Multitasking "MS-DOS Version 4.00"
Released in 1985 by Microsoft
For IBM PC and compatibles

This is the multitasking version of MS-DOS that Microsoft originally
planned to release as MS-DOS 4. It was a parallel project to DOS,
never released to the regular consumer market, and Microsoft
backtracked to base its next consumer release off of DOS 3.3.

This archive contains two 360k disk images that have been slightly
modified.

Note that although it calls itself "MS-DOS Version 4.00", it is a
different product than the MS-DOS 4 that actually shipped.

Source: http://jsmachines.net.
