
Physics 203, then you probably need 
muSimp/muMath. 



Recommended for those who need 
it, with reservations as noted. 

BASCOM Improves 

More good news. Microsoft has 
done it again. It has improved its 
BASCOM BASIC Compiler. 

What Microsoft has done is two- 
fold: it's added program CHAINing 
with COMMON storage, meaning 
that you can break a program apart 
into pieces and execute it in parts, 
passing variables to each chunk as 
called. This greatly reduces the size of 
the program code that must be in 
memory at a given time, which means 
that it saves free memory and that you 
can run bigger programs with more 
variables. 

Second, Microsoft has greatly cut 
down on the run-time package, so the 
total size of the programs is — or can 
be — smaller, and also larger programs 
can be compiled and linked. 

More good news. Microsoft has 
partially dropped the restrictive licens- 
ing provision that made you pay a 
royalty on any program you sold that 
had been compiled with BASCOM. 

The bad news on that front is that it 
has dropped the royalty requirement 
only for the old BASCOM; if you 
want to use the new, with the CHAIN 
and COMMON keywords and smaller 
run-time package and all that nifty 
stuff, you still have to pay for each 
copy you sell. Alas. But I suspect free 
enterprise will end that; it's only a 
matter of time. 

Meanwhile, the new BASCOM is 
very nice indeed. Take a trivial exam- 
ple: an old Star Trek game I've been 
playing with. As you might suspect, 
my Star Trek is the ultimate game, 
with invisible Romulans, and shields 
for the Klingons, and enemy bases, 
and attacks on Federation bases, and 
Federation trading ships, and black 
holes, and — well, you get the idea. 

The game was originally written in 
EBASIC, a public-domain precursor to 
Gordon Eubanks' CBASIC. I added to 
it and translated it into CBASIC, but 
eventually the program outgrew that. 
Besides, it was getting awfully slow. 
What I wanted to do, therefore, was 



234 April 1982 © BYTE Publications Inc 




CP/M 



® 



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User's Column. 



translate it into Microsoft BASIC and 
compile it; but I couldn't because the 
program was just too large. I could 
break it into pieces for the Microsoft 
interpreter, but that was even slower 
than CBASIC. 

Comes new BASCOM and I've 
done it. Now I have a setup program 
which invents the game universe and 
makes the maps; then it calls in 
another program which processes 
commands; and every now and then 
still another program comes in and 
massages the data. It all works, letting 
me have a Star Trek so complicated 
that even I am beginning to think it's 
finished. 

Anyway, that's how the new com- 
piler works. On a more serious note, it 
will compile my tiny database. 

And here I have a problem. Should I 
review software that I have written? 
Certainly I have an obligation to tell 
you it's mine. I try to be objective, but 
certainly I could overlook flaws in my 
own programs. 

Minimum Data Base 

Minimum Data Base grew like 
Topsy. It started a long time ago with 
a thing called the People's Data Base 
by Yogesh Gupta and others. It was, 
in fact, the very first program I ever 
got running. When I bought Zeke, 
Mac Lean and Tony Pietsch handed 
me Debbie (a Microsoft-like BASIC 
that came with the Icom disk drives 
and, ugh, FDOS operating system); 
and they handed me a listing of the 
People's Data Base. 

"Get that running," they ordered. 

So I tried. Lord I tried. And I cer- 
tainly learned that semicolons are not 
colons, that single quote marks are not 
double quotes, that BASIC has a very 
precise syntax and improvements are 
not tolerated, and that I needed to 
keep my temper well enough so as not 
to throw anything heavy at Ezekial. 

Eventually I got it running. It wasn't 
a bad little program; more to the 
point, it was well structured, with a 
main routine and a series of subrou- 
tines, some of which themselves called 
other subroutines. There were no 
GOTO statements except within sub- 



236 April 1982 © BYTE Publications Inc 



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User's Column. 



routines. None of this grasshopper 
jumping about that so ruins BASIC'S 
reputation. 

The program was limited, and soon 
I ran into the limits. So I began to im- 
prove it. The sort algorithm used was 
a bubble sort. That wouldn't do, so I 
put in a Shell-sort algorithm. There 
were no disk operations. I fixed that. 
The command menu was processed in- 
efficiently, so I rewrote that and 
renamed most of the commands. The 
"delete entry" system was asinine, and 
I set up an entirely new way to handle 
that. And so forth. 

Year after year the silly thing 
grew — and I found I was using it for 
everything. It keeps phone numbers 
and addresses. It keeps the list of mem- 
bers of the Space Council and the L-5 
Board. When the Boy Scouts go hik- 
ing, a PDATA (after the original Peo- 
ple's Data Base) lets me make lists by 
meal (what are we eating for Thursday 
dinner?), or by who is carrying what 
(who's got Friday's lunch?), and all 
that. When I do an anthology, a 
PDATA file keeps track of who has 
how many shares and what they've 
been paid. When new royalties come 
in, it calculates what the new payment 
is and then writes the cover letter, 
makes mailing labels, and writes the 
checks. 

Versatile. And darned easy to use. 

"You ought to sell it," said Barry 
Workman of Workman Associates. 
"Let me handle it for you. It won't 
make you rich, but what do you care? 
People out there need the program." 

"Maybe," said I. "What if — gulp — 
what if someone reviews it and doesn't 
like the documentation? I can stand 
not being thought an elegant program- 
mer, but — " 

"Don't worry about it. I learned to 
use it, didn't I?" 

I shrugged. "Also, look, there's very 
little new in there. True, I didn't steal 
it from Gupta and the People's Data 
Base; there probably aren't ten lines of 
code left from their original. But it's all 
very straightforward code. Nothing 
elegant at all." 

"That's the value," Workman said. 
"Look, lots of people want a general- 
purpose do-all program, which is what 



this is. I notice that when you did all 
that statistical analysis, you used your 
PDATA thing." 

"Yeah." 

"And your Christmas cards are on 
it, and you used to keep your check- 
book balance — " 

"I don't do that any more. I use a 
Journal now." 

'Yeah, but you used to," Barry said. 

Eventually he wore me down. So. I 
mention PDATA, a small database 
and do-all, available from Workman 
Associates. If I didn't already have it, 
I'd probably buy it; I can't conceive of 
living without it, and I wouldn't have 
time to write it again. 

It is useful. And it's in both CBASIC 
and Microsoft BASIC, with the Micro- 
soft version compilable by BAS- 
COM— except that BASCOM will not 
compile the general program because 
it won't compile anything with arrays 
defined by variables. PDATA creates 
databases and dimensions them ac- 
cording to the number of fields you've 
specified, but BASCOM wants to 
know those dimensions in advance. 
This means that you can compile 
FONES (the telephone program) or 
NAND (name and address) or any set 
whose structure you know in advance, 
but you can't just compile PDATA. 

On the other hand, one reason 
PDATA is so useful is that you can 
run it interactively in interpreted 
Microsoft BASIC and write your own 
special-purpose routines (such as the 
one that determines what my contri- 
butors ought to be paid, given the 
total royalty). If you know BASIC at 
all, you can do a lot with PDATA. 

So. Useful, yes. But it is not a rival 
to dBase II and doesn't claim to be. All 
it claims to be is a very useful little 
general-purpose data handler that pro- 
vides a structure to let you mash data. 
And it will do all the statistics taught 
in elementary stat courses: sums, 
averages, standard deviations, me- 
dians, means, and correlations be- 
tween two variables. 

I've always liked it, and I'm happy 
to share it. 

Next time, more on Zeke's new 
friends and a lot more on financial 
programs. ■ 



238 April 1982 © BYTE Publications Inc 



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Book Reviews 



Handbook off 
Digital IC 
Applications 

by David L. Heiserman 
Prentice-Hall Inc. 
Englewood Cliffs, NJ 
1980, 428 pages, $21.95 



Reviewed by 

Clifford R. Mosley 

Network Test 

and Training Facility 

Building 25. Code 850.2 

Goddard Space Flight Center 

Greenbelt, MD 2077 1 



Ordering a book without 
first reading the fine print is a 



risky thing to do. I have 
found that getting what you 
order is not always the same 
as getting what you want. 
When I first saw the title of 
this book, I thought, natural- 
ly enough, 'This is a book 
full of digital IC application 
projects." Because I'm always 
anxious to build new gadgets, 
I promptly ordered the book. 
When it arrived, I tore open 
the package, flipped open the 
book, and found myself 
totally let down! It was not a 
collection of projects, but a 
book about basic digital con- 
cepts and devices. 

But I had paid good money 
for the book, and the least I 
could do was give it a closer 



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look. When I overcame my 
initial prejudice, I discovered 
that it did, in fact, have some 
very good characteristics. 

Handbook of Digital IC 
Applications appears to have 
been primarily designed as 
a textbook for a technical 
school or intermediate engi- 
neering course in digital de- 
sign. At the end of each seg- 
ment, Heiserman has in- 
cluded an exercise on key 
points to encourage further 
study. Answers to selected 
exercises are included in the 
back of the book, allowing 
readers to check the accuracy 
of their quiz answers. Despite 
the fact that the book is 
targeted for a technical au- 
dience, I feel that a serious 
hobbyist with a fair math 
background could learn a 
great deal. The text is sup- 
ported by many helpful il- 
lustrations and is written in a 
pleasantly explicit style. 

Basic combinational logic 
(AND, OR, INVERT, etc.) 
and Boolean algebra are the 
dominant subjects of the be- 
ginning chapters of the book. 
These fundamentals are dis- 
cussed in a little greater detail 
than in most books of this 
type. Heiserman then moves 
into a discussion of digital 
hardware, detailing the de- 
sign aspects of interfacing 
TTL (transistor-transistor 
logic) and CMOS (comple- 
mentary metal-oxide semi- 
conductor) logic with some 
of the more common input 
and output devices. He also 
discusses some of the prob- 
lems encountered when com- 
bining TTL and CMOS logic 
within the same system and 
describes flip-flops, counters, 
timers, code converters, dis- 
play drivers, AOI (AND-OR- 
INVERT) circuits, and other 
similar digital devices. 

In the final chapters, 
Heiserman introduces more 



complex devices such as data 
selectors, data multiplexers/ 
demultiplexers, parity gene- 
rators/detectors, arithmetic 
circuits, and memory cir- 
cuits. 

One of the greatest 
strengths of the book is 
Chapter 11, where Heiserman 
uses a refreshing approach to 
present an application of the 
basic theory of the earlier 
chapters. He leads the reader 
through the design of a sim- 
ple digital measuring system 
(in this case a frequency 
counter), developing each 
unit of the system as a sepa- 
rate block, then illustrating 
the process of integrating all 
of the blocks into a complete 
system. 

The book has some weak 
points. It lacks a glossary, 
and the index is a little skim- 
py. Both are important in a 
technical book in order to 
quickly locate information. 
These faults reduce the over- 
all effectiveness of the book 
as a learning aid. 

Also, some minor technical 
(or possibly editing) errors 
tend to confuse the reader. 
One example can be found in 
the first chapter, where the 
typical power consumption 
of a CMOS gate is listed at 
10 ns (nanoseconds). As it is 
standard practice to measure 
power consumption in units 
of watts, I assume that 
Heiserman intended the text 
to read 10 nw (nanowatts). 

Conclusion 

Handbook of Digital IC 
Applications is well written 
and superbly illustrated and 
would make an adequate 
digital-design textbook or 
tutorial for a serious hobby- 
ist. Although it wasn't the 
book I thought I had ordered, 
I am nevertheless pleased to 
have it as a part of my refer- 
ence library. ■ 



240 April 1982 © BYTE Publications Inc 



1982 NATIONAL 
COMPUTER CONFERENCE 

JUNE 7-10 • ASTRODOMAIN . HOUSTON, TEXAS 




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Designing the Star User Interface 

The Star user interface adheres rigorously to a small set of 

principles designed to make the system seem friendly by 

simplifying the human-machine interface. 



In April 1981, Xerox announced 
the 8010 Star Information System, a 
new personal computer designed for 
offices. Consisting of a processor, a 
large display, a keyboard, and a 
cursor-control device (see photo 1), it 
is intended for business professionals 
who handle information. 

Star is a multifunction system com- 
bining document creation, data pro- 
cessing, and electronic filing, mailing, 
and printing. Document creation in- 
cludes text editing and formatting, 
graphics editing, mathematical for- 
mula editing, and page layout. Data 
processing deals with homogeneous, 
relational databases that can be 
sorted, filtered, and formatted under 
user control. Filing is an example of a 
network service utilizing the Ethernet 
local-area network (see references 9 
and 13). Files may be stored on a 
work station's disk, on a file server on 

About the Authors 

These five Xerox employees have worked on 
the Star user interface project for the past five 
years. Their academic backgrounds are in com- 
puter science and psychology. 



Dr. David Canfield Smith, Charles Irby, 

Ralph Kimball, and Bill Verplank 

Xerox Corporation 

3333 Coyote Hill Rd. 

Palo Alto, C A 94304 

Eric Harslem 

Xerox Corporation 

El Segundo, CA 90245 

the work station's network, or on a 
file server on a different network. 
Mailing permits users of work sta- 
tions to communicate with one 
another. Printing utilizes laser-driven 
raster printers capable of printing 
both text and graphics. 

As Jonathan Seybold has written, 
"This is a very different product: Dif- 
ferent because it truly bridges word 
processing and typesetting functions; 
different because it has a broader 
range of capabilities than anything 
which has preceded it; and different 
because it introduces to the commer- 
cial market radically new concepts in 
human engineering." (See reference 
15.) 

The Star user interface adheres 
rigorously to a small set of design 
principles. These principles make the 
system seem familiar and friendly, 
simplify the human-machine interac- 
tion, unify the nearly two dozen func- 
tional areas of Star, and allow user 
experience in one area to apply in 
others. In reference 17, we presented 
an overview of the features in Star. 
Here, we describe the principles 



behind those features and illustrate 
the principles with examples. This 
discussion is addressed to the 
designers of other computer pro- 
grams and systems — large and small. 

Star Architecture 

Before describing Star's user inter- 
face, several essential aspects of the 
Star architecture should be pointed 
out. Without these elements, it would 
have been impossible to design an 
interface anything like the present 
one. 

The Star hardware was modeled 
after the experimental Xerox Alto 
computer (see reference 19). Like 
Alto, Star consists of a Xerox- 
developed, high-bandwidth, MSI 
(medium-scale integration) processor; 
local disk storage; a bit-mapped 
display screen having a 72-dots-per- 
inch resolution; a pointing device 
called the "mouse"; and a connection 
to the Ethernet network. Stars are 
higher-performance machines than 
Altos, being about three times as fast, 
having 512K bytes of main memory 
(versus 256K bytes on most Altos), 10 



242 April 1982 © BYTE Publications Inc 



Price 

Performance 

Reliability 




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Ethernets to one another either direct- 
ly or over telephone lines, enabling 
internetwork communication. (For a 
detailed description of the Xerox Alto 
computer, see the September 1981 
BYTE article "The Xerox Alto Com- 
puter" by Thomas A. Wadlow on 
page 58.) 

The most important ingredient of 



the user interface is the bit-mapped 
display screen. Both Star and Alto 
devote a portion of main memory to 
the screen: 100K bytes in Star, 50K 
bytes (usually) in Alto. Every screen 
dot can be individually turned on or 
off by setting or resetting the cor- 
responding bit in memory. It should 
be obvious that this gives both com- 
puters an excellent ability to portray 
visual images. We believe that all im- 
pressive office systems of the future 
will have bit-mapped displays. 
Memory cost will soon be insignifi- 
cant enough that they will be feasible 
even in home computers. Visual com- 
munication is effective, and it can't be 
exploited without graphics flexibility. 



244 April 1982 © BYTE Publications Inc 



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There must be a way to change 
dots on the screen quickly. Star has a 
high memory bandwidth, about 90 
megahertz (MHz). The entire Star 
screen is repainted from memory 39 
times per second, about a 50-MHz 
data rate between memory and the 
screen. This would swamp most com- 
puter memories. However, since 
Star's memory is double-ported, 
refreshing the display does not ap- 
preciably slow down processor 
memory access. Star also has separate 
logic devoted solely to refreshing the 
display. Finally, special microcode 
has been written to assist in changing 
the contents of memory quickly, per- 
mitting a variety of screen processing 
that would not otherwise be practical 
(see reference 8). 

People need a way to quickly point 
to items on the screen. Cursor step 
keys are too slow; nor are they 
suitable for graphics. Both Star and 
Alto use a pointing device called the 
mouse (see photo 2). First developed 
at Stanford Research Institute (see 
reference 6), Xerox's version has a 
ball on the bottom that turns as the 
mouse slides over a flat surface such 
as a table. Electronics sense the ball 
rotation and guide a cursor on the 
screen in corresponding motions. The 
mouse possesses several important 
attributes: 

• It is a "Fitts's law" device. That is, 
after some practice you can point 
with a mouse as quickly and easily as 
you can with the tip of your finger. 
The limitations on pointing speed are 
those inherent in the human nervous 
system (see references 3 and 7). 

• It stays where it was left when you 
are not touching it. It doesn't have to 
be picked up like a light pen or stylus. 

• It has buttons on top that can be 
sensed under program control. The 
buttons let you point to and interact 
with objects on the screen in a variety 
of ways. 

Every Star and Alto has its own 
hard disk for local storage of pro- 
grams and data. This enhances their 
personal nature, providing consistent 
access to information regardless of 
how many other machines are on the 



network or what anyone else is do- 
ing. Larger programs can be written, 
using the disk for swapping. 

The Ethernet lets both Stars and 
Altos have a distributed architecture. 
Each machine is connected to an 
Ethernet. Other machines on the 
Ethernet are dedicated as 
"servers" — machines that are at- 
tached to a resource and provide ac- 
cess to that resource. 

Star Design Methodology 

We have learned from Star the im- 
portance of formulating the fun- 
damental concepts (the user's concep- 
tual model) before software is writ- 
ten, rather than tacking on a user in- 
terface afterward. Xerox devoted 
about thirty work-years to the design 
of the Star user interface. It was 
designed before the functionality of 
the system was fully decided. It was 
even designed before the computer 
hardware was built. We worked for 
two years before we wrote a single 
line of actual product software. 
Jonathan Seybold put it this way, 
"Most system design efforts start with 
hardware specifications, follow this 
with a set of functional specifications 
for the software, then try to figure 
out a logical user interface and com- 
mand structure. The Star project 
started the other way around: the 
paramount concern was to define a 
conceptual model of how the user 
would relate to the system. Hardware 
and software followed from this." 
(See reference 15.) 

In fact, before we even began 
designing the model, we developed a 
methodology by which we would do 
the design. Our methodology report 
(see reference 10) stated: 

One of the most troublesome and 
least understood aspects of interactive 
systems is the user interface. In the 
design of user interfaces, we are con- 
cerned with several issues: the provi- 
sion of languages by which users can 
express their commands to the com- 
puter; the design of display representa- 
tions that show the state of the system 
to the user; and other more abstract 
issues that affect the user's understand- 
ing of the system's behavior. Many of 
these issues are highly subjective and 
are therefore often addressed in an ad 
hoc fashion. We believe, however, 



246 April 1982 © BYTE Publications Inc 



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that more rigorous approaches to user 
interface design can be developed. . . . 

These design methodologies are all 
unsatisfactory for the same basic 
reason: they all omit an essential step 
that must precede the design of any 
successful user interface, namely task 
analysis. By this we mean the analysis 
of the task performed by the user, or 
users, prior to introducing the pro- 
posed computer system. Task analysis 
involves establishing who the users 
are, what their goals are in performing 
the task, what information they use in 
performing it, what information they 
generate, and what methods they 
employ. The descriptions of input and 
output information should include an 
analysis of the various objects, or in- 
dividual types of information entity, 
employed by the user. . . . 

The purpose of task analysis is to 
simplify the remaining stages in user 
interface design. The current task 
description, with its breakdown of the 
information objects and methods 
presently employed, offers a starting 
point for the definition of a corre- 
sponding set of objects and methods to 
be provided by the computer system. 



The idea behind this phase of design is 
to build up a new task environment for 
the user, in which he can work to ac- 
complish the same goals as before, sur- 
rounded now by a different set of ob- 
jects, and employing new methods. 

Prototyping is another crucial ele- 
ment of the design process. System 
designers should be prepared to im- 
plement the new or difficult concepts 
and then to throw away that code 
when doing the actual implementa- 
tion. As Frederick Brooks says, the 
question "is not whether to build a 
pilot system and throw it away. You 
will do that. The only question is 
whether to plan in advance to build a 
throwaway, or to promise to deliver 
the throwaway to customers. . . . 
Hence plan to throw one away; you 
will, anyhow. " (See reference 2.) The 
Alto served as a valuable prototype 
for Star. Over a thousand Altos were 
eventually built. Alto users have had 
several thousand work-years of ex- 
perience with them over a period of 
eight years, making Alto perhaps the 



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largest prototyping effort ever. 
Dozens of experimental programs 
were written for the Alto by members 
of the Xerox Palo Alto Research 
Center. Without the creative ideas of 
the authors of those systems, Star in 
its present form would have been im- 
possible. In addition, we ourselves 
programmed various aspects of the 
Star design on Alto, but all of it was 
"throwaway" code. Alto, with its bit- 
mapped display screen, was powerful 
enough to implement and test our 
ideas on visual interaction. 

Some types of concepts are in- 
herently difficult for people to grasp. 
Without being too formal about it, 
our experience before and during the 
Star design led us to the following 
classification: 

Easy Hard 



concrete 


abstract 


visible 


invisible 


copying 


creating 


choosing 


filling in 


ecogmzing 


generating 


editing 


programming 


interactive 


batch 



The characteristics on the left were in- 
corporated into the Star user's con- 
ceptual model. The characteristics on 
the right we attempted to avoid. 

