Microsoft Open Sources Its Decades-Old MS-DOS 1.25 and 2.0


While we were all ready for the Windows 10 October 2018 update, Microsoft gave us a little 90’s feel. The MS-DOS 1.25 and 2.0 source code is finally public after over 3 decades. Rich Turner, the Redmond software creator, took the time to remind us about the old times. Notably, Tim Paterson, the original author of the code, found the original source code of MS-DOS 1.25 and the six-inch thick assembly print out stack back in 2014. Microsoft then handed the 1.25 and 2.0 to Computer History Museum.

Turned uploaded the code on GitHub to make it easier for MS-DOS admirers to get it. Though the code is open source now, he would still appreciate if the original source remains unmodified. The binaries are as small as 12 kilobytes. It can give you a power of manipulating disks and launch or close applications through a text-based command shell running full-screen.

The source code is quite readable as compared to the enormous assembly code. Rich Turned, who is a Senior Program Manager in Microsoft in said that, “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.”

The original 86-DOS came way back in December 1980. Turner penned MS-DOS 1.25 code around May 1983 and then the MS-DOS 2.0 in August 1983. Here are some interesting facts about the code shared by Microsoft:

  • The exact dates of 86-DOS, MS-DOS 1.25, and MS-DOS 2.0 are 29 December 1980, 9 May 1983, and 3 August 1983 respectively.
  • MS-DOS comprises only 7 source files, which also includes COMMAND.ASM- the original MS-DOS command-line shell.
  • MS-DOS 2.0 eventually became bigger and sophisticated. It was packed with exactly 100.ASM files. MS-DOS 2.0 turned out to be a milestone for Microsoft because it started supporting IBM XT floppy disks and it clones of 180 and 360 kilobytes. It also started supporting 32MB hard drives before MS-DOS 3.0 rolled out.

You can check out more interesting source code information in the documentation available in.TXT and.DOC format along with source and object files. We have witnessed some inconsistency in the available files. More interestingly, it’s great to see that even if the development language has transformed in the last 35 years, some developers have hated writing history and comments throughout.

We at AppsToFollow are yet to get the start and make source files. However, when we went through the revision history and comments, it takes you on a tour of simpler times when things were simple codes and a computer was not meant for everyone, unlike the present era.