In cooperation with the excellent Computer History Museum in Mountain View, Microsoft released the source code to MS-DOS 1.1, MS-DOS 2.0, and Microsoft Word for Windows 1.1a.
Here’s hoping that this is a sign of things to come and Microsoft will also release the source code to historic versions of Windows 1.x, 2.x and 3.x, further versions of MS-DOS—and maybe even OS/2 1.0!
The poor CHM server is currently suffering from a severe overload so actually looking at the goodies will have to wait…
Later: Yes, it’s the real thing. There’s the MS-DOS source code, and even more—someone left in a few WordStar overlay files. Somehow I doubt Microsoft is legally allowed to redistribute files with “COPYRIGHT (C) 1982, MICROPRO INTERNATIONAL” in them… oh well.
The DOS 1.1 source code seems to be a somewhat random collection of files saved by Tim Paterson, as used by SCP.
The 2.0 source code appears to have been taken from a MS-DOS 2.0 OAK… which means no useful IO.SYS source code. On the other hand, there is a smattering of documentation.
All in all, fun stuff!