Principles Used 

The following main goals were pur- 
sued in designing the Star user inter- 
face: 

• familiar user's conceptual model 

• seeing and pointing versus remem- 
bering and typing 

• what you see is what you get 

• universal commands 

• consistency 

• simplicity 

• modeless interaction 

• user tailorability 

We will discuss each of these in turn. 

Familiar User's Conceptual Model 

A user's conceptual model is the set 
of concepts a person gradually ac- 
quires to explain the behavior of a 
system, whether it be a computer 



CALL TOLL FREE: (800) 854-2750; (800) 552-8817 in CA 



248 April 1982 © BYTE Publications Inc 



Circle 82 on Inquiry card. 




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system, a physical system, or a 
hypothetical system. It is the model 
developed in the mind of the user that 
enables that person to understand 
and interact with the system. The first 
task for a system designer is to decide 
what model is preferable for users of 
the system. This extremely important 
step is often neglected or done poor- 
ly. The Star designers devoted several 
work-years at the outset of the proj- 
ect discussing and evolving what we 
considered an appropriate model for 
an office information system: the 
metaphor of a physical office. 

The designer of a computer system 
can choose to pursue familiar 



analogies and metaphors or to in- 
troduce entirely new functions requir- 
ing new approaches. Each option has 
advantages and disadvantages. We 
decided to create electronic counter- 
parts to the physical objects in an of- 
fice: paper, folders, file cabinets, mail 
boxes, and so on — an electronic 
metaphor for the office. We hoped 
this would make the electronic 
"world" seem more familiar, less 
alien, and require less training. (Our 
initial experiences with users have 
confirmed this.) We further decided 
to make the electronic analogues be 
concrete objects. Documents would 
be more than file names on a disk; 



they would also be represented by 
pictures on the display screen. They 
would be selected by pointing to them 
with the mouse and clicking one of 
the buttons. Once selected, they 
would be moved, copied, or deleted 
by pushing the appropriate key. 
Moving a document became the elec- 
tronic equivalent of picking up a 
piece of paper and walking 
somewhere with it. To file a docu- 
ment, you would move it to a picture 
of a file drawer, just as you take a 
physical piece of paper to a physical 
file cabinet. 

The reason that the user's concep- 
tual model should be decided first 



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252 April 1982 © BYTE Publications Inc 



Circle 393 on inquiry card. 



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By Fred Huntington 

Time for our latest new program for the 
Apple \ Computer Almanac. Written by 
David Carman, an honest-to-goodness 
weatherman, Computer Almanac is a diverse 
collection of well thought-out programs. It 
contains sunrise and sunset times, weather 
forecasts for any year, a wind chill chart, light- 
ning safety rules, a super-duper extra easy to 
use loan amoritization program that will print 
out in 80 columns, health chapter (including a 
nifty calorie counter), a vacation planner, a 
biorythm chapter (needs printer) and more. 

We're very proud of this program and think 
that at $24.95, it's one of the best bargains 
in the software market today. Also, don't 
forget our other new program for the Apple \ 
Understand Yourself, also $24.95. Dealer 
inquiries welcome. 

Speaking of good programs, wed like to 
recommend for either home or school use 
Crossword Magic by L&S Computerware. A 
super outstanding program with nothing else 
even close, we thought the original price of 
$79.95 was a little steep. So we were able to 
convince them to lower it to $49.95, which is 
still a little steep for a crossword program, no 
matter how fantastic. So, to prove a point, 
we've set the price at $39.99. Now it's a 
bargain. 

It will work with most graphic printers, inc- 
luding the Epson, with or without the 
Grappler. 

GREAT GRANDMA HUNTINGTON 

Great Grandma Huntington told me when I 
was a lad that I should always buy my compu- 
ter media as a diskcount. She also said that a 
single density disk in the hand was better 
than a double density disk in the bush. 

Great Grandma Huntington said a lot of 
things, many of which I can't remember. So 
we're having a contest to see who can come 
up with the best Great Grandma Huntington 
sayings. All entries must be postmarked no 
lat ©than June 30, 1982 ad shou Icbe ad- 
dressed to: 

GREAT GRANDMA HUNTINGTON 

CONTEST 

P. O. Box 787 

Corcoran, CA 93212 

The top two entries will receive genuine 
Epson LC Digital Quartz watches (yep, made 
by the same people who make those great 
printers). Winners will be used in future Soft- 
lights columns. All entries become the prop- 
erty of Huntington Computing and will not be 
returned. The worst ones may be used in 
future advertising. 



Enhancer II (Videx) $131. 

Escape (Sublogic) $26.29 

Falcons (Piccadilly) $25.39 

Firebird (Gebelli) $23.39 

Fractions Concepts & Operations . $50.99 

Free Lance Software Marketing Kern (book) $24.44 

Game Paddles (TG) $33.89 

Goblins (Highland) $23.29 

GRAN PRIX (Riverbank) $25.39 

Hi-res Chemistry (J&S) $197.99 

Mastertype (Zwieg) $35.09 

Investment Decisions (Mesa Research) .... $84.99 
Maior League Baseball (Avalon Hill) ........ $25.49 

Micro Appte I (Micro Ink) $21.19 

Micro Apple II (Micro Ink) $21.19 

Micropamter (Datasoft) $31.99 

Micropamter Refill #1 (Datasoft) $16.89 

MicropamterRefill #2 (Datasoft) $16.89 

Monty PlaysMonopoly (Personal) $31 .99 

Monty Plays Scrabble (Personal) $33.89 

Mummy's Curse (Highland) $26.39 

Music System (Mountain) $349.00 

PFS (Software) $80.69 

PFS-Report (Software) $87.49 

Paddle-Adapple (So. Calif. Research) $26.89 

Physics I - Free Fall (Ed. Courseware) $28.09 

Pool 1 .5 (IDSI) $29.69 

Population (Ed. Courseware) $21.09 

Portfolio Master (Investors Software) $63.69 

Prisoner (Edu-Ware) $26.95 

Pro Football (SDL) $44.89 

Programmers Handbook (Comp. Sta.) $26.96 

Race for Midnight (Avant Card) $25.39 

Raster Blasier (Budge Co) $25.39 

Real Estate Analyzer (HowardsoM) $127.49 

Romwnter (Mountain) $148.69 

Sargon II (Hayden) $29.69 

Saturn Navigator (Sublogic) $21. 19 

Sentence Diagramming (Avant Gard) $21.19 

Sexoscope(AGS) $26.99 

Shuflleboard (IDSI) $25.39 

Star Thief (Cavalier) $25.39 

Suicide (Piccadilly) $26.29 

Super Sound (Rainbow) $14.39 

SuperCalc (Sorcim) : . . .$250.69 

Tablet Shape Maker (Rocky Mountain) $84.09 

Tanktics (Avalon Hill) $24.59 

Tax Preparer 82 (Howardsoft) $131.99 

Trickshot (IDSI) $35. f 

Using 6502 Assembly Lang, (bk) Datamost . $16, 

Valdez (Dynacomp) $ 16. 

Win At The Races (SDL) $44.89 

Wizardry (Sir Tech) $42.39 

Word Star (Micro Pro) $289.00 

Z Card (ALS) $239. OO 

Z-Term (Southwestern) 



Call TOH-Free 800-344-5106 (outside California) 



HUNTINGTON COMPUTING 



We take MasterCard, American Express or VISA (Include card # and 



Post Office Box 1297 
Corcoran, California 93212 



Apple- is a registered trademark of Apple Computer, inc. expiration date). California residents add 6% tax. Include S2.00 for postage. _. 

Pet- isa registered trademark of Commodore. Foreign and hardware extra. Foreign (excluding Canada): remit U.S. cur- W2 

rency, checks on U.S. banks, use listed charge cards, or make direct wire !m 

transfers through Security Pacific Bank, Corcoran, for a S6.00 charge. All « 

Outside Calif. 800-344-5106 overseas orders shipped by air. Send for free catalog. Prices subject to |JJ 



TRS-80 ' i s a registered trademark of Tandy Corp. 
Atari • is a registered trademark of Atari, Inc. 



Circle 197 on inquiry card. 



BYTE April 1982 253 



:■:•:•:•: 


1*1*1*1*1 * ^^^^S^^^^^^^i^^^^l I '!' 

■iiiiiiiiii::: out , OM:! 




1 


i;!; 


'i'i'i 1 .' 




lllfCji 

^X^xUl IN 






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j* 




mm^ m ir ,;, 


!:!:!:!:!:!:;: : :::;[C:'ave 




■!•!•!•£•:& 


:•:•;•:»:■:•:*:•:■:•;•;•:•: 









Figure 1: In-basket and out-basket icons. The in-basket contains an envelope indicating 
that mail has been received. (This figure was taken directly from the Star screen. 
Therefore, the text appears at screen resolution.) 



TtuieupjourLA36 



The DS120 Terminal Controller makes your LA36 
perform like a DECwriter® III. 

The Datasouth DS120 gives your DECwriter® II the high speed printing 
and versatile performance features of the DECwriter® III at only a frac- 
tion of the cost. The DS120 is a plug compatible replacement for your 
LA36 logic board which can be installed in minutes. Standard features 
include: 



• 165 cps bidirectional printing 

• Horizontal & Vertical Tabs 

• Page Length Selection 

• 110-4800 baud operation 

• 1000 character print buffer 

• X-on, X-off protocol 

• Self Test 



• RS232 interface 

• 20 mA Current Loop interface 
■ Top of Form 

• Adjustable Margins 

• Double wide characters 

• Parity selection 

• Optional APL character set 



Over 5,000 DS120 units are now being used by customers ranging from 
the Fortune 500 to personal computing enthusiasts. In numerous instal- 
lations, entire networks of terminals have been upgraded to take advan- 
tage of today's higher speed data 
communications services. LSI 
microprocessor electronics 
and strict quality control en- 
sure dependable performance 
for years to come. When ser- 
vice is required, we will 
respond promptly and effec- 
tively. Best of all, we can de- 
liver immediately through 
our nationwide network of 
distributors. Just give us a 
call for all the details. 




data 



computer corporation 



4740 Dwight Evans Road • Charlotte, North Carolina 28210 • 704/523-8500 



when designing a system is that the 
approach adopted changes the func- 
tionality of the system. An example is 
electronic mail. Most electronic-mail 
systems draw a distinction between 
messages and files to be sent to other 
people. Typically, one program sends 
messages and a different program 
handles file transfers, each with its 
own interface. But we observed that 
offices make no such distinction. 
Everything arrives through the mail, 
from one-page memos to books and 
reports, from intraoffice mail to inter- 
national mail. Therefore, this became 
part of Star's physical-office 
metaphor. Star users mail documents 
of any size, from one page to many 
pages. Messages are short documents, 
just as in the real world. User actions 
are the same whether the recipients 
are in the next office or in another 
country. 

A physical metaphor can simplify 
and clarify a system. In addition to 
eliminating the artificial distinctions 
of traditional computers, it can 
eliminate commands by taking ad- 
vantage of more general concepts. 
For example, since moving a docu- 
ment on the screen is the equivalent 
of picking up a piece of paper and 
walking somewhere with it, there is 
no "send mail" command. You sim- 
ply move it to a picture of an out- 
basket. Nor is there a "receive mail" 
command. New mail appears in the 
in-basket as it is received. When new 
mail is waiting, an envelope appears 
in the picture of the in-basket (see 
figure 1). This is a simple, familiar, 
nontechnical approach to computer 
mail. And it's easy once the physical- 
office metaphor is adopted! 

While we want an analogy with the 
physical world for familiarity, we 
don't want to limit ourselves to its 
capabilities. One of the raisons d'etre 
for Star is that physical objects do not 
provide people with enough power to 
manage the increasing complexity of 
the "information age." For example, 
we can take advantage of the com- 
puter's ability to search rapidly by 
providing a search function for its 
electronic file drawers, thus helping 
to solve the long-standing problem of 
lost files. 



254 April 1982 © BYTE Publications Inc 



Circle 139 on inquiry card. 




Amdek's Video-300 green phosphor monitor 
is the easy-reading choice for almost any 
system— including IBM and Apple. 



Everything about our 12" Video-300 
monitor was designed to be easy. Easy 
to read. Easy to use. And easy to match 
up with practically any computer or 
word processing system, including the 
popular Apple and IBM personal com- 
puters. So it's easy to see why you 
should choose Video-300 for your text 
display needs. 

Amdek's Video-300 monitor 
features: 

• Non-glare screen to eliminate dis- 
tracting reflections 

• P-31 green phosphor display for 
no-strain viewing 

• 80 x 24 character display 



• 18MHz band width 900 lines [center) 
resolution 

• Built-in carrying handle for porta- 
bility 

• Light-weight, industrial-grade cabine- 
try [only 17 lbs.] 

• UL, FCC approved 

• Full one-year warranty covering 
parts and labor 

So ask your dealer about Video-300 
— part of Amdek's complete line of 
color, green phosphor and black and 
white monitors, then match Video- 
300's performance and price against 
any other display monitor. For quality 
and value, you'll choose Amdek. 



Amdek Corporation, 2420 E. Oakton St., Suite E, Arlington Heights, IL 60005. (312] 364-1180 • TLX: 25-4786 



Circle 24 on inquiry card. 



BYTE April 1982 255 



The "Desktop" 

Every user's initial view of Star is 
the "Desktop/' which resembles the 
top of an office desk, together with 
surrounding furniture and equip- 
ment. It represents your working en- 
vironment — where your current proj- 
ects and accessible resources reside. 
On the screen are displayed pictures 
of familiar office objects, such as 
documents, folders, file drawers, in- 
baskets, and out-baskets. These ob- 
jects are displayed as small pictures or 
"icons," as shown in figure 2. 

You can "open" an icon to deal 
with what it represents. This enables 
you to read documents, inspect the 
contents of folders and file drawers, 
see what mail you have received, etc. 
When opened, an icon expands into a 



larger form called a "window," which 
displays the icon's contents. Win- 
dows are the principal mechanism for 
displaying and manipulating infor- 
mation. 

The Desktop "surface" is displayed 
as a distinctive gray pattern. This 
restful design makes the icons and 
windows on it stand out crisply, 
minimizing eyestrain. The surface is 
organized as an array of one-inch 
squares, 14 wide by 11 high. An icon 
can be placed in any square, giving a 
maximum of 154 icons. Star centers 
an icon in its square, making it easy 
to line up icons neatly. The Desktop 
always occupies the entire display 
screen; even when windows appear 
on the screen, the Desktop continues 
to exist "beneath" them. 



The Desktop is the principal Star 
technique for realizing the physical- 
office metaphor. The icons on it are 
visible, concrete embodiments of the 
corresponding physical objects. Star 
users are encouraged to think of the 
objects on the Desktop in physical 
terms. Therefore, you can move the 
icons around to arrange your 
Desktop as you wish. (Messy 
Desktops are certainly possible, just 
as in real life.) Two icons cannot oc- 
cupy the same space (a basic law of 
physics). Although moving a docu- 
ment to a Desktop resource such as a 
printer involves transferring the 
document icon to the same square as 
the printer icon, the printer im- 
mediately "absorbs" the document, 
queuing it for printing. You can leave 



lO-tarpirture 1 



mr^ F^n 



® 



XEROX STAR User-lnterfacet 



DOCUMENT OBJECTS 
Page 

Text 

charactei 
paragraph *'--.. 

Frame 

Graphic;... 
line '--.. 

symbol 
chart 
Table 

Equation 
Lr-r 

Field 
Footnote 





-iS 


111 


■ n .... 

■'.:□□■ 





UNr/ERSAL COMMANDS 

Delete 

■-*py 

Move ■ 

:. how Properties 

CcpyPropertle; 

undo 

Help 



Document 

Record File 
Polder' 

Pile Drawer 

in- and Out-Basl ets 

Printer 

Floppy C'L.l Drive 

'J jet' "and ij;er Group 

Calculator 

Terminal Emulator; 

Chert er 

Oifectory 



I MOUSE 



Select Adjust 



X 




EJE 








~k| 


Met 
Fori 


"" : ' 



^STTf 



Sale j 

report 


















Sale; 
Figure; 




February 

Sales 

Fieturei 





Figure 2: A Desktop as it appears on the Star screen. Several commonly used icons appear across the top of the screen, including 
documents to serve as "form-pad" sources for letters, memos, and blank paper. An open window displaying a document containing 
an illustration is also shown. 



256 April 1982 © BYTE Publications Inc 



The revolutionary Discovery multiprocessor is the only system that 
allows the total integration of powerful 16 bit 8086 processors with 
the more standard Z-80 user processors. The DISCOVERY system may 
be configured in any 8 bit/16 bit combination, or as a totally exclusive 
16 bit system only to provide the ultimate in performance and flexibility 
in advanced micro systems. 

Ultimate performance. The dpc-186 is the most sophisticated single 
board microcomputer available today offering more power and faster 
processing time through the 8086 CPU for bigger, more complex 
programs. Memory starts at 128 K (compared to the Z-80's 64 K), and 
is expandable to 1 megabyte. And the dpc-186 is fully compatible with 
the standard DISCOVERY multiprocessor system permitting efficient 
upgrading as future needs develop, without sacrificing any of your 
extensive hardware and software investment. 



World's best multiprocessor system. The DISCOVERY system pro- 
vides separate processors and memory for each of its 16 users. It offers 
full CP/IVrand CP/M-86 w compatibility, interprocessor communication, 
and shared and private files. Each user can take advantage of shared 
peripherals and cross submitting of tasks between processors.The system 
is controlled by a unique, two board dpc-280 service processor and 
dpc/os distributed processing operating system. 
By the board or by the system.The DISCOVERY multiprocessor is 
ready for immediate delivery as a complete system, as processor boards, 
and everything in between. It offers exclusive technology in multipro- 
cessing, yet is fully compatible with existing standards including CP/M 
and S-100. It is quite simply unmatched in performance, capabilities 
and offers a far greater degree of flexibility. 
DISCOVERY— offering a whole new world of possibilities. 



For the first time, 8 and 16 bit processor intermixing. 







Action Computer Enterprises, Inc. 



E23 



The Multiprocessing Company 

55 West Del Mar Boulevard, Pasadena. CA 91105 USA 

(213) 793-2440. TWX 910-588-1201 



Dealer and OEM inquiries invited. 

*CP/M is a registered TM of Digital Research, Inc. 



Circle 9 on inquiry card. 



We Were Here Yesterday... 
We Will Be Here Tomorrow 
With Support ft Service For You! 

SUPRBRAIN 

64k D/D 64k QD 

$ 2565 $ 2945 





NORTHSTAR 



HORIZON II 



LIST 
$4195 



64k QD $ 3275 



ADVANTAGES 125 



HARD DISKS 

5mb for IBM, Superbrain, S-100, 
Zenith, TRS-80 II & III, Xerox, 
Apple. 



$ 



2795 



CORVUS 

Call For Prices 



5Y4" DISK DRIVES 

TANDON S/S D/D ' • 

IBM COMPATIBLE *225 

TANDON D/S D/D $ 350 

TANDON 100-4 80 track... $ 600 

SUPERBRAIN ADD-ON 

S/S, 0/0 w/power supply, cable, case, 
software, one drive. 



$ 



365 



TERMINALS 

Many brands available. 
Call for prices. 



COMET II PRIMTER ^ $795 

EPSON MX80 parallel $479 

EPSON MX100 $740 

Cltoh F10 40 cps parallel * $1550 

NEC 7710, 7730 • $2395 

NEC 3510 rs232 • $1895 

DATA SOUTH 180 cps $1355 

OKIDATA 82A $530 

MPI88Gi20cps $550 

MPI 99G L.C. decenders $050 

• Tractors Available $220 



• 

DISKETTES 
DYSAN 

5V4" S/S, D/D 

'34.70 

BOX OF 10 
• 



SUPERBRAIN 

S-100 Bus Adapter 
LIST $595 



$ 475 



SUPERBRAIN 
Parallel Port 



SBE Prom 



LIST $90 

$ 75 

LIST $205 

s 155 



SOFTWARE 

C Basic II '98 

M Basic 80 *275 

MT Pascal '430 

Fortran 80 '450 

Cobol 80 WO 

M Basic Compiler. . .'329 

ACCT. Plus, '395 

Word Star '305 

Supercalc *2B5 

D-Base II '6D0 



GRAPHICS 

For SUPERBRAIN 

Graphics Board '896 

Symbol Generator. . .'200 

Graphics Plotter '200 

3-D Graphics '400 

Surface Plotter '460 

Graphics Terminal 
Emulator '450 



Toil-Free Ordering 1-800-426-2662 

For Information Calf(206) 453-8159 

Mail and telephone orders only. Mastercharge, VISA add 3%. C00 Certified check under 
$1000. All prices FOB origin. Send for catalog. Mail all correspondence to P.O. Box 3952, 
Bellevue, WA 98009 

PACIFIC COMPUTER BROKERS 

P.O. Box 3952, Bellevue, WA 98009 



documents on your Desktop in- 
definitely, just as on a real desk, or 
you can file them away in folders or 
file drawers. Our intention and hope 
is that users will intuit things to do 
with icons, and that those things will 
indeed be part of the system. This will 
happen if: 

(a) Star models the real world ac- 
curately enough. Its similarity with 
the office environment preserves your 
familiar way of working and your ex- 
isting concepts and knowledge. 

