Appendix B: Versions of DOS
This is the version released with the IBM PC
computer in August 1981. The program had 4,000 lines of
code and reguired 136K bytes of storage when fully
Versions 1.1 and 1.25
Version 1.1 was released in May 1982 for PC
computers with two disk drives and to enable writing on
both sides of the diskette. This doubled the diskette
capacity from 160K to 320K bytes. Microsoft released MS
DOS Version 1.25 for IBM compatible computers.
Was released in March 1983 for the IBM PC XT
computer. Initially IBM only wanted an upgrade to
accommodate a hard disk on the new PC XT computer.
However Paul Allen decided to enhance the software and
add additional features. Some of those new features were
hierarchical directories, a limited form of multitasking
for printing and certain UNIX features . The floppy disk
format was also changed from 8 sectors per track to 9
sectors that increased the storage capacity to 360 K
bytes. The program now had 20,000 lines of code.
Version 2.1 (PC-DOS)
Was introduced in November 1983 for the IBM PC
Was released in March 1984 for international
customers. It supported the variations in date format
and comma instead of a period for decimal point
notation. The program was translated into many languages
and sold worldwide. By June 1984, Microsoft had licensed
MS-DOS to 200 manufacturers.
AB/2 A History of the Personal Computer
Was released in August 198 4 for the IBM PC AT
computer. It accommodated high-density 1.2 megabyte
diskettes. It also added features such as: RAM disk,
volume names and the ATTRIB command. The program now
consisted of 40,000 lines of code.
Was released in March 1985 to add networking
capabilities for IBM PC Network and Microsoft MS-Net.
Was released in December 1985 to accommodate 3 1/2
inch disk drives.
Was released in April 1987 to accommodate multiple
partitions, improved foreign character support, support
for a 32 megabyte hard disk and the IBM PS/2 series of
Was released in June 1988. It had a graphical user
interface or DOS shell for use with a mouse, EMS support
and support for hard disk partitions over 32 megabytes.
The program required 1.1 MB of storage.
Was released in June 1991. It featured a MS-DOS
kernel which loaded into HMA (high memory), 80386 memory
management, a new shell, improved multitasking
capabilities, limited switching capabilities, on-line
help and a full-screen editor.
Was released in March 1993. The new features added
were: DoubleSpace disk compression, improved memory
management, backup and defrag utilities licensed from
Appendix B: Versions of DOS AB/3
Symantec Corporation, anti-virus and undelete utilities
licensed from Central Point Software Inc., Multi-
configuration support on start-up, an improved
SmartDrive, three new commands (Move, Deltree and
Choice) and a file transfer utility called Interlink.
The program required 8.4 MB of storage.
Was released in November 1993. DoubleGuard that is
a part of DoubleSpace is added to verify data integrity
before writing to disk.
Versions 6.21 and 6.22
Version 6.21 was released in February 1994 to
delete DoubleSpace after litigation with Stac
Electronics. Version 6.22 was released in June 1994 to
add a new disk compression program called DriveSpace.
MS-DOS was essentially made obsolete with the
introduction of Microsoft Windows 95 in August 1995.
Windows 95 integrates the functionality of MS-DOS and
the previous Windows graphical interface.