Back in 2014, Microsoft released the MS-DOS source code (versions 1.25 and 2.0) via the Computer History Museum. Last week, Microsoft “re-open-sourced” MS-DOS, but this time around via its GitHub acquisition.
Microsoft officials said they opted to put MS-DOS on GitHub because ” it’s much easier to find, read, and refer to MS-DOS source files if they’re in a GitHub repo than in the original downloadable compressed archive file,” in the words of Senior Program Manager Rich Turner, who also has been spearheading Microsoft’s Windows Subsystem for Linux and console work.
To be clear, the source files are for reference and internal experimentation only. Microsoft isn’t allowing pull requests and modifications to the source.
The source code for the initial release of 86-DOS dates from around December 1980, Turner noted, and the MS-DOS 1.25 code from around May 1983. MS-DOS 2.0 dates from around August 1983.
The Register has a quick romp with some of the twists and turns in the history of MS-DOS, for those who might want a refresher.