Microsoft open-sourced MS-DOS 4.0.

[chants]

3.3 is already on the web, though likely someone here hasn't learned to search so lmgtfy:

https://linuxreviews.org/42.9_GB_Of_Microsoft_Source_Code_Leaked:_Historicans_Can_Now_Study_The_Source_Code_For_MS-Dos_3.3_To_Windows_XP

V7.1 is the good one but AFAIK the Windows 95 source never leaked with this version? XP and 2000 are too late

[Eleven]

Originally Posted by chants

3.3 is already on the web...

I remember reading through the old leaked source code years ago and checking the MS-DOS 4.0 code release I'm glad they left all the swearing in the comments and names:

invoke	path_search			; find the mother (result in execpath)
or	AX, AX				; did we find anything?
je	badcomj45			; null means no (sob)
cmp	AX, 04H 			; 04H and 08H are .exe and .com
jl	rsrch_br1			; fuckin' sixteen-bit machine ought
jmp	execute 			; to be able to handle a SIXTEEN-BIT
rsrch_br1:				; DISPLACEMENT!!