(b) Sufficient uniformity is in the 
system. Star's principles and 
"generic" commands (discussed 
below) are applied throughout the 
system, allowing lessons learned in 
one area to apply to others. 

The model of a physical office pro- 
vides a simple base from which learn- 
ing can proceed in an incremental 
fashion. You are not exposed to 
entirely new concepts all at once. 
Much of your existing knowledge is 
embedded in the base. 

In a functionally rich system, it is 
probably not possible to represent 
everything in terms of a single model. 
There may need to be more than one 
model. For example, Star's records- 
processing facility cannot use the 
physical-office model because 
physical offices have no "records pro- 
cessing" worthy of the name. 
Therefore, we invented a different 
model, a record file as a collection of 
fields. A record can be displayed as a 
row in a table or as f illed-in fields in a 
form. Querying is accomplished by 
filling in a blank example of a record 
with predicates describing the desired 
values, which is philosophically 
similar to Zloof's "Query-by- 
Example" (see reference 21). 

Of course, the number of different 
user models in a system must be kept 
to a minimum. And they should not 
overlap; a new model should be in- 
troduced only when an existing one 
does not cover the situation. 

Seeing and Pointing 

A well-designed system makes 
everything relevant to a task visible 
on the screen. It doesn't hide things 
under CODE + key combinations or 



258 April 1982 © BYTE Publications Inc 



Circle 318 on inquiry card. 



Systems II €x 



a total business system. 



JOB COSTING MENU 

1. TRANSACTION ENTRY/DATE 

2. JOB/TASK TABLE MAINTENANCE 

3. JOB COST FILE MAINTENANCE 

4. JOB COST REPORTING 

5. EMPLOYEE TABLE MAINTENANCE 

6. RETURN TO MASTER MENU 

SELECT (1-6)? 



SYSTEMS II EX 
MASTER MENU 
'1. INVENTORY 7.CHART0FACCTS. 

2. PAYABLES 8. VENDOR MA1NT. 

3. RECEIVABLES 9. CUST. MAINT. 

4. PAYROLL 10. CHANGE OATE 

5. LEDGER 11.SYS./BACKUP 

6. JOURNAL 12.ST0PPR0CSSG. 

13. OPTIONAL PROCSSG. 
L' SELECT (1-1 3|? 



DATABASE MENU 

1. FILE MAINTENANCE 

2. REPORTS/REPORT MAINT. 

3. UTILITIES 

4. RETURN TO SYSTEM MENU 

SELECT (14)? 



ACCOUNTS PAYABLES MENU 

1. FILE MAINTENANCE 

2. PAYMENT SELECTION 



RECEIVABLES SYSTEM MENU 

1. FILE MAINTENANCE 

2. RECEIPT OF PAYMENTS 

3. GENERATE BILLING 



SELECT (1-5)? 



6. APPLY MONTHLY INTEREST 

7. RETURN TO MASTER MENU 
SELECT (1-7)? 




LEDGER SYSTEM MENU 

1. FILE MAINTENANCE 

2. BAL SHEET/INCOME STATEMENT 

3. YEAR END PROCESS 

4. RETURN TO MASTER MENU 

SELECT (14)? 



SYSTEMS II EX — EX for EXTENDED 
PERFORMANCE. Westware brings you the 
most completely integrated and simplest to 
use business software for your Apple 
Computer. The SYSTEMS II EX is complete 
with an integrated Database. Yes! The DBII 
Database can move your system's files into 
Database format for customized reports or 
labels. 

Although the SYSTEMS II EX is a fully 
integrated system, you may purchase 



INVENTORY SYSTEM MENU 
TIME DATE 

1. FILE MAINTENANCE 

2. POINT OF SALES 

3. REORDER REPORT 



SELECT (14)? 



STATE 
PAYROLL MENU 

1. MISC/TAX TABLE MAINT. 

2. TRANSACTION FILE 

3. MISC. PAY/DEDUCTION FILE 

4. EMPLOYEE MASTER FILE 

5. CALCULATE/PRINT CHECKS 

6. PRINT WZs 

7. RETURN TO MASTER MENU 
SELECT (1-7|? 




individual modules and later add additional 
modules, such as Job Costing for 
contractors. The power of our system is in 
the KSAM Firmware card that plugs into the 
Apple. This card permits high speed 
searches and eliminates running sort 
routines to get your files in order. 

SYSTEMS II is available on 5 1 /»" drives, and 
also on the Corvus hard disk. A Corvus 
based system will give you the power and 
capacity that challenges larger computers. 



COMING SOON — Cash flow analysis with 
graphics, Database II with graphics, and Bill 
of Materials for small manufacturers. 

CURRENT OPTIONS AVAILABLE — Job 
Costing, Cycle Invoicing, Order entry, and 
Layaway. 

All Checks, statements and invoices use 
NEBS forms. 

Dealer and OEM inquiries invited. 

Apple is a trademark of Apple Computers. 



Systems II €x 

2455 S.W. 4th Ave. 
Suite 2 

Ontario, "OR 97914 
(503) 881-1477 
Circle 435 on inquiry card. 



Yes. please send 1 
me your Systems II 
i Demo Package. 




□ Yes, I would like to sample your software. Please 
send me the Systems II Demo Package. My check 
for $25 is enclosed. 

Name 



2455 S.W. 4th Ave. 
Suite 2 

Ontario, OR 97914 
1(503) 881-1477 



Title 



Company Name. 
Address 



City 



. State . 



Zip. 



force you to remember conventions. 
That burdens your memory. During 
conscious thought, the brain utilizes 
several levels of memory, the most 
important being the "short-term 
memory." Many studies have ana- 
lyzed the short-term memory and its 
role in thinking. Two conclusions 
stand out: (1) conscious thought deals 
with concepts in the short-term 
memory (see reference 1) and (2) 
the capacity of the short-term 
memory is limited (see reference 14). 
When everything being dealt with in 
a computer system is visible, the 
display screen relieves the load on the 



short-term memory by acting as a sort 
of "visual cache." Thinking becomes 
easier and more productive. A well- 
designed computer system can actual- 
ly improve the quality of your think- 
ing (see reference 16). In addition, 
visual communication is often more 
efficient than linear communication; 
a picture is worth a thousand words. 
A subtle thing happens when 
everything is visible: the display 
becomes reality. The user model 
becomes identical with what is on the 
screen. Objects can be understood 
purely in terms of their visible 
characteristics. Actions can be 



understood in terms of their effects on 
the screen. This lets users conduct ex- 
periments to test, verify, and expand 
their understanding — the essence of 
experimental science. 

In Star, we have tried to make the 
objects and actions in the system visi- 
ble. Everything to be dealt with and 
all commands and effects have a visi- 
ble representation on the display 
screen or on the keyboard. You never 
have to remember that, for example, 
CODE + Q does something in one 
context and something different in 
another context. In fact, our desire to 
eliminate this possibility led us to 



For The Best In Price, Selection and Delivery, 



Call Now TOLL FREE 

800-368-3404 

(In VA, Call Collect 703-327-8695) 

AMPEX-INTERTEC-TEXAS INSTRUMENTS- GENERAL DATA 

COMM. -ANDERSON JACOBSON-C. ITOH-QUME • BEEHIVE- 

DATAS0UTH-DIABLOCENTR0NICS • NEC • PRENTICE 



EpasEa 

INTERTEC: 

Superbrain QD $2995 

Bannsa 

DATASOUTH: $1235 

NEC: 

7710 $2196 

7715 Call for Special Price 

7730 $2196 

7720 Call for Special Price 

7725 Call for Special Price 

Std. Forms Tractor $ 200 

Bi-Dir. Forms Tractor $ 300 

CENTRONICS: 

739-1 (Parallel) $ 649 

739-3 (Serial) Call for Special Price 

QUME: 

Sprint 5, 55RO $2339 

Sprint 5, 55KSR Call 

Sprint 9, 45RO, 

Limited Panel $1845 

Full Panel $1969 

Std. Forms Tractor $ 1 99 

Bi-Dir. Forms Tractor $ 199 



DIABLO: 

630-R102RO $1995 



TERMINALS 



AMPEX: 

Dialogue 30 $ 775 

Dialogue 80 $ 939 

BEEHIVE: (SMART DISPLAY) 

DM5 $ 745 

DM5A $ 930 

DM310 (3101 Emulator) . . .$1095 
NOTE: IBM and Burroughs compatible ter- 
minals available. Please inquire. 
C. ITOH 

CIT 101 $1350 

TEXAS INSTRUMENTS: 

745 Standard $1390 

810 Basic $1249 

810 Package $1439 

820 Package RO Package .$1610 

820 RSR Package Call 

840 RO Basic $ 795 

840 RO Tractor Feed Pkg. .$1059 

K'l'IdMiHi 

STAR: 

300 Baud $ 149 




DISC DRIVES 



QUME: 

DataTrak5 .. .$325 or 2 for $599 
Data Trak 8 . . $549 or 2 for $1 049 



SOFTWARE 



769 
319 
215 
789 
179 



BISYNC-80RJE $ 

Wordstar $ 

Data Star $ 

Cobol $ 

Forms 2 (Cobol Gen.) $ 

Mail Merge $ 99 

Spell Guard $ 229 

Plan 80 $ 249 

Super Calc $ 249 

Milestone $ 249 

Most items are in stock now. In addi- 
tion, we can make EIA RS232 or 
RS449 cables to your order, and 
supply you with ribbons, printer 
stands, print wheels, thimbles for 
all printers listed. And many, many 
more items. CALL NOW. 

Add 2% for shipping and insurance. Superbrain 
shipped frsight collect. VISA and MasterCards 
welcomed; add 3% for credit card purchases. 
Virginia residents, add 4% Sales Tax. For fastest 
delivery, send certified check, money order or 
bank-wire transfer. Sorry, no C.O.D. orders. All 
equipment is in factory cartons with manufac- 
turers' warranty. Prices subject to change without 
notice. 



■ «■■*■ 



TCRftMBLS fiiiins 



Terminals Terrific, Incorporated, P.O. Box 490, Falls Church, VA 22046, 800-368-3404 (In VA, Call Collect 703-237-8695). 



260 April 1982 © BYTE Publications Inc 



Circle 412 on inquiry card. 





"We provide business 
programs as individual as 
your business needs. 5 ' 

"Allow me to introduce myself. I'm a Vector 
com puter, dedicated to the advancement of society. And 
I'd like to tell you how a computer can help you man- 
age your business more efficiently. Especially if that 
computer is a Vector, like me. Because we're prob- 
ably the most flexible and cost-effective computers you 
can find. 

"Our programs are the key. Because they enable 
me to handle sales forecasting, budgeting, job costing 
and proposals, commissions, personalized mass mail- 
ings, charts and graphs. We Vectors can even talk to each 
other and to other bigger computers. 

"Unique combinations of our individual pro- 
grams can actually customize me to meet your specific 
requirements. Any combination of our software pack- 
ages can be assembled right off the shelf, to help you 
realize your full potential as a salesman, merchant, 
stockbroker, clergyman, contractor, real estate or insur- 
ance agent or whatever your business. 

- "Choose from Memorite III for word processing 
and mail list management, Execuplanforfinancial plan- 
ning and forecasting, Business Accounting, Data 
Management for filing and sorting information, Com- 
munications and a host of others. And, of course, all we 
Vectors come with the popular CP/M operating system. 

"For more information and your local dealer, 
call us at (805)499-5831 or (800) 235-3547. In California, 
cal I (800) 322-3577. Or write to us at 500 North Ventu 
Park Road, Thousand Oaks, CA 91320. 

"We'll show you how we small information systems 
can mean big business for you'.' 

Circle 424 on inquiry card. 



Vector Graphic, Inc. 
COMPUTERS FOR THE ADVANCEMENT OF SOCIETY. 

Sold and supported by 400 dealers worldwide. 

Vector Productsare approved on General ServicesAdministration authorized ADP 

scheduled price list. 



Circle 278 on inquiry card. 



MAR. SPECIAL SALE ON PREPAID ORDERS 

(CHARGE CARDS. C.O.D. R P.O/S NOT AVAILABLE) 

MEM-4 INTRODUCTORY SALE 
65K STATIC RAM/ROM. OSES USES TMS 4016/TMM 
2016 RAM OR 2716 EPROMS EXTENDED ADDRESSING. 
AVAILABLE END OF APRIL 

PCBD $35.95. KIT LESS MEMORY $89.95 

A & T LESS MEMORY $1 29.95 



€ 



CALIFORNIA COMPUTER SYSTEMS 

S100 

2032 32K STATIC RAM A & T. 200 NSEC S629.00 

2065 64K DYNAMIC RAM A & T. . . $548.95 

2200 S-100 MAIN FRAM A&T $379.95 

2422 FLOPPY DISC WITH CP/M 2.2 ,u S329.95 

2810A Z80 CPU A & T S249.95 

2710A 4 SERIAL 1/0 A & T $291.95 

2718A 2 SERIAL, 2 PARALLEL A&T $305.95 

2720A 4 PARALLEL A&T S214.95 

PROTO BOARDS WW $39.95 

APPLE PRODUCTS 

7114A 1 2K ROM/PROM $68.50 

7424A CALENDAR/CLOCK. $106.95 

7440A PROGRAMMABLE TIMER $98 50 

7470A A TO CONVERTER , $105.95 

7490A GPIB (IE 488) INTERFACE $265.95 

7710A ASYNC SERIAL $1 25.95 

7712A SYNC SERIAL. .$153.95 

7720A PARALLEL STANDARD $98.95 

7720B PARALLEL CENTRONICS $98.95 

7811 B ARITHMETIC PROCESSOR W/DISC . . $342.95 
781 1C ARITHMETIC PROCESSOR W/ROM. ... $342.95 

7500A WW BOARD S22.95 

7510A SOLDERTAIL BOARD $23.95 



JS5S7 



MICROCOMPUTER PRODUCTS 



S100 PRODUCTS 
CB-2 280 PROCESSOR BOARD. 
KIT $198.95. A&T S269.95 

VBIC64 x 16 VIDEO. PCBD $32.95 

KIT $153 95, A&T $199 95 

VB3 80 CHARACTER VIDEO 4MHZ. 

KIT $345.95. A&T S425.95 

I04 2 PARALLEL, 2 SERIAL. PCBD $32.95 

KIT $155.95. A&T ... 



PB-1 2708, 2716 PROGRAMMER BOARD. 
KIT $135.95. A&T 



S194.95 
. S185.95 



APPLE PRODUCTS 

AIO SERIAL/PARALLEL INTERFACE 

KIT S125.95. A&T.. S155.95 

ASIO SERIAL I/O 

KIT S87.95. A&T S97.95 

APIO PARALLEL IO W/O CABLES 

KIT... $67.95 A&T $87.95 



v/mCj 



If?C. WAMECO INC. 



BOARDS WITH MIKOS PARTS 

MEM-3 32K STATIC RAM, PCBD $36.95 

KIT LESS RAM $95.95, A&T $135.95 

CPU-2 Z80 PROCESSOR. PCBD $32.95 

KIT LESS ROM S1 09 95. A&T $149.95 

EPM-2 16K/32K EPROM, PCBD $32.95 

KIT LESS ROM S65.95. A&T S99.95 

FPB-1 FRONT PANEL. PCBD S48.50 

KIT $144.95, A&T $184.95 

QMB-12 13 SLOT MOTHER BOARD. PCBD $39.95 

KIT $95.95, A&T ,...$135.95 




MONDAY-FRIDAY, 8:00 TO 1 2:00. 1 :00 TO 5:30 
THURSDAYS, 6:00 TO 9:00 P.M. 
(415) 728-9121 
P.O. B0X955 • ELGRANADA, CA94018 

PLEASE SEND FOR IC. XISTOR AND COMPUTER PARTS LiSl 
VISA or MASTERCHARGE. Send account number, interbank number. 
expiration date and sign your order. Approx. postage will be added 
Orders with check or money order will be sent post paid in US If you are 
not a regular customer, please use charge, cashier's check or postal 
money order. Otherwise there will be a' two-week delay lor checks to 
clear Calif, residents add 6% tax Money back 30-day guarantee We 
cannot accept returned IC's that have been soldered to Prices subject to 
change without notice $20.00 minimum order. 12.00 service charge on 
orders less thin S20.00. 



M ,t. U . U ^A / l l l |l l ,' „ l ll l l , U l .l ll U ;,A^ X A * A*AAA,l.MAA.i. ,. ,1 1 . . 1 . . 1 , ,j, . 1 . .1. . 1 i„l ,i,, W U .I.. W .. 



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IHARACTER PROPERTIES 



Durie|Defdult; 



Display 



CHARACTER 



PARAGRAPH T A B SETTING: 



Font [Class! 



\msm 



Titan 



Bold 



LetterGothi-: 



Scientific 



Scientific Thin 



3 10 0| 14 18 24 



Face |[=fim [ITALICS] | UNDERLINE] [sTR.IKEOUt] 



Portion 



X 



□ 



X 



D 



x x° x x 



Xx°X x 



I'THER. 



!:!h 



, i i . i . i . i I , ' , ' 1 ii i i . 



I 



T 



Figure 3: The property sheet for text characters. 



abolish the CODE key. (We have yet 
to see a computer system with a 
CODE key that doesn't violate the 
principle of visibility.) You never in- 
voke a command or push a key and 
have nothing visible happen. At the 
very least, a message is posted ex- 
plaining that the command doesn't 
work in this context, or it is not im- 
plemented, or there is an error. It is 
disastrous to the user's model when 
you invoke an action and the system 
does nothing in response. We have 
seen people push a key several times 
in one system or another trying to get 
a response. They are not sure whether 
the system has "heard" them or not. 
Sometimes the system is simply 
throwing away their keystrokes. 
Sometimes it is just slow and is queu- 
ing the keystrokes; you can imagine 
the unpredictable behavior that is 
possible. 

We have already mentioned icons 
and windows as mechanisms for 
making the concepts in Star visible. 
Other such mechanisms are Star's 
property and option sheets. Most ob- 
jects in Star have properties. A prop- 
erty sheet is a two-dimensional, form- 
like environment that displays those 
properties. Figure 3 shows the 
character property sheet. It appears 
on the screen whenever you make a 



text selection and push the PROPER- 
TIES key. It contains such properties 
as type font and size; bold, italic, 
underline, and strikeout face; and 
superscript/subscript positioning. In- 
stead of having to remember the 
properties of characters, the current 
settings of those properties, and, 
worst of all, how to change those 
properties, property sheets simply 
show everything on the screen. All 
the options are presented. To change 
one, you point to it with the mouse 
and push a button. Properties in ef- 
fect are displayed in reverse video. 

This mechanism is used for all 
properties of all objects in the system. 
Star contains a couple of hundred 
properties. To keep you from being 
overwhelmed with information, 
property sheets display only the 
properties relevant to the type of ob- 
ject currently selected (e.g., 
character, paragraph, page, graphic 
line, formula element, frame, docu- 
ment, or folder). This is an example 
of "progressive disclosure": hiding 
complexity until it is needed. It is also 
one of the clearest examples of how 
an emphasis on visibility can reduce 
the amount of remembering and typ- 
ing required. 

Property sheets may be thought of 
as an alternate representation for ob- 



262 April 1982 © BYTE Publications Inc 



**« 






m tu -w'* mi ' tsvimm *' 



'THAT WORKS GREAT!" 



Planning an on-time, on-budget proj- 
ect has always been hard work. But 
ournewVisiSchedule™ program can 
help you and your personal computer 
make short work of it. 

The VisiSchedule program is a 
fast and easy way to control projects, 
level resources, meet deadlines, and 
beat cost targets. 

The VisiSchedule program 
instantly shows you the critical path 
among your project's tasks. It allo- 
cates all costs and personnel, and 
specifies earliest/latest start dates, 
slack times, holidays, prerequisites 
and deadlines for each task. And it 
produces summaries, time charts, 
and milestone reports for 
management. 

You can actually develop your 
project as you enter data, investigate 
tradeoffs between manpower, costs 
and time. Ask "what if?" . . . add, 
move, slip or change any task, skill 
level or cost, and the VisiSchedule 

©1982VisiCorp 



program automatically displays the 
impact of your changes. This makes it 
a snap to keep schedules and costs 
current, too. 

While the VisiSchedule program 
does a lot by itself, it can do even 
more for you when used with other 
Visi™ programs. That's because 
they're all inter-related, just like your 
needs and tasks, to give you a fully 
integrated solution. For example, 
automatically transfer the cost data 
toourVisiTrend/Plot™ program 
and analyze cause-and-effect 
relationships. Then instantly 
plot the results in charts and 
graphs for better 
communication. 

In addition, our Mi 
series includes the ^ 
VisiCalc,® 
VisiFile,™ 
VisiDex,™ 
VisiPlot,™ 
VisiTerm™ 



andDesktop/PLAN™ programs. 

Ask your retail computer store 
salesperson for a demonstration of the 
VisiSchedule program. Discover how 
easy it is to make short work of plan- 
ning and budgeting all your work. 

