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Encyclopedia > MS DOS
 Starting MS-DOS... C:\>_ 
An example of MS-DOS's command line interface, this one showing that the current directory is the root of drive C

Microsoft's disk operating system, MS-DOS, was Microsoft's implementation of DOS, which was the first popular operating system for the IBM PC, and until recently, was widely used on the PC compatible platform. It was originally released with the PC in 1981 and had seven major versions before Microsoft stopped development in 1995. It was the key product in Microsoft's growth from a programming languages company to a diverse software development firm, providing the company with essential revenue and marketing resources.



MS-DOS was created by computer manufacturer Seattle Computer Products as 86-DOS, commonly known as QDOS (Quick and Dirty Operating System). In a sequence of events that would later inspire much folklore, Microsoft licensed QDOS to IBM on behalf of SCP. Microsoft acquired the system from SCP shortly before the PC's release.


IBM and Microsoft both released versions of DOS. Microsoft released their versions under the name "MS-DOS", while IBM released their versions under the name "PC-DOS", with the following timeline:

  • PC-DOS 1.0 - August, 1981 - Initial release with the first IBM-PC
  • PC-DOS 1.1 - May, 1982
  • MS-DOS 1.25 - May, 1982 - First release for non-IBM hardware
  • MS-DOS 2.0 - March, 1983
  • PC-DOS 2.1 - October, 1983
  • MS-DOS 2.11 - March, 1984
  • MS-DOS 3.0 - August, 1984
  • MS-DOS 3.1 - November, 1984
  • MS-DOS 3.2 - January, 1986
  • PC-DOS 3.3 - April, 1987
  • MS-DOS 3.3 - August, 1987
  • MS-DOS 4.0 - June, 1988
  • PC-DOS 4.0 - July, 1988
  • MS-DOS 4.01 - November, 1988
  • MS-DOS 5.0 - June, 1991
  • MS-DOS 6.0 - March, 1993
  • MS-DOS 6.2 - November, 1993
  • MS-DOS 6.21 - February, 1994
  • PC-DOS 6.3 - April, 1994
  • MS-DOS 6.22 - June, 1994 - Last stand-alone version released
  • PC-DOS 7.0 - April, 1995
  • Windows 95/MS-DOS 7.0 - August, 1995 - First version not released stand-alone
  • Windows 95 OSR2/MS-DOS 7.1 - August, 1996 - Added support for FAT32 file system
  • Windows Me/MS-DOS 8.0 - September 14, 2000 - Final version of MS-DOS

Source: PC Museum (http://members.fortunecity.com/pcmuseum/dos.htm)

MS-DOS grew to include more features from other operating systems. MS-DOS 2.0 introduced features from UNIX such as subdirectories, command input/output redirection, and pipes.

With Intel's introduction of the 80286 microprocessor, IBM and Microsoft began work on a joint project called OS/2, originally a protected-mode version of MS-DOS with a GUI, but Microsoft soon abandoned the project to devote full resources to Windows NT. Digital Research created the GEM environment which reached minimal popularity, but both were soon eclipsed by Microsoft's Windows GUI package, reportedly due to Microsoft's exclusive agreements with computer hardware vendors.

Legal issues

Version 6.0 included the DoubleSpace file system, which provided automatic compression of file data. Stac Technologies successfully sued Microsoft for patent infringement regarding the compression algorithm used in DoubleSpace. Version 6.22 provided a new file system, DriveSpace, that avoided these issues.

Prior to 1995, Microsoft licensed MS-DOS to computer manufacturers under three types of agreement: per-processor (a fee for each system the company sold), per-system (a fee for each system of a particular model), or per-copy (a fee for each copy of MS-DOS installed). The largest manufacturers used the per-processor arrangement, which had the lowest fee. This arrangement made it expensive for the large manufacturers to migrate to any other operating system, such as DR-DOS. In 1994 the US government charged Microsoft with violations of antitrust law, and a settlement agreement limited Microsoft to per-system licensing. Digital Research did not gain by this settlement, and years later its successor in interest Caldera sued Microsoft for damages. This lawsuit was settled with a monetary payment.


MS-DOS was not designed to be a multi-user or multitasking operating system, but many attempts were made to retrofit these capabilities. Many programs were developed using the Terminate and Stay Resident (TSR) technique and other mostly-undocumented functions to provide pop-up applications including Borland's once popular Sidekick product. Add-on environments like DESQView attempted to provide multitasking, and achieved some success when later combined with the memory-management hardware of the Intel 80386 processor.

User interface

MS-DOS employs a command line interface and a batch scripting facility via its command interpreter, command.com. MS-DOS was designed so users could easily substitute a different command line interpreter, for example 4DOS.

MS-DOS compatibility with other Microsoft operating systems

After the release of the Apple Macintosh in 1984, people desired to have a graphical user interface. Many programs running under MS-DOS tried to fill the void by creating their own graphical interface, such as Microsoft Word for DOS, XTree, and the Norton Shell. However, this required duplication of effort and did not provide much consistency in interface design (even between product lines).

Early versions of Microsoft Windows were ordinary programs which ran on top of MS-DOS and its clones. Later versions were launched from DOS but "extended" it by going into protected mode. Still later versions of MS Windows ran independently of DOS but included much of the old code such that DOS could run in virtual machines under the new OS. The latest versions of MS Windows are continually dropping support for legacy MS-DOS code, especially code that attempts to manipulate the hardware directly. Microsoft has a product named Virtual PC that allows MS-DOS to run concurrently with other operating systems on a single computer.

Related systems

Several similar products were produced by other companies. In the case of PC-DOS and DR-DOS, it is common but incorrect to call these "clones". PC-DOS and MS-DOS were (to continue the genetic analogy) "identical twins" that diverged only in adulthood and eventually became quite different products; DR-DOS was a clone of itself once removed.

Under Linux it is possible to run copies of DOS and many of its clones under dosemu, a Linux-native virtual machine for running real mode programs. There are a number of other emulators for running DOS under various versions of UNIX, even on non-x86 platforms.

See also

External links

  • Richard Bonner's DOS website (http://www.chebucto.ns.ca/~ak621/DOS/DOS-Head.html)
  • Batfiles: The DOS batch file programming handbook and tutorial (http://purl.oclc.org/net/Batfiles/)
  • MS-DOS Reference (http://www.nukesoft.co.uk/msdos/)
  • A Brief Timeline of DOS (http://www.acad.humberc.on.ca/~frig8279/osessay/dos/history)
  • Linux/dosemu (http://www.dosemu.org/)
  • Ralf Brown's Interrupt List (http://www-2.cs.cmu.edu/afs/cs/user/ralf/pub/WWW/files.html)



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