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Appendix B: Versions of DOS 

Version 1.0 

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. 

Version 2. 

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 
Junior . 

Version 2.11 

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 

Version 3. 

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. 

Version 3.1 

Was released in March 1985 to add networking 
capabilities for IBM PC Network and Microsoft MS-Net. 

Version 3.2 

Was released in December 1985 to accommodate 3 1/2 
inch disk drives. 

Version 3.3 

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 
computers . 

Version 4.0 

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. 

Version 5.0 

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. 

Version 6.0 

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. 

Version 6.2 

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.