ViSlSCHEDULETROM 
VISICORT 

PERSONAL SOFTWARE"' 




Circle 56 on inquiry card 




Microline 84 (Parallel) 
$1059 88 

DELIVERED 

□ 200 cps bidirectional printing 

□ 50 cps proportional mode 

□ Enhanced/emphasized print 

□ Dot-addressable graphics 

□ Tractor/ friction feed up to 16" 

□ Program-selectable character size 

Microline Printers 

Microline 80 $369 8a 

Microline 82A $484 88 

Microline 83A $749 88 

OKIGRAPH ROM — adds Hi-Res capabilities 
to 82A and 83A Printers $8 QBfl 

NEC Printers 

NEC PC-8023A-C $499 66 

Epson Printers 

MX-80 w/Graftrax $474 88 

MX-80/F-T $569 88 

MX-80/F-T w/Graftrax Sb^ 88 

MX-100 VW* 6 

Graftrax $89 88 

Centronics Printers 

Centronics 739 (Parallel) $539 88 

Centronics 739 (RS-232-C) $644 88 

2-Color Adapter $69 88 

C.ltoh Printers 

C.Itoh Comet I $284 88 

C.Itoh Pro Writer w/3K buffer 

(parallel and serial) $639 88 

C.Itoh F-10 Daisy Wheel 

(40cps) S1564 88 

Cables and interfaces available for the 
Apple, Atari, CBM/PET, and TRS-80 
microcomputers 

Orders & Information: 

CALL (603)-673-8857 
Orders Only: CALL (800)-343-0726 

We accept COD's-No surcharge for credit 
cards-No charge for UPS shipping 
Stock shipments next day-All equip- 
ment factory fresh w/MFG warranty 

Prices subject to change 

HIGH TECHNOLOGY AT AFFORDABLE PRICES 

THE BOTTOM 
■ »LINE 

12 Johnson Street, Milford NH 03055 



mf^r^rr 



EJHPJ 






Search for j 



By matching p^f |TEXT AND PROPERTIES 
In 



EEEES333 



EN TIRE DOCUMENT 



PEST OF DOCUMENT | CURRENT SELECT I 'I'M 



Emm 



langeto j 



By altering "i^ TEXT AN PROPERTIES 'ION FIRM EACH CHANGE 



TTTTTTTTTTTTTTT 



I I IP I I I I I II I II I 'l I I r 



1 



T 



Figure 4: The option sheet for the Find command showing both the Search and 
Substitute options. The last two lines of options appear only when CHANGE IT is 
turned on. 



jects. The screen shows you the visi- 
ble characteristics of objects, such as 
the type font of text characters or the 
names of icons. Property sheets show 
you the underlying structure of ob- 
jects as they make this structure visi- 
ble and accessible. 

Invisibility also plagues the com- 
mands in some systems. Commands 
often have several arguments and op- 
tions that you must remember with 
no assistance from the system. Star 
addresses this problem with option 
sheets (see figure 4), a two-dimen- 
sional, form-like environment that 
displays the arguments to commands. 
It serves the same function for com- 
mand arguments that property sheets 
do for object properties. 

What You See Is What You Get 

"What you see is what you get" (or 
WYSIWYG) refers to the situation in 
which the display screen portrays an 
accurate rendition of the printed 
page. In systems having such 
capabilities as multiple fonts and 
variable line spacing, WYSIWYG re- 
quires a bit-mapped display because 
only that has sufficient graphic power 
to render those characteristics ac- 
curately. 



WYSIWYG is a simplifying tech- 
nique for document-creation systems. 
All composition is done on the 
screen. It eliminates the iterations 
that plague users of document com- 
pilers. You can examine the ap- 
pearance of a page on the screen and 
make changes until it looks right. The 
printed page will look the same (see 
figure 5). Anyone who has used a 
document compiler or post-processor 
knows how valuable WYSIWYG is. 
The first powerful WYSIWYG editor 
was Bravo, an experimental editor 
developed for Alto at the Xerox Palo 
Alto Research Center (see reference 
12). The text-editor aspects of Star 
were derived from Bravo. 

Trade-offs are involved in 
WYSIWYG editors, chiefly having to 
do with the lower resolution of 
display screens. It is never possible to 
get an exact representation of a 
printed page on the screen since most 
screens have only 50 to 100 dots per 
inch (72 in Star), while most printers 
have higher resolution. Completely 
accurate character positioning is not 
possible. Nor is it usually possible to 
represent shape differences for fonts 
smaller than eight points in size since 
there are too few dots per character to 



264 April 1982 © BYTE Publications Inc 



TEK 



2200 SERIES 

DUAL TRACE OSCILLOSCOPES 



THE PERFORMANCE/ 
PRICE STANDARD 




Introducing a direct line 

to a 60 MHz Tektronix scope 

built for your bench! 



From the world's most 
respected name in oscil- 
loscopes: a new scope, 
plus a new direct order 
number, that finally 
makes it practical to put 
Tektronix quality on your 
bench . . .at work or home. 

Among professional en- 
gineers and technicians 
there is no substitute for the 
performance and reliability 
of Tektronix oscilloscopes. 

Now, for the first time, 
Tektronix is offering an ad- 
vanced scope at an un- 
precedented low price — 
and has a direct order line 
that lets you get your order 
processed today! 

The scope: the 2213. 
Its radical new design 
brings you Tektronix 
quality for well below 
what you would pay for 



lesser-name scopes. 

The 2213's practical de- 
sign includes 65% fewer 
mechanical parts, fewer 
circuit boards, electrical 
connectors and cabling. 
Result: a lower price for you 
plus far greater reliability. 

Yet performance is pure 
Tektronix: there's 60 MHz 
bandwidth for digital and 
high-speed analog circuits. 
The sensitivity for low signal 
measurements. The sweep 
speeds for fast logic families. 
A complete trigger system 
for digital, analog or video 
waveforms. And new high- 
performance Tektronix 
probes are included! 

2213 PERFORMANCE 
DATA 

Bandwidth: Two channels, 
dc— 60MHzfrom10V/div 
to 20 mV/div. (50 MHz from 



2 mV/div to 10 mV/div). 
Sweep speeds: Sweeps 
from 0.5 s to 50 ns (to 5 
ns/divwith X10mag). 
Sensitivity: Scale factors 
from 100 V/div(10X probe) 
to 2 mV/div(1X probe). Ac- 
curate to ± 3%. Ac or dc 
coupling. 

Delayed sweep meas- 
urements: Standard 
sweep, intensified after 
delay, and delayed. 
(Need dual time-base 
performance and timing 
accuracy to ± 1.5%? Ask 
about our 2215 priced at 
$1400.) 

Complete trigger system: 
Modes include TV field, 
normal, vertical mode, and 
automatic; internal, exter- 
nal, and line sources; vari- 
able holdoff. 
Probes: High perform- 



ance, positive attachment, 
10-14 pF and 60 MHz at the 
probe tip. 

The price: Just $1100 
complete*. Order direct 
from Tektronix National 
Marketing Center. Phones 
are staffed by technical 
people toansweryour 
questions about the 2213. 
Your direct order includes a 
15-day return policy and full 
Tektronix warranty. 

Now it's easier than 
ever to get your hands on 
a Tek scope! 

ORDER TOLL-FREE 

800-547-1845 

Ask for Department 100 

(In Oregon, Alaska and 
Hawaii: 1-503-627-5402 
collect.) Lines are open 
from 8 am EST to 5 pm PST 



•Price RO.B.. Beaverton. OR. 



Tfektronix 

COMMITTED TO EXCELLENCE 



Copyright©1982 Tektronix, Inc. All rights reserved. 121 



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XEROX 

8010 Star Information System 

User-Interface Design 

To make it easy to compose text and graphics, 
to do electronic filing;, printing;, and mailing; 
all at the same workstation, requires a 
revolutionary user-interface design, 

Bit- map display - Each of the 827,392 dots on 
the screen is mapped to a bit in memory; thus, 
arbitrarily complex images can be displayed, 
STAR, displays all fonts and graphics as they 
will be printed, In addition, familiar office 
object? such as documents, folder?, file 
drawers and in -baskets are portrayed as 
recognizable images, . 

The mourn - A unique pointing device that 
allows the user to quickly select any text, 
graphic or office object cm the display. 

See and Point 

All Star functions are visible to the user on 
the keyboard or on the screen, The user does 
filing and retrieval by selecting them with 
the mo use and touching the MOVE, COPY, 
DELETE or PROPERTIES cum m and keys, Text 
and graphics are edited with the same keys, 



J 



C 









; pi 

'.. til 













DISPLAY: familiar 
office objects 



i i i i i i i i 



IB 



MOUSE: select 
objects, menus 



KEYBOARD; <&**, 



100 r— 



Productivity under the old and the new 

old 




Shorter Production Times 

Experience at Xerox with prototype work- 
stations has shown shorter production times 
and lower costs, The following equation 
expresses thi si. 



gW <33 



1W 



ICO 

\T -. t 

Star users are likely to do more of their own 
composition and layout, controlling the entire 
process including printing and distribution. 

Text and Graphics 

To replace typesetting. Star offers a choice of 
type fonts and sizes, from S point to 24 point, 

Ho** is - seJitftJi'KC'fS-p'i'Uitte-l 

Her* is a sent'Siic* of 10 -point text, 

Here is a sentence of 12 -point text. 

Here is a sentence of 14-point text, 

Here is a sentence of 18-point 
text. 



i ii i i i i i i i i i i i i i ii I i miiii i i i i i i ii ii ii ill i ll ill i i i i i 



Figure 5: A Star document showing multicolumn text, graphics, and formulas. This is the way the document appears on the screen. It 
is also the way it will print (at higher resolution, of course). 



266 April 1982 © BYTE Publications Inc 



Circle 140 on inquiry card. - 



Although the Datasouth DS180 matrix printer may not exactly rate as a work of art, our customers have a very 
high opinion of its value. Over the past year, we have shipped thousands of DS180 printers to customers throughout 
the world. Many of our sales now come in the form of repeat business— a strong testimonial to the acceptance of 
a product. 

The success of the DS180 in a very competitive market did not happen by accident; rather through our sensitivity 
to the needs of the industry. This sensitivity we carry through research and development, production and quality con- 
trol and finally to after sales support and service. 

Recently we introduced new enhancements to make the DS180 printer even more versatile. Dot addressable raster 
scan graphics produces output of computer generated charts, maps and graphs at a resolution of 75 x 72 dots per 
inch. Variable horizontal pitch selection allows printing at 10, 12 
or 16.5 characters per inch plus double wide printing at 5, 6 or 
8.25 characters per inch. The expanded 2K FIFO print buffer 
handles a full CRT screen dump at up to 9600 baud without de- 
laying the host system. We also offer transparent mode for isolat- 
ing communications problems, and for APL users, the dual ASCII/ 
APL character set option. 

Check our list of features and we think you will agree that the DS 1 80 
offers the most complete performance package in matrix printers. 



DS180 PRINTER STANDARD FEATURES 

• Microprocessor Control • Vertical Tabs 

• 180 CPS Print Speed • Perforation Skip-Over 

• Bidirectional/Logic Seeking • Auto Line Feed 

• 1000 Character Buffer (Expandable) . 6/8 LPI 



OPTIONAL FEATURES 

• Compressed Print — 10, 12. 

• High Resolution Dot — 
Addressable Graphics 

• 2k Expanded Print Buffer 




Expanded Charact 


ers 


• 5 IF 


'S Paper Slei 


Adjustable Printhe 


ad/l-6Copie 


s • Par, 


all el and Seri 


% ASCII Charactt 


rSet 


• 110 


•9600 Baud 


Cartridge Ribbon 




• Ten 


ninal Status 


132 Column Print 


Width 


• Auc 


io Ala mi 


Tractor Feed (Fron 


tor Bottom) 


• Self 


■Test 


Non -Volatile Fonn 


at Retention 


.X-o 


n. X'off 


Too of Form 




• Par 


erOut Detec 



) End of Line Carriage Return . APL/ ASCII Che 



d Communications 



The DS180 is available nationwide through our 
network of sales/service distributors. 



s&x 




gf*rORMfiNCE 





mi - * I I ■ 



Jug; 




x^ 2 




computer corporation 

P.O. Box 240947 • Charlotte, NC 28224 • 704/523-8500 



be recognizable. Even 10-point ("nor- 
mal" size) fonts may be uncomfort- 
ably small on the screen, necessitating 
a magnified mode for viewing text. 
WYSIWYG requires very careful 
design of the screen fonts in order to 
keep text on the screen readable and 
attractive. Nevertheless, the increase 
in productivity made possible by 
WYSIWYG editors more than 
outweighs these difficulties. 

Universal Commands 

Star has a few commands that can 
be used throughout the system: 
MOVE, COPY, DELETE, SHOW 
PROPERTIES, COPY PROPERTIES, 
AGAIN, UNDO, and HELP. Each 
performs the same way regardless of 
the type of object selected. Thus, we 
call them "universal" or "generic" 
commands. For example, you follow 
the same set of actions to move text in 
a document and to move a line in an 
illustration or a document in a folder: 
select the object, push the MOVE 
key, and indicate a destination. 



(HELP and UNDO don't use a selec- 
tion.) Each generic command has a 
key devoted to it on the keyboard. 

These commands are far more 
basic than the commands in other 
computer systems. They strip away 
the extraneous application-specific 
semantics to get at the underlying 
principles. Star's generic commands 
derive from fundamental computer- 
science concepts because they also 
underlie operations in programming 
languages. For example, much pro- 
gram manipulation of data structures 
involves moving or copying values 
from one data structure to another. 
Since Star's generic commands em- 
body fundamental underlying con- 
cepts, they are widely applicable. 
Each command fills a variety of 
needs, meaning fewer commands are 
required. This simplicity is desirable 
in itself, but it has another subtle ad- 
vantage: it makes it easy for users to 
form a model of the system. People 
can use what they understand. Just as 
progress in science derives from sim- 



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pie, clear theories, progress in the 
usability of computers is coming to 
depend on simple, clear user inter- 
faces. 

MOVE is the most powerful com- 
mand in the system. It is used during 
text editing to rearrange letters in a 
word, words in a sentence, sentences 
in a paragraph, and paragraphs in a 
document. It is used during graphics 
editing to move picture elements, 
such as lines and rectangles, around 
in an illustration. It is used during 
formula editing to move mathemati- 
cal structures, such as summations 
and integrals, around in an equation. 
It replaces the conventional "store 
file" and "retrieve file" commands; 
you simply move an icon into or out 
of a file drawer or folder. It eliminates 
the "send mail" and "receive mail" 
commands; you move an icon to an 
out-basket or from an in-basket. It 
replaces the "print" command; you 
move an icon to a printer. And so 
on. MOVE strips away much of the 
historical clutter of computer com- 
mands. It is more fundamental than 
the myriad of commands it replaces. 
It is simultaneously more powerful 
and simpler. 

Much simplification comes from 
Star's object-oriented interface. The 
action of setting properties also re- 
places a myriad of commands. For ex- 
ample, changing paragraph margins 
is a command in many systems. In 
Star, you do it by selecting a 
paragraph object and setting its 
MARGINS property. (For more in- 
formation on object-oriented lan- 
guages, see the August 1981 BYTE.) 

Consistency 

Consistency asserts that mecha- 
nisms should be used in the same way 
wherever they occur. For example, if 
the left mouse button is used to select 
a character, the same button should 
be used to select a graphic line or an 
icon. Everyone agrees that consisten- 
cy is an admirable goal. However, it 
is perhaps the single hardest 
characteristic of all to achieve in a 
computer system. In fact, in systems 
of even moderate complexity, con- 
sistency may not be well defined. 

A question that has defied consen- 



268 April 1982 © BYTE Publications Inc 



Circle 70 on inquiry card. 



Circle 294 on inquiry card. « 



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sus in Star is what should happen to a 
document after it has been printed. 
Recall that a user prints a document 
by selecting its icon, invoking 
MOVE, and designating a printer 
icon. The printer absorbs the docu- 
ment, queuing it for printing. What 
happens to that document icon after 
printing is completed? The two 
plausible alternatives are: 

1. The system deletes the icon. 

2. The system does not delete the 
icon, which leads to several further 
alternatives: 

2a. The system puts the icon back 
where it came from (i.e., where it 
was before MOVE was invoked). 
2b. The system puts the icon at an 
arbitrary spot on the Desktop. 
2c. The system leaves the icon in 
the printer. You must move it out 
of the printer explicitly. 

The consistency argument for the 
first alternative goes as follows: when 
you move an icon to an out-basket, 
the system mails it and then deletes it 
from your Desktop. When you move 
an icon to a file drawer, the system 
files it and then deletes it from your 
Desktop. Therefore, when you move 
an icon to a printer, the system 
should print it and then delete it from 
your Desktop. Function icons should 
behave consistently with one 
another. 

The consistency argument for the 
second alternative is: the user's con- 
ceptual model at the Desktop level is 
the physical-office metaphor. Icons 



are supposed to behave similarly to 
their physical counterparts. It makes 
sense that icons are deleted after they 
are mailed because after you put a 
piece of paper in a physical out- 
basket and the mailperson picks it up, 
it is gone. However, the physical 
analogue for printers is the office 
copier, and there is no notion of 
deleting a piece of paper when you 
make a copy of it. Function icons 
should behave consistently with their 
physical counterparts. 

There is no one right answer here. 
Both arguments emphasize a dimen- 
sion of consistency. In this case, the 
dimensions happen to overlap. We 
eventually chose alternative 2a for 
the following reasons: 

1. Model dominance — The physi- 
cal metaphor is the stronger model at 
the Desktop level. Analogy with 
physical counterparts does form the 
basis for people's understanding of 
what icons are and how they behave. 
Argument 1 advocates an implicit 
model that must be learned; argu- 
ment 2 advocates an explicit model 
that people already have when they 
are introduced to the system. Since 
people do use their existing knowl- 
edge when confronted with new sit- 
uations, the design of the system 
should be based on that knowledge. 
This is especially important if people 
are to be able to intuit new uses for 
the features they have learned. 

2. Pragmatics — It is dangerous to 
delete things when users don't expect 
it. The first time a person labors over 



a document, gets it just right, prints 
it, and finds that it has disappeared, 
that person is going to become very 
nervous, not to mention angry. We 
also decided to put it back where it 
came from (2a instead of 2b or 2c) for 
the pragmatic reason that this in- 
volves slightly less work on the user's 
part. 

3. Seriousness — When you file or 
mail an icon, it is not deleted entirely 
from the system. It still exists in the 
file drawer or in the recipients' in-bas- 
kets. If you want it back, you can 
move it back out of the file drawer or 
send a message to one of the recip- 
ients asking to have a copy sent back. 
Deleting after printing, however, is 
final; if you move a document to a 
printer and the printer deletes it, that 
document is gone for good. 

One way to get consistency into a 
system is to adhere to paradigms for 
operations. By applying a successful 
way of working in one area to other 
areas, a system acquires a unity that 
is both apparent and real. Paradigms 
that Star uses are: 

• Editing — Much of what you do in 
Star can be thought of as editing. In 
addition to the conventional text, 
graphics, and formula editing, you 
manage your files by editing filing 
windows. You arrange your working 
environment by editing your Desk- 
top. You alter properties by editing 
property sheets. Even programming 
can be thought of as editing data 
structures (see reference 16). 

• Information retrieval — A lot of 



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270 April 1982 © BYTE Publications Inc 



Circle 198 on Inquiry card. 



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\ Keyboard Interpretation \ 



EKE 



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Figure 6: 77?e keyboard-interpretation window serves as the source of characters that may be entered from the keyboard. The 
character set shown here contains a variety of office symbols. 



power can be gained by applying in- 
formation-retrieval techniques to in- 
formation wherever it exists in a sys- 
tem. Star broadens the definition of 
"database." In addition to the tradi- 
tional notion as represented by its 
record files, Star views file drawers as 
databases of documents, in-baskets as 
databases of mail, etc. This teaches 
users to think of information retrieval 
as a general tool applicable through- 
out the system. 

• Copying — Star elevates the concept 
of "copying" to a high level: that of a 
paradigm for creating. In all the vari- 



ous domains of Star, you create by 
copying. Creating something out of 
nothing is a difficult task. Everyone 
has observed that it is easier to 
modify an existing document or pro- 
gram than to write it originally. 
Picasso once said, "The most awful 
thing for a painter is the white can- 
vas ... To copy others is nec- 
essary." (See reference 20.) Star 
makes a serious attempt to alleviate 
the problem of the "white canvas" by 
making copying a practical aid to 
creation. For example, you create 
new icons by copying existing ones. 



Graphics are created by copying 
existing graphic images and modify- 
ing them. In a sense, you can even 
type characters in Star's 2 16 -character 
set by "copying" them from keyboard 
windows (see figure 6). 

These paradigms change the very 
way you think. They lead to new 
habits and models of behavior that 
are more powerful and productive. 
They can lead to a human-machine 
synergism . 

Star obtains additional consistency 
by using the class and. subclass no- 



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Circle 315 on inquiry card. 



tions of Simula (see reference 4) and 
Smalltalk (see reference 11). The 
clearest example of this is classifying 
icons at a higher level into data icons 
and function icons. Data icons repre- 
sent objects on which actions are per- 
formed. Currently, the three types 
(i.e., subclasses) of data icons are 
documents, folders, and record files. 
Function icons represent objects that 
perform actions. Function icons are 
of many types, with more being 
added as the system evolves: file 
drawers, in- and out-baskets, 
printers, floppy-disk drives, calcula- 
tors, terminal emulators, etc. 

In general, anything that can be 
done to one data icon can be done to 
all, regardless of its type, size, or 
location. All data icons can be 
moved, copied, deleted, filed, mailed, 
printed, opened, closed, and a variety 
of other operations applied. Most 
function icons will accept any data 
icon; for example, you can move any 
data icon to an out-basket. This use 
of the class concept in the user-inter- 
face design reduces the artificial 



distinctions that occur in some sys- 
tems. 

