MSDOS History: MSDOS was distributed by Microsoft starting in 1981. It was based initially on a CPM-like OS written by Tim Patterson called QDOS (later, Seattle DOS). The following are the formal version releases. They do not include OEM versions of MSDOS of which there were several.

1.0 -- 1981 -- Supported 8088 CPUs using 160K single sided floppy disks. Only the 7 bit ASCII character set was built into the OS although the eighth bit in the byte was carried along and displayed/saved/etc.

1.25 -- 1982 -- Supported floppy drives with heads on both sides of the disk. MSDOS 1.0 required modifying the disk by cutting a second locator notch and manually flipping the floppy disk to get to the second 160K. Supported non-IBM hardware.

2.0 -- 1983 -- added support for 360K floppies and 10mb hard drive. Incorporated optional file-handle based file IO. Added IO redirection and piping.

2.11 -- 1983 -- support for 8 bit characters (i.e. for languages using characters with values 128-255)

3.0 -- 1984 -- support for 1.2MB floppies and hard drives to 32MB

3.1 -- 1984 -- allowed "drive letters" to reference external (network) storage (Network Redirector)

3.2 -- 1986 -- allowed an extended disk partition up to 32MB in addition to the primary partition. 720K floppy support

3.3 -- 1987 -- PS/2 support. 1.44MB Floppies. Code Pages. Multiple disk partitions.

4.0 -- 1988 -- FAT16 (disks to 2.14GB). Extended Memory support. Code Pages (alternate national character sets). Graphical User Shell. The release had annoying bugs and excessive memory footprint.

4.1 -- 1988 -- Bug fixes (lots of them)

5.0 -- 1990 -- Many more bug fixes. High/Upper Memory Support. 2.88MB Floppies. Disk caching. Disk file undelete. EDIT replaced EDLIN

5.0a -- 1991/2 -- Bug fixes for CHKDSK/UNDELETE

6.0 -- 1993 -- Disk Compression. Anti-Virus and Backup utilities. MOVE command. Graphical Shell shipped separately.

6.2 -- 1993 -- Compression bug fixes. Upgrades to disk handling -- SCANDISK, DISKCOPY, Smartdrive

6.21 -- 1993 -- Disk Compression temporarily removed because of legal issues

6.22 -- 1994 -- Disk Compression returned with a slightly altered name (DRVSPACE vs DBLSPACE).

7.0 -- 1995 -- Released as part of Windows 95. Long File Name Support. Some utilities (e.g. UNDELETE) removed.

7.1 -- 1997 -- Released with Windows 95 OSR2. Support for FAT32.

8.0 -- 2000 -- Released with Windows Me. Removes support for SYS command and other features removed in Windows Me.

There are/have been several MSDOS clones and extensions -- Freedos, QDOS(ndos), DRDOS, 4DOS, OpenDOS, PCDOS. OS/2 and Windows NT/2000/XP support and sometimes expand upon most MSDOS capabilities.

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