MS-DOS 4

MS-DOS 4 is a family of versions of MS-DOS, initially released in 1988.

History
Initially, the project was named "MS-DOS 3.40", and under this name was mentioned in the 1988-09 issue of Serbian computer magazine "Svet Kompjutera", as well as in a contract between Microsoft and Zenith Data Systems from August 1987.

MS-DOS 4.00 was released in July 1988, only to be replaced by MS-DOS 4.01 in November 1988 due to a major bug. MS-DOS 4.02 was also mentioned in PX05132, however, if existing, it is yet to be found.