Simplicity 

Simplicity is another principle with 
which no one can disagree. Obvious- 
ly, a simple system is better than a 
complicated one if they have the same 
capabilities. Unfortunately, the world 
is never as simple as that. Typically, a 
trade-off exists between easy novice 
use and efficient expert use. The two 
goals are not always compatible. In 
Star, we have tried to follow Alan 
Kay's maxim: "simple things should 
be simple; complex things should be 
possible." To do this, it was some- 
times necessary to make common 
things simple at the expense of un- 
common things being harder. Sim- 
plicity, like consistency, is not a 
clear-cut principle. 

One way to make a system appear 
simple is to make it uniform and con- 
sistent, as we discussed earlier. 
Adhering to those principles leads to 
a simple user's model. Simple models 
are easier to understand and work 



with than intricate ones. 

Another way to achieve simplicity 
is to minimize the redundancy in a 
system. Having two or more ways to 
do something increases the complexi- 
ty without increasing the capabilities. 
The ideal system would have a mini- 
mum of powerful commands that ob- 
tained all the desired functionality 
and that did not overlap. That was 
the motivation for Star's "generic" 
commands. But again the world is not 
so simple. General mechanisms are 
often inconvenient for high-frequen- 
cy actions. For example, the SHOW 
PROPERTIES command is Star's gen- 
eral mechanism for changing prop- 
erties, but it is too much of an inter- 
ruption during typing. Therefore, we 
added keys to optimize the changing 
of certain character properties: 
BOLD, ITALICS, UNDERLINE, 
SUPERSCRIPT, SUBSCRIPT, 
LARGER/SMALLER (font), 

CENTER (paragraph). These signifi- 
cantly speed up typing, but they don't 
add any new functionality. In this 
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274 April 1982 © BYTE Publications Inc 



Circle 226 on inquiry card. 



The Alternative 
BASIS 108 




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TWX: 910-590-8000 



1982 BASIS, INC. 



Circle 50 on inquiry card. 



it because typing is a frequent activi- 
ty. "Minimum redundancy" is a good 
but not absolute guideline. 

In general, it is better to introduce 
new general mechanism s by which 
"experts" can obtain accelerators 
rather than add a lot of special one- 
purpose-only features. Star's mecha- 
nisms are discussed below under 
"User Tailorability." 

Another way to have the system as 
a whole appear simple is to make 
each of its parts simple. In particular, 
the system should avoid overloading 
the semantics of the parts,. Each part 
should be kept conceptually clean. 
Sometimes, this may involve a major 
redesign of the user interface. An ex- 
ample from Star is the mouse, which 
has been used on the Alto for eight 
years. Before that, it was usee] on the 
NLS system at Stanford Research In- 
stitute (see reference 5). All of those 
mice have three buttons on top. Star 
has only two. Why did we depart 
from "tradition"? We observed that 
the dozens of Alto programs all had 
different semantics for the mouse but- 
tons. Some used them one way, some 
another. There was no consistency 
between systems. Sometimes, there 
was not even consistency within a 
system. For example, Bravo uses the 
mouse buttons for selecting text, 
scrolling windows, and creating and 
deleting windows, depending on 
where the cursor is when you push a 
mouse button. Each of the three but- 
tons has its own meaning in each of 
the different regions. It is difficult to 
remember which button does what 
where. 

Thus, we decided to simplify the 
mouse for Star. Since it is apparently 
quite a temptation to overload the 
semantics of the buttons, we 
eliminated temptation by eliminating 
buttons. Well then, why didn't we use 
a one-button mouse? Here the plot 
thickens. We did consider and pro- 
totype a one-button mouse interface. 
One button is sufficient (with a little 
cleverness) to provide all the func- 
tionality needed in a mouse. But 
when we tested the interface on najve 
users, as we did with a variety of 
features, we found that they had a lot 
of trouble making selections with it. 



In fact, we prototyped and tested six 
different semantics for the mouse but- 
tons: one one-button, four two- 
button, and a three-button design. 
We were chagrined to find that while 
some were better than others, none of 
them was completely easy to use, 
even though, a priori, it seemed like 
all of them would work! We then 
took the most successful features of 
two of the two-button designs and 
prototyped and tested them as a 
seventh design. To our relief, it not 
only tested better than any of the 
other six, everyone found it simple 
and trouble-free to use. 

This story has a couple of morals: 

• The intuition of designers is error- 
prone, no matter how good or bad 
they are. 

• The critical parts of a system should 
be tested on representative users, 
preferably of the "lowest common 
denominator" type. 

• What is simplest along any one 
dimension (e.g., number of buttons) 
i s not necessarily conceptually 
simplest for users; in particular, 
minimizing the number of keystrokes 
may not make a system easier to use. 

Modeless Interaction 

Larry Tesler defines a mode as 
follows: 

A mode of an interactive computer 
system is a state of the user interface 
that lasts for a period of time, is not 
associated with any particular object, 
and has no role other than to place an 
interpretation on operator input. 
(See reference 18.) 

Many computer systems use modes 
because there are too few keys on the 
keyboard to represent all the avail- 
able commands. Therefore, the inter- 
pretation of the keys depends on the 
mode or state the system is in. Modes 
can and do cause trouble by making 
habitual actions cause unexpected 
results. If you do not notice what 
mode the system is in, you may find 
yourself invoking a sequence of com- 
mands quite different from what you 
had intended. 

Our favorite story about modes, 
probably apocryphal, involves 



Bravo. In Bravo, the main typing 
keys are normally interpreted as com- 
mands. The "i" key invokes the Insert 
command, which puts the system in 
"insert mode." In insert mode, Bravo 
interprets keystrokes as letters. The 
story goes that a person intended to 
type the word "edit" into his docu- 
ment, but he forgot to enter insert 
mode first. Bravo interpreted "edit" 
as the following commands: 

E(verything) select everything in 

the document 
D(elete) delete it 

I(nsert) enter insert mode 

t type a "t" 

The entire contents of the document 
were replaced by the letter "t." Jhis 
makes the point, perhaps too strong- 
ly, that modes should be introduced 
into a user interface with caution, if 
at all. 

Commands in Star take the form of 
noun-verb. You specify the object of 
interest (the noun) and then invoke a 
command to manipulate it (the verb). 
Specifying an object is called "making 
a selection." Star provides powerful 
selection mechanisms that reduce the 
number and complexity of commands 
in the system. Typically, you will ex- 
ercise more dexterity and judgment in 
making a selection than in invoking a 
command. The object (noun) is 
almost always specified before the ac- 
tion (verb) to be performed. This 
helps make the command interface 
modeless; you can change your mind 
as to which object to affect simply by 
making a new selection before invok- 
ing the command. No "accept" func- 
tion is needed to terminate or confirm 
commands since invoking the com- 
mand is the last step. Inserting text 
does not even require a command; 
you simply make a selection and 
begin typing. The text is placed after 
the end of the selection. 

The noun-verb command form 
does not by itself imply that a com- 
mand interface is modeless. Bravo 
also uses the noun-verb form; yet, it 
is a highly modal editor (although the 
latest version of Bravo has drastically 
reduced its modalness). The dif- 
ference is that Bravo tries to make 



276 April 1982 © BYTE Publications Inc 






THE ULTIMATE IN COMPUTER CHESS - THE MATE 



THE MATE FOR YOUR MICRO 

PMK Associates, one of the world's 
largest dealers of computer chess systems, 
is pleased to introduce an extraordinary 
new product for the computer chess en- 
thusiast. The Mate is a strategy game 
peripheral for your Apple II * , TRS-80t or 
PET* (TRS-80 and PET versions not 
available until June 4 82) . 

It comes complete with the strongest 
chess program, by far, ever available for a 
microcomputer (requires 32K) , plus a 
true, magnetic sensor chessboard with 
magnetic pieces. All you do is move the 
pieces. The Mate senses your move, 
enters it into the computer, shows the 
move on its high-resolution graphic display 
and responds by lighting two LEDs. There 
are no distracting codes to type in during a 
game, and no need to apply pressure on 
the squares of the board. 

UNPRECEDENTED FLEXIBILITY 

Developed by Applied Concepts, Inc., 
whose $600 MCT chess computer was 
ranked number one in playing strength in 
Chess Life's January '82 issue, The Mate 
also incorporates a wide variety of 
features: 9 levels of play, opening library 
of over 6,000 moves, computer thinks on 
opponent's time, Best/Randomize move 
selection, move suggestions, audio 
On/Off, move erasing, change sides dur- 



ing game, reverse board, watch replay of 
finished game, printout entire game. And 
for hobbyists who want to write their own 
chess programs, full documentation of the 
interface software is provided. 




■ Apple II TM of Apple Computer Inc 



t TRS-BO TM of Tandy Co«p. 



As ACI continues to develop new, 
stronger chess programs your system can 
be easily upgraded. And additional pro- 
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strategy games will soon be available. The 
Mate comes complete with sensory board, 
magnetic chess pieces, plug-in computer 
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game program on cassette or disk and 
operation/programming manual for just 
$269.95. 

FREE BONUS BOOK 

Each unit is covered by our 15-day 
home trial, money-back guarantee. And 

t PET TM of Commodore Business Machines 

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we will promptly exchange any defective 
unit still under the manufacturer's 90 day 
warranty. We maintain a large inventory, 
and most orders are shipped within 48 
hours of receipt. Order before August '82 
and we will include, free of charge, the 
chess classic Bobby Fischer Teaches Chess 
developed in cooperation with Xerox 
Learning Systems. 

There is no game for your micro more 
stimulating than chess, and in computer 
chess there is nothing more powerful than 
The Mate. 

To order, mail your check to: PMK 
Associates, PO Box 598, East Brunswick, 
NJ 08816 (please include $5.00 for 
shipping; NJ residents please add 5% 
sales tax; include $10.00 extra for disk 
format) . Customers in Alaska, Hawaii and 
foreign countries please contact us for 
shipping charges. For fastest service, credit 
card holders may use our 24 hour Toll 
Free order number - 

1-800-835-2246 
aak for Carol 

Please call (201)246-7680 for technical 
questions and further information. 

DEALER INQUIRIES INVITED 



PALMER, 
VgBRIDE 

kMaid 

ASSOCIATES 



COMPUTER AND 
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FOR THE HOME 

P.O. BOX 598 
EAST BRUNSWICK 
NEW JERSEY 08816 

(201) 246-7680 

24 HOURS A DAY 



Actual Size 



t t £ fi <- ? 



Double Size 



t £ fi S 



Normal 



Move 


Copy 


Copy Properties 


Menu 


Illegal 


mode 


mode 


mode 


selecting 


destination 



Graphics 



Figure 7: Some of the cursor shapes used by the Star to indicate the state of the system. The cursor is a 16- by 16-bit map that can be 
changed under program control. 



one mechanism (the main typing 
keys) serve more than one function 
(entering letters and invoking com- 
mands). This inevitably leads to con- 
fusion. Star avoids the problem by 
having special keys on the keyboard 
devoted solely to invoking functions. 
The main typing keys only enter 
characters. (This is another example 
of the simplicity principle: avoid 
overloading mechanisms with mean- 
ings.) 

Modes are not necessarily bad. 
Some modes can be helpful by simpli- 
fying the specification of extended 
commands. For example, Star uses a 
"field fill-in order specification 
mode." In this mode, you can specify 
the order in which the NEXT key will 
step through the fields in the docu- 
ment. Invoking the SET FILL-IN 
ORDER command puts the system in 
the mode. Each field you now select is 
added to the fill-in order. You ter- 
minate the mode by pushing the 
STOP key. Star also utilizes tem- 
porary modes as part of the MOVE, 
COPY, and COPY PROPERTIES 
commands. For example, to move an 
object, you select it, push the MOVE 
key that puts the system in "move 
mode," and then select the destina- 
tion. These modes work for two rea- 
sons. First, they are visible. Star posts 
a message in the Message Area at the 
top of the screen indicating that a 
mode is in effect. The message re- 
mains there for the duration of the 
mode. Star also changes the shape of 



the cursor as an additional indication. 
You can always tell the state of the 
system by inspection (see figure 7). 
Second, the allowable actions are 
constrained during modes. The only 
action that is allowed — except for ac- 
tions directly related to the mode — is 
scrolling to another part of the docu- 
ment. This constraint makes it even 
more apparent that the system is in an 
unusual state. 

User Tailorability 

No matter how general or powerful 
a system is, it will never satisfy all its 
potential users. People always want 
ways to speed up often-performed 
operations. Yet, everyone is different. 
The only solution is to design the sys- 
tem with provisions for user extensi- 
bility built in. The following mecha- 
nisms are provided by Star: 

•You can tailor the appearance of 
your system in a variety of ways. The 
simplest is to choose the icons you 
want on your Desktop, thus tailoring 
your working environment. At a 
more sophisticated level, a work sta- 
tion can be purchased with or with- 
out certain functions. For example, 
not everyone may want the equation 
facility. Xerox calls this "product fac- 
toring." 

• You can set up blank documents 
with text, paragraph, and page layout 
defaults. For example, you might set 
up one document with the normal 
text font being 10-point Classic and 



another with it being 12-point 
Modern italic. The documents need 
not be blank; they may contain fixed 
text and graphics, and fields for vari- 
able fill-in. A typical form might be a 
business-letter form with address, ad- 
dressee, salutation, and body fields, 
each field with its own default text 
style. Or it might be an accounting 
form with lines and tables. Or it 
might be a mail form with To, From, 
and Subject fields, and a heading 
tailored to each individual. Whatever 
the form or document, you can put it 
on your Desktop and make new in- 
stances of it by selecting it and invok- 
ing COPY. Thus, each form can act 
like a "pad of paper" from which new 
sheets can be "torn off." 

Interesting documents to set up are 
"transfer sheets," documents contain- 
ing a variety of graphics symbols 
tailored to different applications. For 
example, you might have a transfer 
sheet containing buildings in different 
sizes and shapes, or one devoted to 
furniture, animals, geometric shapes, 
flowchart symbols, circuit com- 
ponents, logos, or a hundred other 
possibilities. Each sheet would make 
it easier to create a certain type of il- 
lustration. Graphics experts could 
even construct the symbols on the 
sheets, so that users could create 
high-quality illustrations without 
needing as much skill. 
• You can tailor your filing system by 
changing the sort order in file drawers 
and folders. You can also control the 



278 April 1982 © BYTE Publications Inc 



TRS-80* COMPUTING EDITION 



©1981 Percom Data Co., Inc. 



tKtje $ercom ^ertpfteral 



35 cents 



Percom's DOUBLERir tolerates wide variations in media, drives 



GARLAND, TEXAS — May 22, 1981 — 
Harold Mauch, president of Percom Data 
Company, announced here today that an im- 
proved version of the Company's innovative 
DOUBLER® adapter, a double-density plug-in 
module for TRS-80' Model I computers, is 
now available. 

Reflecting design refinements based on both 
theoretical analyses and field testing, the 
DOUBLER II®, so named, permits even great- 
er tolerance in variations among media and 
drives than the previous design. 

Like the original DOUBLER, the DOU- 
BLER II plugs into the drive controller IC 
socket of a TRS-80 Model I Expansion Inter- 
face and permits a user to run either single- or 
double-density diskettes on a Model I. 

With a DOUBLER II installed, over four 
times more formatted data — as much as 364 
Kbytes — can be stored on one side of a five- 
inch diskette than can be stored using a stan- 
dard Tandy Model I drive system. 

Moreover, a DOUBLER II equips a Model I 
with the hardware required to run Model III 
diskettes. 

(Ed. Note: See "OS-80® Bridging the TRS- 
80* software compatibility gap" elsewhere on 
this page. ) 

The critical clock-data separation circuitry 
of the DOUBLER II is a proprietary design 
called a ROM -programmed digital phase-lock 
loop data separator. 

According to Mauch, this design is more 
tolerant of differences from diskette to diskette 
and drive to drive, and also provides immunity 
to performance degradation caused by circuit 
component aging. 




Percom DOUBLER II 



Mauch said "A DOUBLER II will operate 
just as reliably two years after it is installed as it 
will two days after installation." 

The digital phase-lock loop also eliminates 
the need for trimmer adjustments typical of 
analog phase-lock loop circuits, 

"You plug in a Percom DOUBLER II and 
then forget it," he said. 

The DOUBLER II also features a refined 
Write Precompensation circuit that more 
effectively minimizes the phenomena of bit- 
and peak-shifting, a reliability-impairing char- 
acteristic of magnetic data recording. 

The DOUBLER 11, which is fully software 
compatible with the previous DOUBLER, is 
supplied with DBLDOS*, a TRSDOS* 
compatible disk operating system. 

The DOUBLER II sells for %T&&> includ- 
ing the DBLDOS diskette. 



ig system. 
lsfor$Z^C5,includ- 



Circuit misapplication causes diskette read, format problems. 

High resolution key to reliable data separation 



GARLAND, TEXAS — The Percom 
SEPARATOR® does very well for the Radio 
Shack TRS-80* Model I computer what the 
Tandy disk controller does poorly at best: reli- 
ably separates clock and data signals during 
disk-read operations. 

Unreliable data-clock separation causes for- 
mat verification failures and repeated read 
retries. 

CRCERROR-TRACKLOCKEDOUT 

The problem is most severe on high-number 
(high-density) inner file tracks. 

As reported earlier, the clock-data separa- 
tion problem was traced by Percom to misap- 
plication of the internal separator of the 1771 
drive controller IC used in the Model I. 

The Percom Separator substitutes a high- 
resolution digital data separator circuit, one 
which operates at 16 megahertz, for the low- 
resolution one-megahertz circuit of the Tandy 
design. 

Separator circuits that operate at lower 
frequencies — for example, two- or four- 



megahertz — were found by Percom to provide 
only marginally improved performance over 
the original Tandy circuit. 

The Percom solution is a simple adapter that 
plugs into the drive controller of the Expansion 
Interface (EI). 

Not a kit — some vendors supply an un- 
tested separator kit of resistors, ICs and other 
paraphernalia that may be installed by mod- 
ifying the computer — the Percom 
SEPARATOR is a fully assembled, fully tested 
plug-in module. 

Installation involves merely plugging the 
SEPARATOR into the Model I EI disk con- 
troller chip socket, and plugging the controller 
chip into a socket on the SEPARATOR. 

The SEPARATOR, which sells for only 
$29.95 , may be purchased from authorized Per- 
com retailers or ordered directly from the fac- 
tory. The factory toll-free order number is 
1-800-527-1222. 

Ed. note: Opening the TRS-80 Expansion In- 
terface may void the Tandy limited 90-day 
warranty. Circle 326 on inquiry card. 



The Percom DOUBLER II is available from 
authorized Percom retailers, or may be ordered 
direct from the factory. The factory toll-free 
order number is 1-800-527-1222. 

Ed. note: Opening the TRS-80 Expansion In- 
terface may void the Tandy limited 90-day 
warranty. Circle 327 on inquiry card. 

All that glitters is not gold 

OS-80® Bridging the TRS-80* 
software compatibility gap 

Compatibility between TRS-80* Model I diskettes 
and the new Model III is about as genuine as a gold- 
plated lead Krugerrand. 

True, Model I TRSDOS* diskettes can be read on 
a Model III. But first they must be converted and re- 
recorded for Model III operation. 

And you cannot write to a Model I TRSDOS* dis- 
kette. Not with a Model III. You cannot add a file. 
Delete a file. Or in any way modify a Model I 
TRSDOS diskette with a Model III computer. 

Furthermore, your converted TRSDOS diskettes 
cannot be converted back for Model I operation. 

TRSDOS is a one-way street. And there's no re- 
treating. A point to consider before switching the 
company's payroll to your new Model III. 

Real software compatibility should allow the di- 
rect, immediate interchangeability of Model I and 
Model III diskettes. No read-only limitations, no 
convcrsion/re-recording steps and no chance to be 
left high and dry with Model III diskettes that can't 
be run on a Model I. 

What's the answer? The answer is Percom's OS- 
80® family of TRS-80 disk operating systems. 

OS-80 programs allow direct, immediate inter- 
changeability of Model I and Model III diskettes. 

You can run Model I single-density diskettes on a 
Model III; install Percom's plug-in DOUBLER^ 
adapter in your Model I, and you can run double- 
density Model III diskettes on a Model I. 

There's no conversion, no re-recording. 

Slip an OS-80 diskette out of your Model I and in- 
sert it directly in a Model III. 

And vice-versa. 

Just have the correct OS-80 disk operating sys- 
tem — OS-80, OS-80D or OS-80/III — in each com- 
puter. 

Moreover, with OS-80 systems, you can add, de- 
lete, and update files. You can read and write disket- 
tes regardless of the system of origin. 

OS-80 is the original Percom TRS-80 DOS for 
BASIC programmers. 

Even OS-80 utilities are written in BASIC. 

OS-80 is the Percom system about which a user 
wrote, in Creative Computing magazine, ". . .the best 
$30.00 you will ever spend."! 

Requiring only seven Kbytes of memory, OS-80 
disk operating systems reside completely in RAM. 
There's no need to dedicate a drive exclusively for a 
system diskette. 

And, unlike TRSDOS. you can work at the track 
sector level, defining and controlling data formats — 
in BASIC — to create simple or complex data struc- 
tures that execute more quickly than TRSDOS files. 

The Percom OS-80 DOS supports single-density 
operation of the Model I computer — price is 
$29.95; the OS-80D supports double-density opera- 
tion of Model I computers equipped with a DOUB- 
LER or DOUBLER II; and, OS-80/III — for the 
Model III of course — supports both single- and 
double-density operation. OS-80D and OS-80/III 
each sell for $49.95. Circle 328 on inquiry card. 



PRICES AND SPECIFICATIONS SUBJECTTOCH ANGE WITHOUTNOTICE. PRICES DO NOT INCLUDE HANDLING AND SHIPPING. 

