Microsoft DOS History(What is, Concept and Definition)

1981	Microsoft licensed the operating system 86-DOS to SCP (Seattle Computer Products) for $ 25,000 on July 27, 1981.
1981
1982	Microsoft PC-DOS 1.1 was released in May 1982, with support for double-sided disks.
1982	MS-DOS 1.25 was released in August 1982.It was the first version titled "MS-DOS".
1983	MS-DOS 2.0 was released in March 1983, designed for IBM PC XT.It introduced support for hard drives.
1983	MS-DOS 2.1 was released in November 1983, designed for IBM PCjr.It introduced support for half-height disk drives and ROM cartridges.
1984	MS-DOS 3.0 was released in August 1984, designed for IBM PC AT.
1985	MS-DOS 3.1 was released in April 1985.Marketed as "MS-DOS for Networks", it was the first version of DOS to support local area networks.
1986	MS-DOS 3.2 was released in April 1986, with support for 3 1/2 inch, 720 KB floppy drives.
1987	MS-DOS 3.3 was released in April 1987, designed for IBM PS/2.It provided support for 3 1/2 inch, 1.44 MB floppy drives and extended (non-primary) disk partitions.
1987	MS-DOS 3.31 was released in November 1987, designed for Compaq computers.Added support for hard disk partitions larger than 32 MB.
1988	MS-DOS 4.0 was released in July 1988, with multitasking.It was mainly used in Europe, and is sometimes referred to as European MS-DOS 4.0 .
1988	MS-DOS 4.01 was released in November 1988, introducing support for volume serial numbers.Unlike MS-DOS 4.0, version 4.01 did not support multi-tasking.
1991	MS-DOS 5.0 was released in June 1991.It featured support for 3.5-inch, 2.88-MB floppy disks, and a full-screen text editor, "edit." It was the first version of MS-DOS which included himem.sys, which loaded part of the operating system into the UMA.
1993	MS-DOS 6.0 was released in August 1993.It featured a QBASIC help system, disk compression (through the DBLSPACE utility), UMA optimization, and MSAV antivirus software.
1993	MS-DOS 6.2 was released in November 1993 and featured critical bug fixes for DBLSPACE and SCANDISK, a replacement for the CHKDSK utility.
1994	MS-DOS 6.21 was released in March 1994.It removed the DBLSPACE utility, which legally violated third-party disk compression software STACKER.
1994	MS-DOS 6.22 was released in April 1994.It included DRVSPACE, a compression utility that replaced DBLSPACE.It was the last standalone version of MS-DOS to be released.
1995	Windows 95 was released on August 24, 1995.On the Windows 95 command line, the operating system version number was listed as MS-DOS version 7.0.