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Microsoft’s historic MS-DOS has a prominent place in the development of the personal computer. It was a leading operating system for x86 during the 1980s and 1990s before Microsoft ceased development in 2000. Not just that, MS-DOS was a driving force behind Microsoft’s growth into the leading PC software vendor.

Back in March 2014, Redmond released MS-DOS 1.25 and 2.0 source code to the Computer History Museum. For years later, the company now wants the platform to be more widely available. With that in mind, Microsoft has released MS-DOS on GitHub.

In an announcement post, the company says it is re-open-sourcing the operating system. Of course, Microsoft is in the process of finalizing a $7.5 billion acquisition of GitHub. Now, MS-DOS is available to anyone who wants to use it. The GitHub repository for the OS can be downloaded here.

“The source files are being (re)published for historical reference purposes and to allow exploration and experimentation for those interested in early PC Operating Systems. The source will be kept static, so please don’t send Pull Requests suggesting any modifications to the source files!

Microsoft says the reason for the release is to give users easier access to MS-DOS source files. Certainly, GitHub provides a more efficient read and refer experience to the original compressed archive file.

Interesting Information

Also in the announcement, Microsoft pointed to some interesting facts about the OS. For example, the source code dates from December 29th 1980:

  • All the source for MS-DOS 1.25 and 2.0 was written in 8086 assembly code
  • The source code for the initial release of 86-DOS dates from around December 29th 1980
  • 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 – ASM!
  • 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
  • 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!