PERCOM DATA COMPANY, INC 11220 Pagemill Road Dallas, Texas 75243 (214) 340-7081 

^Trademark ofPercom Data Company, Inc. *TRS-80and TR$DOS are trademarks of Tandy Corporation which has no relationship to Percom Data Company. tCreative Computing Magazine, June, 1980, page 26. 



Circle 6 on inquiry card. 




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Additional 
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• Loads and Executes as a normal program under CP/M. 
installing itself under the CP/M operating system 

•Other CP/M programs - editors/word processors/application programs/compilers/ 
assemblers - may then be run using all MicroShell features 

• CP/M compatibility is generally not aflected by MicroShell's presence 

• Adds UNIX Power without losing CP/M Compatibility 



• Send Console Output to a File instead of or in addition to the screen 
Example: stat '.* > status - sends "stat" output to file "status" 

• Take Console Input from a File instead of the Keyboard 

Example: ed filename < script - takes "ed" commands from the file "script" 

• Indispensable for: graphic debugging, saving exact Screen Output for documentation, etc. 



• MicroSheil finds your program. User concentrates on the big tasks, MicroShell does the details 
Permits development or data files on one drive and all programs on another 

■ User-specified file types for Automatic Search. Example: ".com", ".int", etc. 

• User-specified Search Path. Example: Current Drive 1st, then Drive A, etc. 



• User types a logical group of commands to be executed 
Example: compile file; link file; file 

• MicroShell executes the commands one at a time 



■ Files of CP/M or MicroShell commands are executed by MicroShell simply by typing file name 

• User-specified Command Filetypes. Example: ".sh", ".sub", etc. 

• Argument substitution ($1, $2, etc.) as with CP/M SUBMIT/XSUB 



■ User definable prompt with Disk Drive and/or User Number optional 

■ Install program to customize MicroShell to user's needs & system 
• Others - ORDER MANUAL FOR FULL DETAILS 



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filing hierarchy by putting folders in- 
side folders inside folders, to any 
desired level. 

• You can tailor your record files by 
defining any number of "views" on 
them. Each view consists of a filter, a 
sort order, and a formatting docu- 
ment. A filter is a set of predicates 
that produces a subset of the record 
file. A formatting document is any 
document that contains fields whose 
names correspond to those in the 
record file. Records are always dis- 
played through some formatting 
document; they have no inherent ex- 
ternal representation. Thus, you can 
set up your own individual subset(s) 
and appearance (s) for a record file, 
even if the record file is shared by 
several users. 

• You can define "meta operations" 
by writing programs in the Cl/Stomer 
Programming language CUSP. For 
example, you can further tailor your 
forms by assigning computation rules 
expressed in CUSP to fields. Even- 
tually, you will be able to define your 
own commands by placing CUSP 
"buttons" into documents. 

• You can define abbreviations for 
commonly used terms by means of 
the abbreviation definition/expan- 
sion facility. For example, you might 
define "sdd" as an abbreviation for 
"Xerox Systems Development De- 
partment." The expansion can be an 
entire paragraph, or even multiple 
paragraphs. This is handy if you 
create documents out of predefined 
"boilerplate" paragraphs, as the legal 
profession does. The expansion can 
even be an illustration or mathe- 
matical formula. 

• Every user has a unique name used 
for identification to the system, 
usually the user's full name. How- 
ever, you can define one or more 
aliases by which you are willing to be 
known, such as your last name only, 
a shortened form of your name, or a 
nickname. This lets you personalize 
your identification to the rest of the 
network. 

Summary 

In the 1980s, the most important 
factors affecting how prevalent com- 
puter usage becomes will be reduced 



280 April 1982 © BYTE Publications Inc 



Circle 299 on inquiry card. 



For PDP-11 RSX, RSTS/E, and RT-11 users 

l&scal-2 

We can save you time because our Pascal-2 
compiler matches or beats the run-time per- 
formance of any high-level language on the 
PDP-11. The same is true for the size of code 
generated. 

We can save you time because Pascal-2 has 
excellent error reporting and recovery, be- 
cause our interactive, source-level debugger 
helps detect deep-rooted logical errors, and 
because our package includes a number of 
other programmer-oriented utilities. 

We can save you time because the structured 
methods of Pascal encourage problem solv- 
ing the first time round. Team members can 
understand one another's code, thus improv- 
ing communication and protecting you against 
the disruptive effects of staff changes. 



We can save you time, and money, because 
you can take your standard Pascal programs 
with you to a new computer. You may even 
find our Pascal-2 compiler running on that 
new machine. We're working on a VERSAdos 
compiler and a stand-alone system for the 
MC68000. We're field-testing a cross- 
compiler from RSX to VERSAdos and a 
Pascal-2 for UNIX on the PDP-11. We're also 
developing a Pascal-2 for VAX/VMS (where 
our RSX product already runs in compatibility 
mode). 

Call or write. We'll send benchmark details, a 
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MicroPlot™ $395 

100% Tektronix Plot-10 TCS compatible 
graphic package. 

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Supplied with the original Tektronix™ 
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This package enables you to run even, 
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files to be used with Fortran-80™. 



MenuMaster™ $95 

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cost, increased functionality, im- 
proved availability and servicing, 
and, perhaps most important of all, 
progress in user-interface design. The 
first three alone are necessary, but 
not sufficient for widespread use. Re- 
duced cost will allow people to buy 
computers, but improved user inter- 
faces will allow people to use com- 
puters. In this article, we have pre- 
sented some principles and techniques 
that we hope will lead to better user 
interfaces. 

User-interface design is still an art, 
not a science. Many times during the 
Star design we were amazed at the 
depth and subtlety of user-interface 
issues, even such supposedly straight- 
forward issues as consistency and 
simplicity. Often there is no one 
"right" answer. Much of the time 
there is no scientific evidence to sup- 
port one alternative over another, 
just intuition. Almost always there 
are trade-offs. Perhaps by the end of 
the decade, user-interface design will 
be a more rigorous process. We hope 
that we have contributed to that pro- 
gress. ■ 



References 

1. Arnheim, Rudolf. Visual Thinking. 
Berkeley: University of California Press, 
1971. 

2. Brooks, Frederick. The Mythical Man- 
Month. Reading, MA: Addison-Wesley, 
1975. 

3. Card, Stuart, William English, and Betty 
Burr. "Evaluation of Mouse, Rate- 
Controlled Isometric Joystick, Step Keys, 
and Text Keys for Text Selection on a 
CRT." Ergonomics, vol. 21, no. 8, 1978, 
pp. 601-613. 

4. Dahl, Ole-Johan and Kristen Nygaard. 
"SIMULA — An Algol-Based Simulation 
Language." Communications of the 
ACM, vol. 9, no. 9, 1966, pp. 671-678. 

5. Engelbart, Douglas and William English. 
"A Research Center for Augmenting 
Human Intellect." Proceedings of the 
AFIPS 1968 Fall Joint Computer Con- 
ference, vol. 33, 1968, pp. 395-410. 

6. English, William, Douglas Engelhart, and 
M. L. Berman. "Display-Selection Tech- 
niques for Text Manipulation." IEEE 
Transactions on Human Factors in Elec- 
tronics, vol. HFE-8, no. 1, 1967, pp. 
21-31. 

7. Fitts, P. M. "The Information Capacity of 
the Human Motor System in Controlling 
Amplitude of Movement." Journal of Ex- 
perimental Psychology, vol. 47, 1954, pp. 
381-391. 



8. Ingalls, Daniel. "The Smalltalk Graphics 
Kernel." BYTE, August 1981, pp. 
168-194. 

9. Intel, Digital Equipment, and Xerox Cor- 
porations. The Ethernet, A Local Area 
Network: Data Link Layer and Physical 
Layer Specifications. Version 1.0, 1980. 

10. Irby, Charles, Linda Bergsteinsson, 
Thomas Moran, William Newman, and 
Larry Tesler. A Methodology for User In- 
terface Design. Systems Development 
Division, Xerox Corporation, January 
1977. 

11. Kay, Alan and the Learning Research 
Group. Personal Dynamic Media. Xerox 
Palo Alto Research Center Technical 
Report SSL-76-1, 1976. (A condensed 
version is in IEEE Computer, March 
1977, pp. 31-41.) 

12. Lampson, Butler. "Bravo Manual." Alto 
User's Handbook, Xerox Palo Alto Re- 
search Center, 1976 and 1978. (Much of 
the design of all the implementation of 
Bravo was done by Charles Simonyi and 
the skilled programmers in his "software 
factory.") 

13. Metcalfe, Robert and David Boggs. 
"Ethernet: Distributed Packet Switching 
for Local Computer Networks." Com- 
munications of the ACM, vol. 19, no. 7, 
1976, pp. 395-404. 

14. Miller, George. "The Magical Number 
Seven, Plus or Minus Two: Some Limits 
on Our Capacity for Processing Informa- 
tion." In The Psychology of Communica- 
tion, by G. Miller, New York: Basic Books, 
1967. (An earlier version appeared in 
Psychology Review, vol. 63, no. 2, 1956, 
pp. 81-97. 

15. Seybold, Jonathan. "Xerox's 'Star'." In 
The Seybold Report, Media, PA: Seybold 
Publications, vol. 10, no. 16, 1981. 

16. Smith, David Canfield. Pygmalion, A 
Computer Program to Model and Stimu- 
late Creative Thought. Basel, Switzer- 
land: Birkhauser Verlag, 1977. 

17. Smith, David Canfield, Charles Irby, 
Ralph Kimball, and Eric Harslem. "The 
Star User Interface: An Overview." Sub- 
mitted to the AFIPS 1982 National Com- 
puter Conference. 

18. Tesler, Larry. Private communication; but 
also see his excellent discussion of 
modes in "The Smalltalk Environment." 
BYTE, August 1981, pp. 90-147. 

19. Thacker, C. P., E. M. McCreight, B. W. 
Lampson, R. F. Sproull, and D. R. Boggs. 
"Alto: A Personal Computer." In Com- 
puter Structures: Principles and Ex- 
amples, edited by D. Siewiorek, C. G. 
Bell, and A. Newell, New York: McGraw- 
Hill, 1982. 

20. Wertenbaker, Lael. The World of 
Picasso. New York: Time-Life Books, 
1967. 

21. Zloof, M. M. "Query-by-Example." Pro- 
ceedings of the AFIPS 1975 National 
Computer Conference, vol. 44, 1975, pp. 
431-438. 



282 April 1982 © BYTE Publications Inc 



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Designing a Text Editor? 
The User Comes First 

A system's power is measured in ease of use. 



Steven Jong 
38 Riverhurst Road 
Billerica, MA 01821 



I n choosing or designing any com- 
puter system — hardware or soft- 
ware — the most important considera- 
tion is the human interface: if a 
system doesn't work for the user, it's 
not a working system. This article 
presents observations on the crucial 
relationship between human factors 
and the design of text editors for 
video-display terminals. These obser- 
vations are drawn from my ex- 
perience with a number of editors on 
computers of various sizes and from 
software-design and human-factors 
literature. All the features described 
here exist on at least one editor. My 
aim is to give you some things to look 
for if you want to buy — or write — an 
outstanding text editor. 

The first and most important 
design goal is ease of use. This should 
surprise no one. James Martin (see 
reference 7) pointed out back in 1973: 
"To be effective [in the next decade], 
systems will have to be designed from 
the outside in. The terminal or con- 
sole operator, instead of being a 
peripheral consideration, will become 
the tail that wags the whole dog." 
Text editors are, to most users, the 
outermost layer of their computer 
system — the layer they deal with 
most. Timesharing users spend over 
half their time using a text editor, and 



About the Author 

Steven Jong, a principal software tech- 
nical writer, holds a master's degree in 
science communication from Boston 
University. 



editing commands account for about 
fifteen percent of all commands they 
enter. Personal-computer users may 
exceed those figures. Ease of use, 
therefore, weighs most heavily on 
editor design. 

What, then, makes a good text 
editor? Human-factors literature sug- 
gests many characteristics of the 
laudable text editor. Different 
authors espouse perfectly reasonable 
but totally contradictory principles. 
You'll have to evaluate your needs 
when designing one feature in and 
another out (see text box on page 298.) 

Screen Display Features 

Let's consider what you want or 
need to see on the text display. 

The top or bottom display line (but 
not both) should provide program 
and system status information, such 
as the file name, the current file line 
number, the last command invoked, 
the time, and program prompts. This 
keeps you informed as to the system 
state and is well worth the overhead. 
Another line could display the cur- 
rent tab stops and margins, if they are 
to be controlled by the user (see figure 

1). 

When you enter a keystroke in the 
middle of a line of text, one of two 
things may happen. The character at 
the cursor position may be overstruck 
by the new character; or the new 
character may be inserted at the cur- 
sor position and characters from the 
cursor position on move to the right 
to accommodate it. Existing editors 
use both modes, but overstrike 



editors require a separate insert/stop- 
insert function and don't prevent you 
from accidentally replacing text. 
From the user's viewpoint, a display 
mode that allows accidental erasure 
of text is undesirable. 

A screen-editor window is limited 
by the size of the screen. To minimize 
the effects of this limitation and allow 
you to browse through text, there 
must be a command to scroll text, 
both vertically and horizontally (see 
figure 2). (An editor that allows 
horizontal scrolling can display 
overlong lines as truncated, with the 
ends of the lines offscreen, which 
seems most natural.) You should be 
able to scroll through the file con- 
tinuously and stop whenever you 
want. This suggests that scrolling 
should continue as long as some par- 
ticular key is depressed and stop the 
instant the key is released. 

How fast should the display scroll? 
The Honeywell WP 6 word processor 
lets you scroll at the rate of about ten 
lines per second. This allows brows- 
ing, but is slow if you want to 
traverse several screens' worth of 
text. It also limits scrolling to the text 
within the current page of memory. 
The scrolling function built into 
Radio Shack Model II computers gets 
you from one end of a file to the other 
very nicely, but too quickly to read 
anything. It would be nice to scroll 
and also maneuver using some other 
mechanism, such as "go to string," 
"go to page," etc. 

You may want to mark blocks of 
text for movement, reproduction, or 



284 April 1982 © BYTE Publications Inc 





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The wonder computer of the 1980s. The VIC-20 from Commodore, world's 
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I April '81 issue 2 May "81 issue 3 November '81 issue 4 Fall '81 issue 

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Name. 



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Circle 92 on Inquiry card. 



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Dear. Mom, * 



► My. first .day. at .the .computer. camp. has .been. just . swell. . .You. 
wouldrT t .believe .what .these .computers . can. do ! . .And. all. the .kids . 
get . their . own . systems . for . their . very . own ! . . I * m . so . happy . you . and . 
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bet . I .beat .him! ^ 




Love , ^ 
Harold 
PAGE 1 



LINE 16 Press DEL to delete, or RETURN to cancel. 



Figure 1: An idealized screen-editor display. The larger the display area, the better. Spaces, tabs, and carriage returns are indicated 
by special symbols. "5" in the tab line indicates single spacing; "<" indicates that the line length is 64 characters; "!" indicates a tab 
stop. Besides showing its user a window of text, the screen highlights selected blocks, prompts for action, and displays program and 
system status. 



deletion. Text editors on some 
minicomputers display plain text in 
low-intensity characters and mark 
blocks using high-intensity 
characters. Microcomputer-based 
word processors tend to use inverse- 
video characters for the same func- 
tion. 

A useful, advanced feature is 
multifile editing. The best way to 
display multiple files on the screen is 
to use multiple windows. The screen 
can, for instance, be bisected by a line 
of dashes, with one file displayed 
above and the other below. Some 
editors dedicate a portion of the 
screen as a message window for 
prompts and error messages. This 
window should not be too large, of 
course; three or four lines is typical. 

Many text editors employ the beep 
signal, a simple and powerful atten- 



tion-getting device that, unfortunate- 
ly, is often misused. More than one 
word-processing system uses the signal 
in an inconsistent and annoying way: 
beeping when users enter some things 
right (sign-in lines, for instance), and 
yet also beeping when users enter 
some things incorrectly (a function 
key during a search); often they re- 
main silent during many other kinds 
of errors. In my opinion, the beeper is 
best left to signaling errors. 

The coming flood of color com- 
puters will soon bring a generation of 
full-color software. Four colors — red, 
green, blue, and yellow — are prob- 
ably sufficient for text displays; green 
is generally acknowledged as easiest 
on the eyes. Color could highlight a 
search string, an error message, or a 
prompt. Color could also mark por- 
tions of a file. For instance, various 



parts of a document could be marked 
in green (draft), yellow (comments), 
red (technical questions), and so 
forth. However, color should not be 
the only distinguishing feature of im- 
portant messages, because four per- 
cent of the population are color blind. 

Word-Processing Features 

Certain functions apply strictly to 
word processing. One is a dot-filled 
display in which each space character 
is represented by a dot smaller than a 
period. The dots simplify counting 
spaces and aligning text vertically. 
One might argue that a dot-filled 
screen appears too "busy," but most 
users of Wang and Lanier word pro- 
cessors, which feature dot-filled 
screens, are happy with them. 

A good word-processing editor 
should perform "word wrapping", 



286 April 1982 © BYTE Publications Inc 



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Figure 2: Vertical and horizontal scrolling provide a flexible "window" to text. Con- 
ceptually, either the screen or the text can be thought of as moving. 



i.e., a word being typed in that ex- 
ceeds the specified line length is car- 
ried down to start a new line. This 
relieves you of having to decide when 
to end a line. Word wrapping is one 
of the two most useful features of a 
word-processing editor (the other is 
character deletion). It is possible both 
to break lines and justify them at the 
same time; Micropro International's 
Wordstar microcomputer-based 
editor does this. 

When characters are inserted into 
the middle of a line, a word- 
processing editor should reformat the 
rest of the text automatically. In prac- 
tice, this proves difficult. Some 
editors, for instance, temporarily 
clear the screen from the cursor posi- 
tion to the end of the screen during 
text insertion (see figure 3). New text 
can be entered and formatted; when 



the user signals that insertion is 
finished, the rest of the text is refor- 
matted. The ideal editor would refor- 
mat text continuously during inser- 
tion, but I have seen no editor that 
does. Instead, most include a separate 
"reformat" command to reformat the 
current paragraph after insertion is 
finished. 

Navigating Through the File 

Now that we know how to display 
text, we must deal with the problem 
of finding our way through it. Ad- 
dressing text is a prerequisite to 
manipulating text. The more power 
and f lexiblity you have in addressing, 
the better. 

The basic cursor movement is 
"quadridirectional," or up /down/ 
left/right, universally offered by 
screen editors. Boundary conditions, 



however, may vary from one editor 
to the next. For instance, if the cursor 
is in column 1 (the left extreme of the 
screen) and you try to move the cur- 
sor to the left, one screen editor might 
treat your action as an error; another 
editor might oblige the request by 
moving the cursor to the last 
character of the previous line. 

What happens when you try to 
move the cursor past the end of a 
line? Usually, editors will not allow 
cursor movement, or at least text in- 
sertion, past the end of a line. In prac- 
tice this proves a limitation, and there 
is no ease-of-use justification for it. It 
could, in fact, imply an attempt to 
enter spaces (perhaps the user is try- 
ing to make columnar text column by 
column). 

Commands that move the cursor a 
single character at a time are not 
enough. There should also be com- 
mands to move by word, line, 
sentence, paragraph, screen, page im- 
age, and column; the ability to go to 
the top or the bottom of a file at a 
single keystroke is also useful. Com- 
bining cursor-movement commands 
with a Repeat key is also very impor- 
tant (an advanced video terminal 
may include an automatic-repeat 
function if a key is held down). An 
alternative for terminals without 
repeat functions is to allow com- 
mands to accept numeric arguments 
so that a user could, for instance, skip 
four sentences. 

Signaling Commands 

Now we turn to the mechanism by 
which you signal that you are enter- 
ing a command (the nature of which 
is not yet important). Single-char- 
acter command names are best for 
fast typing. Screen editors must use 
nonalphanumeric characters, because 
alphanumeric keystrokes must 
always appear as entered. The next 
simplest arrangement is to use control 
characters, because the CTL (Con- 
trol) key is standard on most com- 
puter keyboards. CTL-W, then, 
might mean "write file." Of course, 
entering some command sequences 
would require two hands. 

Designers of some computer sys- 
tems, thinking of novice users, in- 



288 April 1982 © BYTE Publications Inc 



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DELTA PRODUCTS INC. • 15392 ASSEMBLY LANE, HUNTINGTON BEACH, CA 92649 
(714)898-1492 • MON to FRI - 8 AM to 5 PM • TELEX: 681-367 DELTMAR HTBH 

Circle 145 on inquiry card. 



S. ..!... .1 2 . 

and . slowed . to . a . halt • - 



► Most . of . the . flanges . were . undamaged . by . the . accident « 
However, .the . flanges . closest .to .the . input .valve .were . 
slightly . scratched, .and . those . actually . struck .by. the. 
chain .were .contaminated. with. oil. . .This .was . judged . not . 
serious. . ■ 



TRIPREPORT PAGE 12 LINE 44 We . therefore . recommend . the . following : 




Figure 3: Text insertion on a typical minicomputer-based word processing editor. The screen is cleared from the point of insertion; 
new text is displayed in proper format. The display logic is simpler than for reformatting the screen after every character is entered. 
In the illustration, inserted text is highlighted. 



variably turn to special-function keys 
for signal commands. They feel the 
simplest possible arrangement is to 
give each function its own labeled 
key, reinforcing the what-you-see-is- 
what-you-get nature of screen 
editors. But before assigning all func- 
tions to dedicated keys, a designer 
should consider what adjustments 
skilled typists must make to reach 
function keys located on the 
periphery of a keyboard, and 
whether certain functions are too im- 
portant to be invoked with single 
keystrokes. The rush toward function 
keys in the business market may slow 
as human-factors specialists research 
these questions. In the microcom- 
puter marketplace, function keys are 
uncommon, and a general-purpose 
screen editor would be fatally limited 
if it required function keys. 



