MS-DOS 6

MS-DOS 6 is a family of versions of MS-DOS, initially released in 1993.

MS-DOS 6.00
MS-DOS 6.00 was released in 1993. This version included many new utilities and features:
 * Disk defragmenter
 * Disk compression
 * Anti-virus
 * A new backup system
 * PC-PC file transfer tools

It was heavily criticized as buggy by the media, primarily due to file corruption issues with DoubleSpace (disk compression utility based on Vertisoft's DoubleDisk) and the lack of tools to repair such issues.

MS-DOS 6.20
MS-DOS 6.20 was released in November 1993. Microsoft skipped the 6.10 version number as a marketing response to IBM PC-DOS 6.10, which was released at the same timeframe. After complaints from users about data loss, DoubleSpace was finalized. The  program has been added, and   and   have been improved.

MS-DOS 6.21
MS-DOS 6.21 was released in March 1994 specifically to remove DoubleSpace due to legal injunction by Stac Electronics over the use of Stacker code in DoubleSpace; during the interim period, the replacement software, DriveSpace was not yet ready.

MS-DOS 6.22
MS-DOS 6.22 was generally available in June 1994, three months after 6.21. MS-DOS 6.22 shipped with "Enhanced Tools", including a disk compression tool known as DriveSpace, which was free from Stacker code. An included supplemental disk also ships with copies of tools dropped from the previous version of MS-DOS.