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History of DOS

MS-DOS began as QDOS (for Quick and Dirty Operating System), written by Tim Paterson for computer manufacturer Seattle Computer Products (SCP) in 1980.
It was marketed by SCP as 86-DOS because it was designed to run on the Intel 8086 processor.
QDOS function calls were based on the dominant CP/M-80 operating system, written by Digital Research, but it used a different file system.
In a sequence of events that would later inspire much folklore, Microsoft negotiated a license for QDOS from SCP in December 1980 for $25,000, then re-licensed QDOS to IBM. Microsoft then acquired all rights to QDOS for only $50,000 from SCP in July, 1981, shortly before the PC’s release.
The original MS-DOS advertisement in 1981.
IBM and Microsoft both released versions of DOS;
The IBM version was supplied with the IBM PC and known as PC-DOS.
Microsoft released its versions under the name “MS-DOS”.
Computer advertisements of this period often claimed that computers were “IBM-Compatible” or very rarely “MS-DOS compatible.” The two terms were not synonyms. There were computers which used MS-DOS which could not run all the software that an IBM-Compatible machine could.
An example is the Pivot, which used MS-DOS but was not IBM-Compatible.
The versions of MS-DOS and PC DOS and their releases are the following:
• PC DOS 1.0 – August 1981 – initial release with the first IBM-PC (COMMAND.COM is 4959 bytes)
• PC DOS 1.1 – May 1982 – support for 320 be double-sided floppy disk
• MS-DOS 1.25 – May 1982 – first release for IBM PC compatibles marketed under different brands (COMMAND.COM is 4986 bytes)
• MS-DOS 2.0 – March 1983 – introduced subdirectories, handle-based file operations, command input/output redirection, and pipes. Microsoft decided to use backslashes as pathname separators rather than slashes as on Unix apparently due to the latter character being used as the switch character in most DOS and CP/M programs. Adds support for hard drives and 360KB floppy disks
• PC DOS 2.1 – October 1983 – support for IBM Paccar
• MS-DOS 2.11 – March 1984 – non-English language and date format support (COMMAND.COM is 16229 bytes)
• MS-DOS 2.25 – October 1985 – better support for Japanese Kanji, and Korean character sets, shipped to western Pacific countries only
• MS-DOS 3.0 – August 1984 – added support for PC AT: 1.2 MB floppy disks and hard disk partitions of up to 32MB, one primary and one “logical drive” in an “extended partition”
• MS-DOS 3.1 – November 1984 – support for Microsoft networking
• MS-DOS 3.2 – January 1986 – support for 3.5 inch, 720 kB floppy disk drives (v 3.21 COMMAND.COM is 23612 bytes)
• PC DOS 3.3 – April 1987 – support for IBM PS/2: 1.44 MB floppy disk drives, added codepage support (international character sets) (COMMAND.COM is 25307 bytes)
• MS-DOS 3.3 – August 1987 – supported multiple logical drives (COMMAND.COM is 25276 bytes)
• MS-DOS 4.0 – June 1988 – derived from IBM’s codebase rather than Microsoft’s
• PC DOS 4.0 – July 1988 – added DOS Shell & support for hard disks of >32MB using the format from Compaq DOS 3.31. But it had many bugs and less free conventional memory than before. Generally regarded as an unpopular release
• MS-DOS 4.01 – December 1988 – bug-fix release (COMMAND.COM is 37557 bytes)
• MS-DOS 5.0 – June 1991 – memory management, full-screen editor, QBasic programming language, online help, and DOS Shell gains task switcher. Also add file transfer facility licensed from Rupp Technology (Fast Lynx) (COMMAND.COM is 47845 bytes)
• MS-DOS 6.0 – March 1993 – added DoubleSpace disk compression, disk defragmentation, and other features (COMMAND.COM is 52925 bytes)
• MS-DOS 6.2 – November 1993 – bug fix release (COMMAND.COM is 54619 bytes)
• MS-DOS 6.21 – February, 1994 – following Stac Electronics lawsuit, removed DoubleSpace disk compression (COMMAND.COM is 54619 bytes)
• PC DOS 6.3 – April 1994
• MS-DOS 6.22 – June 1994 – last official stand-alone version. DoubleSpace replaced with non-infringing but compatible DriveSpace tool (COMMAND.COM is 54645 bytes)
• PC DOS 7.0 – April, 1995 – bundles Stacker in place of DriveSpace
• MS-DOS 7.0 – August 1995 – shipped embedded in Windows 95. Included Logical block addressing and Long File Name (LFN) support
• MS-DOS 7.1 – August 1996 – shipped embedded in Windows 95B (OSR2) (and Windows 98 in June 1998). Added support for FAT32 file system
• MS-DOS 8.0 – September 2000 – shipped embedded in Windows Me. Last version of MS-DOS. Removes SYS command, ability to boot to command line and other features
• PC DOS 2000 – year 2000-compliant version with minor additional features. Final member of the MS-DOS family

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