Ease-of-use considerations suggest 
the use of prompts for procedural 
commands. If you press the Search 
key on a Wang word processor, the 
system prompts: "For what?" in the 
message window. It searches for 
whatever is typed in response to the 
prompt. Press the Delete key; it 
prompts: "Delete what?" Mark text 
for deletion, and press the Execute 
key to actually delete it. This prompt- 
ing helps beginning users, though in 
time they become conditioned to ig- 
nore the prompts. 

Commands can be assigned to in- 
dividual keys mnemonically, phys- 
ically, or symbolically. For example, 
to signal quadridirectional cursor 
movement, a mnemonic assignment 
scheme could be U, D, L, and R (for 
up, down, left, and right); a physical 
assignment scheme could be W, Z, A, 



and S (spatially simulating a cursor 
keypad — try it on your own key- 
board!); and a symbolic assignment 
scheme could be *, V, <, and > 
(symbolizing arrows). There are 
other possibilities: another mnemonic 
could be F, B, P, and N (forward, 
backward, previous, and next); and 
another physical scheme could be I, J, 
K, and M (for the right hand instead 
of the left). All of these arrangements 
are used on various systems. What- 
ever the scheme, commands must be 
logically arranged, even at the ex- 
pense of leaving out a function 
because there is no reasonable key to 
which it can be assigned. A command 
that is hard to call will be hard to 
remember and, ultimately, hard to 
use. 

If key assignments are not com- 
pletely logical, the results may be 



292 April 1982 © BYTE Publications Inc 



Can any camera 

make you a better 

photographer? 



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While talent, admittedly, 
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When you look into the view 
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finished photograph 
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which will help improve your 
results. 



Formats approx. 
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Hasselblad's 
interchangeability is another 
great creative stimulant. 

Circle 425 on inquiry card. 



It helps you shape the camera 
configuration to suit your own 
ideas, so the camera and your 
mind's eye can work together as 
one. 

For a start, you can interchange 
the film magazine with other 
magazines, permitting changes in 
film types, film capacity and even 
formats. And you can switch 
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out wasting a single shot and that 
includes a Polaroid back. 

You can also interchange the 
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for a wide range of optical 
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creative possibilities. 

You can further adapt your 
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Considering the extra- 
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versatility of the 
Hasselblad, the 
uninitiated might 
be inclined to 
conclude that this 
is a complicated 
camera. But nothing 
could be further 
from the truth. The 
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enabling the photographer to 
concentrate on the subject and not 
on the camera. 

So if you're looking to improve 
your photography, look into a 
Hasselblad. 

See your Hasselblad dealer or 
write for our comprehensive 
brochures, to: 
Victor Hasselblad Inc., 
10 Madison Road, 
Fairfield, N.J. 01006 




-HASStLtsLft 

When you shoot for perfection 



BYTE April 1982 293 



Circle 255 on inquiry card. 



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294 April 1982 © BYTE Publications Inc 



catastrophic. I recall a Boston Univer- 
sity student who some years ago ran 
afoul of the RAX line editor written 
for the school's IBM 360/50 system. 
He went to a computing center ad- 
viser and explained that he was 
searching for what he thought was 
the next line of his file. Although he 
had checked most of his file, he 
couldn't find the elusive line. When 
the adviser examined the file, she dis- 
covered that most of it had been 
deleted. When asked what commands 
he had been using, the student replied 
that he didn't know much about the 
editor, but that U meant go up, and 
didn't D mean go down? It was a 
perfectly reasonable assumption; un- 
fortunately, while U did mean up, N 
(next) meant down, and D meant 
delete. 

The first commands to assign 
should be the basic ones given in table 
1. They form a simple, symmetrical, 
and complete set of editing functions. 
Note that the Search command re- 
quires some sort of command se- 
quence to signal the editor that the 
search string has been specified. The 
Return key is natural for this purpose 
(at the cost of making the Return 
character a difficult string to search 
for). 

Unless the editor handles routine 
file I/O (input/output) operations — 
creating, deleting, reading from, and 
writing to files — expect it to work 
only with an operating system. These 
operations must be invisible to the 
user. 

Idiot-Proofing 

Designers, preoccupied with estab- 
lishing responses to correct key- 
strokes, often neglect incorrect ones. 
Because editors are used so extensive- 
ly they should never abort, no matter 
what you enter. The process of "idiot- 
proofing" interactive programs was 
described by Anthony Wasserman in 
1973 (see reference 11). It involves an- 
ticipating incorrect entries, missing 
input, inadvertent keystrokes (e.g., 
BREAK, CTL, and ESCape), and 
transmission errors (which are rare in 
personal computer terminals). An ex- 
ample of non-idiot-proof hardware is 
found in some versions of the Apple 



II computer keyboard. The Reset key 
is in a hard-to-miss location — just 
above the Return key; many applica- 
tions packages carry warnings never 
to press it while using their programs. 
One magazine printed a letter sug- 
gesting that Apple users place a rub- 
ber grommet beneath the key, to 
make it harder to push. A software 
example of non-idiot-proofing is the 
Electric Pencil I's tendency to drop 
keystrokes entered by fast typists. 
The very point of word processing is 
to increase throughput; a program 
that drops keystrokes invokes 
paranoia in its users and slows them 
down. 

The use of "kill rings" is a nice, 
practical application of idiot-proof- 
ing. Deletions larger than single char- 
acters are not discarded, but stored 
temporarily in a stack. If text is 
deleted by accident, it can be re- 
trieved by a command. This truly 
protects users from themselves. 
Editors with kill rings actually make 
it difficult to lose text. 

Power versus Ease of Use 

In general, the more powerful a 
system is (i.e., the more capabilities it 
has), the more difficult it is to use. 
There are two reasons for this: first, 
the sheer number of commands 
makes them hard to remember; sec- 
ond, it becomes impossible to assign 
commands to keys or names in a con- 
sistent manner. Many editors have 
forty or more commands; for them, 
any single-key naming scheme soon 
collapses. Editors on the market to- 
day delete text at the keystrokes D 
(delete), G (gobble), W (wipe), and K 
(kill). Some compromise between 
power and ease of use is needed. 

Function keys are a liability for a 
powerful editor. Consider the Atex 
typesetting system, on which all func- 
tions are visible as function keys. 
There are, however, 32 function 
keys, and each can be prefixed with 
the shift key and /or a "supershift" 
key — making a total of 128 functions, 
assigned four to a key. Given the 
complexity of typesetting systems 
and the desire to provide an easy-to- 
use system, this end was inevitable. 

What is needed is a hierarchy of 

Circle 269 on inquiry card. — ► 



MICRO-SCI IS IN THE GAME FOR ALL THE APPLES... 






-SCI 




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Micro-Sci has three disk drives and two 
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and performance requirements. 

THE FIRST ACE— A2 

The new A2 is the price/compatibility substitute 
for the Disk ll, ,M intended as the second drive on 
an existing controller, or as a full A2 subsystem. 
The A2 drive or A2 subsystem is an idea) choice 
when the drives will be primarily used for 
entertainment or prepackaged software programs. 
THE SECOND ACE— A40 

The A40 is a price/performance alternative to the 
Disk II. With 40 tracks, you get an additional 20K 
bytes, and faster track-to-track access. The A40 is 
intended for use in dedicated DOS, CP/M and 
Pascal applications, and as a companion drive for 
the A70.The A40 is Micro-Sets most cost-effective 



disk subsystem for the Apple lis. 

THE THIRD ACE— A70 

The A70 is the price/capacity alternative. 
At over a quarter million bytes per drive, the A70 
has the capacity of two Disk lis or an eight-inch 
floppy, but costs only slightly more than a single 
Disk II. One A70 supports a DOS fife as large as 
270K, a CP/M file up to 254K, and 560 blocks 
in Pascal. 

THE PAIR— MICRO-SCI'S CONTROLLERS 

The A2 comes with a unique new controller. 
This controller supports any combination of A2s or 
Disk Us, you have complete flexibility. 

The A40 and A70 share a common controller. 
Mix A40s and A70s in any fashion, one A40 with 
one A70, two A40s or two A70s— all on the 
same controller. 

You can have a Disk II or A2 controller with 



Disk II or A2 drives and still add an A40 or A70 
subsystem. That's full system-level compatibility. 
THE PAT HAND 

Versatility, reliability, capability are assured 
when choosing Micro-Sci. Pick the drive, pick the 
controller, pick the capacity and function. Whatever 
your need, DOS 3.2, 3.3, Pascal, CP/M, games or 
pre-packaged software, Micro-Sci has the drive. 
Start wherever you choose with the knowledge 
that you can expand without concern. All Micro-Sci 
products are backed by a full 120-day warranty 
(parts and labor). 

Our complete line of Apple compatible products 
makes us the dealer's choice. We're always looking 
for good dealers, 
international dealer inquiries: 
International Markets Co., Telex: 69-6191. 
TELEX CO LSA 



//-SCI 

MICRO-SCI 

17742 IRVINE BOULEVARD • SUITE 205 .TUST1N, CALIFORNIA 92680 • 714/731-9461 -TELEX: 910-346-6739 

MICRO-SCI IS A DIVISION OF STANDUN CONTROLS, INC. 



"APPLE II, APPLE II PLUS ' '"DISK II DAPPLE, APPLE II AND DISK II ARE REGISTERED TRADEMARKS OF APPLE COMPUTERS, CUPERTINO, CALIFORNIA 



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READ (file) read a file into the edit buffer at the current cursor loca- 

tion — implies file insertion, concatenation 

WRITE (file) save the contents of the edit buffer — implies file creation, over- 

writing; if file name is not given, write to current file 

DELETE (object) delete the character to the left, to the right, or at the cursor and 

reformat the screen; for advanced use, object can be a 
character, word, sentence, block, screen, etc. 

SEARCH (object) move the cursor to/past the string "object", which can be de- 

fined explicitly or, for advanced use, defined using metasymbols 

Cursor movement move by character, or, for advanced use, by word, sentence, 

(scroll) block, screen, etc.; moving the cursor past the edges of the 

screen can imply vertical/horizontal scrolling 

QUIT terminate the edit session; prompt for confirmation if changes 

have not been saved (abandoning changes may be intended) 

Table 1: These basic editing commands form a logical and symmetrical set of com- 
monly used functions. Character insertion is always permitted. Note that the read 
and write functions imply file creation and deletion functions that an operating sys- 
tem or the editor must perform automatically. 



Circle 159 on inquiry card. 



commands, divided into a basic 
group and an advanced group. The 
basic commands, which by definition 
are used most often, must be the 
easiest to signal. Some other signaling 
mechanism can be used for more 
esoteric functions. 

The command hierarchy of the 
EMACS screen editor is an interesting 
attempt to reconcile the need for 
simplicity and logic in commands 
with the power of a large command 
repertoire. EMACS is a general-pur- 
pose tool that runs on a number of 
mainframe systems (a microcomputer 
version, called MINCE, is available 
from Mark of the Unicorn, POB 423, 
Arlington, MA 02174). It was ori- 
ginally developed in 1974 at the 
Massachusetts Institute of Technol- 
ogy by Richard Stallman (see refer- 
ence 10). Since then, many user- 
written extensions have been added 
to the basic package. 

The EMACS hierarchy has four 
levels, using the prefixes CTL (con- 
trol), ESC (Escape), CTL-X (press the 
Control and X keys simultaneously), 
and ESC X (press the Escape key and 
then the X key). The first two prefixes 
are for simple commands; the second 
two are for more advanced com- 
mands. For instance, CTL-B moves 
the cursor back one character, while 
ESC B moves the cursor back one 
word; CTL-D deletes the current 
character, while ESC D deletes the 
preceding word. 

Simple functions are simply named 
and thus simple to remember. CTL-X 



precedes some actions considered too 
important for single keystrokes; the 
sequence CTL-X CTL-C, for instance, 
is required to quit the editor. (Requir- 
ing multiple keystrokes to exit an 
editor is one of the simplest and best 
applications of idiot-proofing I have 
encountered.) 

More powerful functions are called 
by entering ESC X and a string; for 
instance, "ESC X fillon" turns on 
word wrapping. This hierarchy 
allows an unlimited number of editor 
functions at the cost of forcing you to 
learn the hierarchy. EMACS can 
grow in power without compromis- 
ing on the integrity of the fundamen- 
tal command structure. 

Text-editing Commands 

The simple functions thus far 
described would be useful for editing 
any kind of sequential file. Other 
functions are more suited to editing 
text. 

First, consider searching for a char- 
acter string. Two popular display 
mechanisms are display results and 
incremental search. In display-results 
searches, the editor moves the cursor 
to the end of (and perhaps highlights) 
the string being sought only after you 
signal the end of the search string 
with some sort of escape sequence. 
This is the more common mechanism. 

In incremental searching, the editor 
searches as each character of the 
string is entered. In theory, you need 
enter only the minimum string neces- 
sary to locate a desired point. If I 



April 1982 © BYTE Publications Inc 297 



Design Guidelines 

The literature abounds with contradictory guidelines for text-editor design, but the following summaries of various sources 
present widely supported principles for promoting ease of use. 

In designing a system, minimize the need for memorization. Optimize operations— common operations should execute rapid- 
ly. Also, change the display as little as possible. Engineer for errors: design out common ones, provide good error messages, 
allow user actions to be reversed, and ensure data structure integrity. 

Hansen (1971) 

Minimize the need to learn about the system. Provide online help messages for the novice and built-in short cuts for experi- 
enced users. Provide a response for every possible user input. 

Wasserman (1973) 

Keep the system simple and responsive with immediate, unambiguous feedback. The user should initiate all actions and be 
able to quit at any time. The system should be flexible, allowing abbreviations, command files, prompting, and subsetting of the 
command structure. 

Cher it on (1976) 

In the command language, provide a complete and symmetric set of functions as well as convenient and consistent abbrevia- 
tions for commands and command arguments. Simple functions should be simple to do, and in general the language should do 
what a reasonably intelligent user would expect. The system should prompt for confirmation before allowing irreversible actions 
(e.g., deleting files). 

Muchnick (1976) 

Allow browsing through text, and let the user see corrections as they're made. Provide status messages that give evidence of 
the system state. 

Gebhardt and Stellmacher (1978) 

Keep in mind that different users prefer different types of text editors; i.e., sophisticated users prefer a powerful editor, while 
beginners prefer a simple one. Also, different kinds of text require different editing commands (e.g., "forward paragraph" for 
editing text as opposed to "forward procedure" for editing PL/I programs). 

Stallman (1979) 



were searching through a text file for 
the word "there/' I would certainly 
not enter just "th." Using incremental 
searching, though, I could safely try 
it and see if it would suffice; if not, I 
could continue typing characters until 
I got where I wanted. Though incre- 
mental searching is not as useful in 
practice as it sounds, the display algo- 
rithm is useful for highlighting blocks 
(see below). 

Line editors usually have very 
powerful string-search functions that 
use metacharacters (characters used 
to describe or delineate other char- 
acters). The usual convention is to 
use * (caret) for the beginning of a 
line, $ (dollar sign) for the end of a 
line, . (period) for "any character," 
and * (asterisk) for "any number of 
the preceding character." Thus the 
search string ^the.*fox$ is inter- 
preted to specify a line beginning with 
"the," ending with "fox," and having 
any number of arbitrary characters in 
between. Metacharacter searches are 
powerful and precise. Sophisticated 



users find metacharacter searching 
almost indispensable. But searching 
for a metacharacter itself requires 
using an "escape sequence" (pressing 
a series of keys to escape from one 
mode of operation into another), a 
concept beginners find hard to grasp. 
Ease of use compels us to abandon 
metacharacters, however reluctantly. 

One function built around charac- 
ter searching is search-and-replace. 
There are four logical variations: re- 
place once, replace-rc-times, replace 
interactively, and replace globally. In 
interactive search-and-replace you 
should have, at every replacement 
point, the option of replacing, skip- 
ping, or quitting. In practice, all but 
replace-rc-times prove useful and 
should be available. 

Most line editors cannot locate 
strings that span lines. This is a severe 
limitation, often forcing you to enter 
text in some artificial manner (such as 
having every sentence on a separate 
line). A screen editor should not be so 
limited. 



The basic text-editing command set 
should include an interactive routine 
for moving and copying text blocks. 
Three locations are required: the first 
and last characters of the block to be 
operated on and the location the 
block will be moved (or copied) to. 
Ease of use suggests that the routines 
prompt you for this information and 
highlight the text block. 

The Honeywell WP 6 text editor 
provides a powerful mechanism for 
outlining text blocks. You position 
the cursor to the first character of the 
block and press, for instance, the 
Copy function key. The system 
prompts, "Copy What?" in the mes- 
sage area and highlights the character 
at the cursor position. The system 
then enters a single-character search 
mode; you can move the cursor to 
any character by entering that char- 
acter. Entering three spaces advances 
the cursor three words; entering a 
period, carriage return, or page mark 
advances the cursor one sentence, 
paragraph, or page, respectively. The 



298 April 1982 © BYTE Publications Inc 




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BYTE April 1982 299 



quadridirectional keys also work, 
either extending or reducing the 
block. Since the block is highlighted, 
you know exactly what is being 
copied. Once the block is marked, 
you press the Execute key, and the 
system prompts, "Copy it to where?" 
Position the cursor to the character 
before which the block is to be copied 
and press Execute again to complete 
the operation. 

Messages to the User 

System messages are, historically, 
coded as an afterthought. But because 
messages are among the most visible 
aspects of the software they are 
among the most important, especially 
for inexperienced users. Time is well 
invested in good system messages. 

Messages should be polite, not im- 
perious; straight, not funny; neutral, 
not personal. There are good and 
well-known reasons for this state- 
ment. For instance, how many times 
would you endure an error message 
like "YOU BLEW IT, BUD!!!" before 
becoming thoroughly annoyed? 
Human-factors research involved 
with large systems has shown that 
users are uncomfortable with com- 
puters that appear to be too lifelike, 
ordering them around or controlling 
them instead of vice versa. Ben 
Shneiderman (see reference 9) cites 
the Library of Congress database 
computer, which is available for 
public use. The programmers had to 
change prompts like "ENTER NEXT 
COMMAND" to "READY FOR 
NEXT COMMAND" because many 
people felt uncomfortable being 
ordered around by the computer. 

Error messages are often written 
from an internal point of view and 
couched in terms of software inter- 
faces, as if the author were peering 
out at the world from the port of a 
disk drive. Useful messages can only 
be written from the user's point of 
view. Ideally, an error message 
should say what went wrong, what 
has happened as a consequence of the 
error, and how to correct the error. 
For example, infinitely better than 
"HOLD BUFFER OVERFLOW," 
which describes an error in terms of 
an internal software event, is "LINE 



TOO LONG; REJECTED. RE- 
ENTER LINE." The latter succinctly 
tells what the user did wrong, what 
happened, and how to rectify the 
situation. 

Help messages, which program- 
mers would never think of providing 
for themselves, are an important aid 
to using any computer system. 
EMACS provides an elaborate, table- 
driven help system that provides a 
one-line description of what each 
keystroke does, a multiline help mes- 
sage for the same command, or a 
summary of related topics gathered 
through substring retrieval. Much is 
possible on a microcomputer system 
as well. Wordstar boasts an im- 
pressive online help facility with four 
levels of detail. Everyone from an ex- 
perienced user to a rank amateur can 
obtain an appropriate level of assis- 
tance. It also has a HELP function, 
which describes the use of each key. 

One grace note that seldom ap- 
pears is the "in progress" message, 
which notifies you that some function 
is underway. EMACS, for instance, 
uses the messages "Reading. . . ," 
"Read," "Writing. . . ," and "Writ- 
ten" for the common I/O commands. 
I always include such messages in the 
command files I write; the system on 
which I work is subject to great fluc- 
tuations in load, and users tell me it's 
comforting to know their jobs haven't 
"curled up and died." 

Multilingual Editors 

Word-processing editors are spe- 
cialized to the needs of editing English 
language text; they word-wrap lines 
and recognize constructs such as 
words, sentences, and paragraphs. A 
more generalized editing tool would 
be more useful to, say, Pascal pro- 
grammers if it could format Pascal 
programs, balance parentheses (move 
the cursor between one parenthesis 
and its corresponding partner), 
recognize constructs such as proce- 
dures, and insert comment lines in the 
proper format. One can imagine the 
utility of an editor that recognizes 
PL/I, BASIC, FORTRAN, COBOL, 
LISP, etc. In fact, EMACS does this, 
making it a general-purpose tool and 
not just a word-processing editor. 



Conclusion 

Software designers make many deci- 
sions about how their software will 
behave. There are several reasons for 
choosing one form of behavior over 
another, based on established human- 
factors principles. An inefficient 
editor with a smooth user interface 
will be better received, and ultimately 
more useful, than an efficient editor 
with an ill-planned user interface. In 
the long run, software should be de- 
signed — and selected — not on the 
basis of what is most machine-effi- 
cient, but on the basis of how well 
people can use it. ■ 



References 

1 . Boies, S. J. "User behavior on an interac- 
tive computer system." IBM Systems 
Journal, Vol. 13, No. 1, 1974, pp. 2-18. 

2.Cheriton, David R. "Man-Machine Inter- 
face Design for Timesharing Systems." 
Proceedings of the ACM National Con- 
ference, 1976, pp. 362-380. 

