Back in 2014, Microsoft open sourced MS-DOS as part of a collaboration with the Computer History Museum. Last week, Microsoft has re-open-sourced MS-DOS on GitHub. The new repo contains the original source-code and compiled binaries for MS-DOS 1.25 and MS-DOS 2.0. Microsoft is making this move so that MS-DOS source code will be easier to find, reference-to in external writing and works, and to allow exploration and experimentation for those interested in early operating systems. Microsoft also highlighted some interesting things about MS-DOS.

1. All the source for MS-DOS 1.25 and 2.0 was written in 8086 assembly code
2. The source code for the initial release of 86-DOS dates from around December 29th 1980
3. The MS-DOS 1.25 code dates from around May 9th 1983, and is comprised of just 7 source files, including the original MS-DOS Command-Line shell – COMMAND.ASM!
4. MS-DOS 2.0 dates from around August 3rd 1983, and grew considerably in sophistication (and team size), and is comprised of 100 .ASM files
5. There are some interesting documentation (.TXT, .DOC) files interspersed with the source and object files – many are well worth a read, as are many of the source code comments!

Check out the GitHub repo here.

Source: Microsoft via: ZDNet