3.DECsystem 10 TECO Text Editor and Cor- 
rector Program Programmer's Reference 
Manual. (Version 23 of TECO) Maynard, 
MA: Digital Equipment Corp., 1972. 

4.Gebhardt, F., and Stellmacher, I. "Design 
Criteria for Documentation Retrieval 
Languages." Journal of the American 
Society for Information Science, Vol. 29, 
No. 4, July 1978, pp. 191-199. 

5. Hansen, Wilfred J. "User Engineering 
Principles for Interactive Systems." 
AFIPS Conference Proceedings, Vol. 39, 
Fall Joint Computer Conference. Mont- 
vale NJ: AFIPS Press, 1971, pp. 523-532. 

6.Kernighan, Brian W., and P. J. Plauger. 
Software Tools. Reading, MA: Addison- 
Wesley, 1976. 

7. Martin, James. Design of Man-Computer 
Dialogues. Englewood Cliffs, NJ: Prentice- 
Hall, 1973. 

8.Muchnick, Steve S. "The Command Inter- 
preter and Command Language Design of 
the Corn-Share Commander II System." 
Proceedings of the ACM National Con- 
ference, 1976, pp. 367-379. 

9. Shneiderman, Ben. Software Psychology. 
Cambridge, MA: Winthrop Publishers, 
1980. 
lO.Stallman, Richard M. "EMACS: The Exten- 
sible, Customizable, Self-Documenting 
Display Editor." A.I. Memo No. 519. Cam- 
bridge, MA: Massachusetts Institute of 
Technology, June 22, 1979. 
H.Wasserman, Anthony I. "The Design of 
'Idiot-Proof Interactive Systems." AFIPS 
Conference Proceedings, Vol. 42, Pro- 
ceedings of the National Computer Con- 
ference. Montvale, NJ: AFIPS Press, 1973, 
pp. M34-M38. 



300 April 1982 © BYTE Publications Inc 



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BYTE April 1982 301 



Managing Words 

What Capabilities Should You 
Have with a Text Editor? 

The ideal text editor is defined, drawing 
on the experience of many users. 



Craig A. Finseth 

Mark of the Unicorn Inc. 

POB 423 

Arlington, MA 02174 



When moving from a typewriter to 
a computer-based text editor, you 
will encounter a bewildering array of 
new capabilities — some worth more 
than others. This article will single 
out the useful features (i.e., those 
capabilities that make a text editor 
more powerful or easier to use) from ' 
mere gadgetry. Although many of the 
features described here are often 
overlooked at first, they will be ap- 
preciated long after the first thrill of a 
new machine has worn off. 

When you move from a typewriter 
to a text editor, expect to spend some 
time learning the new capabilities 
available to you. Among text-editor 
manufacturers, the temptation to cut 
the learning period short at the ex- 
pense of providing more sophisti- 
cated editing capabilities is ever pre- 
sent. By simplifying, the manufac- 
turer can demonstrate and teach peo- 
ple how to use all of the capabilities in 
a few minutes. Unfortunately, after 
these first few minutes there is no 
more to learn and no easier way of 
doing editing than by the few, simple 
operations that have been taught. As 
a rule of thumb, anything as easy to 



learn as a typewriter is as useful as a 
typewriter. 

The following is a list of features 
desirable in a text editor. Not all fea- 
tures, however, will be useful to 
everyone. If you're planning to buy a 
text editor, you might want to check 

Study the features of a 

text editor carefully 

before you decide to 

buy it. 

the list carefully, noting which fea- 
tures would serve your purposes best. 

Screen Editor: The editor should be 
a screen editor. This means that the 
video display is used as a "window" 
onto the file, showing its current 
state. Thus, you are quickly given 
feedback about what your text looks 
like. You can then immediately see 
where something needs to be 
changed. 

A screen-oriented editor usually 
uses some sort of cursor to indicate 
the active editing point. In general, 
the cursor must be moved to the text 
that is to be changed before any 



changes can be made. There are 
(usually) a number of commands that 
move the cursor to different points in 
the text. For example, one command 
will place the cursor at the end of a 
line, another will place it at the begin- 
ning of a paragraph, and so on de- 
pending on the capabilities of a given 
unit. 

Backup Copy: A good editor 
allows you to edit a copy of the file 
and not the file itself, thus creating an 
implicit backup copy to which you 
can return if you accidentally destroy 
the file. Yet this backup copy will not 
clutter up precious space on your 
disks. 

A good editor will let you read in a 
file and write it out to several other 
files, perhaps after making minor 
changes, without exiting the editor. 
This capability is much easier to pro- 
vide (and thus more common) in 
editors that edit a copy of the file. 

Large Files: A good editor will be 
able to handle very large files 
smoothly and elegantly. When the 
file that is being edited becomes too 
large to fit in memory, parts of it 
should be stored on disk until needed. 



302 April 1982 © BYTE Publications Inc 





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However — and this is most impor- 
tant — none of the internal "breaking 
into pieces" should be visible to the 
user. Specifically, you should not 
have to manually break your file up 
into pieces, nor should there be com- 
mands to "edit the next section of the 
file." You should always be able to 
edit any part of your file on demand 
and never be in a position where 
backing up before a certain point in 
the file is impossible. 

Multiple Buffers and Windows: 
When using a typewriter, you can 
easily switch back and forth between 
tasks, or you can look at several 
documents at once. You don't want 
to give up these abilities when you 
move to a computer. Thus, an editor 
should have multiple buffers and 
multiple windows. 

Multiple buffers store each docu- 
ment separately and allow you to 
switch back and forth between them 
at will. Any changes that have been 
made to any of the documents will 
still be there, intact, if you should 



switch away from a buffer and then 
back again. 

An editor with multiple windows 
will "split" your video screen so that 
you can look at parts of two or more 
documents at the same time (or two 
parts of the same document). With 
this ability, you can make changes in 
one file based on what you are read- 
ing in another one. 

Speed: The editor should be fast 
enough so that it doesn't slow you 
down. This means that it should scan 
the keyboard often enough to retain 
all the characters that have been 
typed and that there should be little 
or no delay between a command and 
its execution. Response time is most 
important on the frequently executed 
commands, such as those that move 
you around in the file or window, 
and less important on the infrequent- 
ly used ones, such as those that read 
or write files. 

If two commands are entered 
quickly, or a second one is entered 
while the editor is updating the screen 



after executing the first, it is more ef- 
ficient if the screen update is aborted 
and the next command executed im- 
mediately. Thus, executing sixteen 
"next-screen" commands in quick 
succession will show the sixteenth 
screen of text only, not all fifteen in 
between. Note that on some operat- 
ing system/hardware configurations, 
it is not possible to detect the second 
or later commands, so this feature is 
not always available. 

Large Screen: The video-terminal 
screen should be as large as possible. 
A standard screen has 24 lines and 80 
columns. An 80-column display is 
usually wide enough for text, but 24 
lines represents only about a third of 
a sheet of paper. This small size can 
produce a feeling of "blindness" in 
users because their attention is 
focused on such a small part of the 
text. Unfortunately, 24 lines is by far 
the most common size. However, 
larger screens do exist: for example, 
the Ann Arbor Ambassador terminal 
will display up to 60 lines at once 




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Part one (FMS-81) gives you the 
essential file and reporting features. 
You can quickly create programs 
with input questions a clerk can 
understand, and with reports a man- 
ager can use. 

And FMS-81 with its new manual, 
is so easy to use, you'll be generating 
reports the first day. FMS-81 sells 
for $495. 

Part two (FMS-82) has all the 
fancy stuff. Including an Extended 
File Maintenance language that lets 
you perform virtually unlimited 
manipulation on up to 19 different 
data files simultaneously. 



Using FMS-82, you or your com- 
puter dealer can make FMS-80 do 
just about anything. FMS-82 sells 
for $495. 

Naturally, FMS-82 is fully com- 
patible with all the files and func- 
tions you generate with FMS-81. 

FMS-81 is so useful, it might 
seem like you'll never need FMS-82. 

But as you expand your use 
of computers, isn't it nice to know 
it's there? 

The FMS family runs under 
CP/M, MP/M, CDOS, and Turbodos. 
Call or write today for a brochure 
detailing the extensive capabilities 
of the Two Door Data Base Manager, 
and the name of your nearest dealer. 

You'll be impressed. 




Plus, Inc 



1120 San Antonio Road 
Palo Alto, CA 94303 
(415) 969-7047 



Q OyV product 

DJR Associates, Inc. 
2 Highland Lane 
North Tarrytown, 
NY 10591 



Circle 400 on inquiry card. 



FMS-80, FMS-81, FMS-82 

TM DJR Associates 
CP/M, MP/M TM Digital Research 
CDOS TM Cromemco 
Turbodos TM Software 2000, Inc. 



Circle 217 on inquiry card. 



(almost a full sheet of paper). 

Due to the 24-line size of most 
screens, it is important that the editor 
devote as much of the screen as possi- 
ble to displaying text and minimize 
the space devoted to unchanging 
status displays. A video terminal is 
very good at displaying things that 
change, and that capability should be 
used to advantage by a text editor. 

Physical Keyboard Characteristics: 
The physical characteristics of a key- 
board are important, too. First and 
foremost, the keyboard and screen 
should be in separate cases (common- 
ly called a "detachable keyboard"). 
By separating the two, the keyboard 
can be adjusted to fit the user, instead 
of forcing the user to adapt to the 
keyboard. This capability is impor- 
tant if you are using the terminal 
eight hours a day. 

A keyboard should have a com- 
fortable, solid feel and should not 
miss or double type characters (i.e., if 
you type "forty," it should not send a 
"orty," "f forty," or "fgorty"). In addi- 
tion, the Shift and Control keys 
should work smoothly with the rest 
of the keyboard so that you indeed 
get a "Forty" and not a "forty," 
"FOrty," or "fOrty." Finally, there 
should be no sharp edges or other 
nuisances to annoy you. The basic 
question is "Will I be comfortable 
typing my next ten million characters 
on this keyboard?" (Ten million 
characters is about a year's worth of 
typing and editing.) 

Keyboard Setup: The editor should 
be set up for use by touch-typists. If 
you cannot touch-type, the specific 
arrangement will make little dif- 
ference to you. If you can touch-type, 
you should look for an editor with a 
set of commands that will rarely re- 
quire your fingers to leave the "home 
position" (the A,S,D,F,J,K,L, and 
semicolon keys). 

Unfortunately for touch-typists, 
special-function keys (usually located 
above the number keys or to the right 
of the basic keyboard) are inefficient. 
It can take one or two seconds to 
move a hand off to one side and back 
again. This amount of time is unac- 
ceptably long for a touch-typist, who 
can easily type ten characters within 
that time. 



Unfortunately for beginners, it 
takes somewhat longer to learn to use 
an editor that has all of its commands 
on the "basic keyboard" than it takes 
to learn an editor with rows of keys, 
each carefully labeled with its use. On 
the other hand, after three weeks, the 
typist will be able to use the basic- 
keyboard editor much more quickly 
than the special-key editor, and the 
extra learning time will be paid back 
many times over. (Just think how 
much longer those ten million charac- 
ters would take to type if you had to 
move your hands around to type 
them.) 

Mnemonic Commands: Regarding 
basic-keyboard editors, there are two 
schools of thought. One school holds 
that commands should be mnemoni- 
cally bound (e.g., ForwardCharacter 
is on F, BackwardCharacter is on B, 
NextLine is on N, and PreviousLine is 
on P). The other school holds that 
commands should be positionally 
bound (e.g., ForwardCharacter on D, 
BackwardCharacter on S, NextLine 
on X, and PreviousLine on E — a 
glance at the keyboard will verify 
that these are indeed arranged in 
some sort of order). 

The arguments for and against 
these systems are similar to the argu- 
ments about function keys. The posi- 
tionally arranged commands are 
quicker to learn for a nontypist. 
However, the mnemonically ar- 
ranged commands are easier to learn 
for a typist (who never looks at the 
keyboard and must stop and think for 
a while to realize that the E key is, in- 
deed, above the S and D keys). In ad- 
dition, the mnemonically arranged 
commands tend to be more evenly 
spaced around the keyboard. Thus, 
they are typed with both hands and 
can be typed quickly. 

Commands Should Match What Is 
Being Edited: The commands given to 
the editor should match the material 
being edited. Everything that is edited 
has characters, lines, and regions (ar- 
bitrary blocks of text) as elements. A 
text file (or document) also has 
words, sentences, and paragraphs. A 
computer program (say, in Pascal) 
has tokens, statements, statement 
groups, and procedures. There 
should be commands to move over 



F2P/F2 

New 8" FD subsystems for CROMEMCO* 
and other general systems 




GENERAL SPECIFICATIONS 

• DRIVE : Ultra, compact NEC FDI165X2 (8"double. 
sided dual -density, direct drive motor), fully com- 
patible with Shugart SA850R 

• ENCLOSURE : 160WX 230Hx5001(mm), power sup- 
ply and noise filter included 

• PRICES : 

&F2P (signal compatible with Persci299) 

$2,580.00 (including FSC-1250) 
&FSC-1250 (1/F for 16FDC & Shugart type drives 

(no modification required of C10S) £550.00 

&F2 (pin compatible with Shugart drives- •$ 1 . 990.00 

SBC-488 

Single-board computer conforming to 
IEEE-488 specifications 




GENERAL SPECIFICATIONS 

• CPU : Z80 • MEMORY : 2716X2732X6116 • I/O : 
6 parallel ports (8255X2), 1 RS-232C port(8251 X 1 ), 
75-19,200 bauds • STANDARD : IEEE-488 1975/ 
1978 (TMS9914) • EXT. BUSS : 8 data lines, 4 ad- 
dress decode outputs, 12 control lines. 

• DIMENSIONS : 210mm Xl20mm ©POWER : 0.8A at 
+5V ©PRICE : $488.00 

GPIB-100 

S-100 multifunction board meeting 
IEEE-488 specifications. 




GENERAL SPECIFICATIONS 

• GPIB : IEEE-488, 1975/1978(TMS9914) 

• TIMER :i00/is to 18 hours (8253) ©INTERRUPT: 
Universal interrupt controller (AM9519) • CLOCK : 
Real time, battery-backup (MSM5832) •BUSS: 
IEEE S-100 • SOFTWARE : All necessary handler 
programs included on 8'diskette • PRICE I $550.00 



^■CROMEMCO is a trade mark of Cromemco Inc. 

ALL PRICES ARE FOB TOKYO AND 
SUBJECT TO CHANGE WITHOUT NOTICE 

(Dealer inquiries invited) 



International Systems & Automation 

ISA co.,ltd. 

HEIAN BLDG. 2-6-16 OKUBO 
SHINJUKU-KU, TOKYO 160 
JAPAN PHONE : 03-232-8570 

TELEX : 2324496 ISATOK, 
CABLE : ISAHEIAN 



April 1982 © BYTE Publications Inc 307 



and to delete any of these units. 

Insert vs. Overwrite: Whether to 
insert or to overwrite characters is yet 
another controversy. To enter text, a 
typed character could overwrite (re- 
place) an existing character. This is 
useful if you are editing a table of 
numbers. Another option would be 
to insert the character between the 
two surrounding characters. (Think 
about proofreaders' marks. There are 
marks to delete and marks to insert, 
but no marks to overwrite text.) 

Consider the basic editing opera- 
tion of replacing one word with 
another completely different one. The 
easiest way to do it is to delete the old 
word and type the new one (inserting 
it, of course). The overwrite way is to 
type the new word. If the new one is 
shorter, the rest of the old one must 
be deleted. If the new one is longer, 
this situation must be noticed in the 
middle of typing it, and you must 
enter some sort of "insert mode" in 
order to finish the word. This is most 
inconvenient for touch-typists, who 
think of words as indivisible objects. 



The ideal editor has available both 
ways of entering text and allows you 
to select between them. However, it 
should be tailored for inserting new 
text, as that is more useful for the 
bulk of editing. 

Control Characters: A good text 
editor should use control characters 
for commands. By using them as 
commands, the "ordinary" characters 
are kept free for what they are most 
useful: text. 

Recovery from Deletions: Assume 
that you have learned the editor well 
and are typing away, giving it move 
and delete commands and merrily in- 
serting text. Suddenly, you realize — 
too late — that you didn't really want 
to delete that sentence. What do you 
do? 

A good editor will have some sort 
of "undelete" operation to bring back 
the last object or objects that were 
deleted, thus saving you from having 
to remember and reenter the deleted 
text. 

State Save: Although you'll prob- 
ably spend most of your time in the 



editor, you occasionally must leave it 
and do something else. However, if 
you are using multiple buffers to ad- 
vantage, it can take quite a while to 
write each buffer to disk and then 
read them all back in again. Thus, an 
editor should have either the ability 
to save what it knows and so pick up 
quickly where it left off (called state 
save) or the ability to temporarily 
escape to the operating system and 
allow you to do some work. The 
crucial point is that you can resume 
editing without having to manually 
reconstruct where you left off. 

Modifiability: Even if an editor has 
all of these features and seems right in 
every way, there are probably ways 
to change it to make using it just a lit- 
tle bit easier. You should be able to 
make modifications in two areas. 

First, you should be able to tailor 
the editor's default values for con- 
trolling parameters such as the right 
margin. By having the editor match 
your tastes immediately, you will 
save quite a bit of time and an- 
noyance by not having to reenter 



What's Good for the Space Shuttle 
is good for your Apple II! . . . 



^ MICROWAR€,> creator of OS-9/BASIC 09 (used by 

N.A.S.A-, and leading Universities, government agencies, 

and corporations Worldwide) joins with STELLATION TWO 

to deliver the same Operating system and Programming 

Language to the APPLE II. 

OS-9/BASIC 09 are the result of a 3 year research project-designed vyith the 6809 
in mind. This "Operators dream machine" combines with THE MILL microprocessor 
board to provide Apple II users with software features previously reserved for Mainframes and mini's. 
JUST PLUG IN THE MILL AND LET BASIC 09 WORK FOR YOU! other Stellation Two products include: 




Spooler: Allows Apple II to print 
Pascal Speedup: THE MILL with 



aatmg Point: Extends the MILL'S po 



ating point number 



MICROWARG, 



The Lobero Building P.O. Box 2342 
Santa Barbara, Ca, 93120 
(805) 966-1140 TELEX 658439 



OS-9 is a trademark of Microware. BASIC09 i 
trademark of Microware and Motorola. 

Apple II »s a trademark of Apple computer'. 



308 April 1982 © BYTE Publications Inc 



Circle 385 on inquiry card. 





No more waiting! 

No more lost time, reduced efficiency, wasted 
dollars. . .waiting for your printer to complete 
a task before you can use your micro. That's 
part of MicroFazer's beauty. But just one part. 
All the proper credentials. Our universal 
parallel in/parallel out data buffer works with 
all popular microcomputers and parallel print- 
ers and plugs in directly to the printer's input 
port. MicroFazer uses standard 64K RAM 
1V1 #^ a 7P-i chips, standard Centron- 

INOW^! Wl til ics s '9 na,s > and draws 
jlm* t^ * power directly from the 

MicroFazer you p^ («*(**> 9 

a_ volt, 300 m A power 

C3H COlXLPUlG supply available where 
i ft p 1 required). All this in 

. a compact package 
3.5 inches by 7 inches 
by 1 inch/Simple. And simply beautiful. 

At a price that won't faze you. Retail 
pricing for 8K model ($1 59) ; 1 6K ($1 89) ; 32K 
($225); and 64K ($299). 

What we promise, we deliver. Micro- 
Fazer isn't somebody^ idea of what an inex- 
pensive printer buffer sh 
available right now for 
delivery. Don't wait 



■'•'" ^.WS\mt 



j J 




■'• '•<•>.■,- 




■ 



For further information and the name of your nearest dealer, call (404) 923-6666 
or fill in this coupon and mail to: Quadram Corporation, 4357 Park Drive, 
Norcross, Georgia 30093. 

Name 



Company. 
Address __ 
City 



. Title . 



.State. 



.Zip. 



Circle 343 on inquiry card. 




Farewell to 
the Florida panther. 







ho one knows how many 
Florida panthers are still 
alive. Perhaps fewer than 
TOO. If these mountain 
lions die, another creature 
will be gone from the earth 
forever . . . the victim, first, 
of predator elimination pro- 
grams, and more recently, 
■:.-.: . . of ever-shrinking habitat. 
But we don't have to bid fare- 
well to the Florida panther. 
'•"The National Wildlife Federation 
*'v has awarded a grant to researchers 
: : . \to study the panther and its future . . . 
arid to draw up a plan for saving it. That's 
just one small example of how the National Wildlife 
Federation is working to save endangered species 
from extinction. Vou can be a part of the effort. ^fil/ 
Join the National Wildlife Federation, Department siQ 
108, 1412 16th Street, NW, Washington, DC 20036. W%k 




3 Great Memory Boards From S.C. Digital 



SlllllllglMimE 



IBilllll lllllllll 



64K DYNAMIC RAM 'Uniselect: 2* 
features: Model 64KUS 

• 16or24bitaddress. • 8bitdata. • Bankselectby 
SW settable port, bits in two blocks. • Two 32kb 
(128kb) addressing. • Transparent refresh - same as 
M:256KE. • Fast access time - 220nsec, will run with 
Z80, Z8000 to 4mhz, 8080, 8085, 8086, 8088 to 5mhz 
without Wait States. • Can be configured to various 
multiusers OS's. • Expandable to 256KB using 41 64's. 




256K DYNAMIC RAM 
features: Model 256KE 

• 16 or