Apr 30, 2024 10:39:00

Microsoft makes MS-DOS 4.0 open source

MS-DOS 4.0 , released by Microsoft in 1986, was open sourced and released on GitHub on April 25, 2024 local time.

Open sourcing MS-DOS 4.0 - Microsoft Open Source Blog
https://cloudblogs.microsoft.com/opensource/2024/04/25/open-sourcing-ms-dos-4-0/

Microsoft released the source code for MS-DOS versions 1.25 and 2.0 through the Computer History Museum in March 2014. This was also intended as a historical document summarizing 'how MS-DOS was born.'

Microsoft subsequently re-open-sourced versions 1.25 and 2.0 of MS-DOS, making the source code available on GitHub.

Open source MS-DOS source code released on GitHub - GIGAZINE

By Jeff Dlouhy

Following this effort, Microsoft partnered with IBM to release the MS-DOS 4.0 source code on GitHub under the MIT license in a spirit of open innovation.

GitHub - microsoft/MS-DOS: The original sources of MS-DOS 1.25, 2.0, and 4.0 for reference purposes
https://github.com/microsoft/MS-DOS

'MS-DOS 4.0 has a somewhat complicated and interesting history behind it,' wrote Scott Hanselman, Microsoft's vice president of development communities, and Jeff Wilcox, director of the Open Source Program Office. 'Microsoft partnered with IBM on some of the code, but at the same time they also created a branch of DOS called Multitasking DOS, which was never widely released.'

The reason Microsoft decided to open source MS-DOS 4.0 in the first place was because a young British software researcher, Conor Hyde, was corresponding with Ray Ozzie, former Chief Technology Officer (CTO) of Microsoft, about the retro software he had collected. In Hyde's collection, Ozzie discovered an unreleased beta binary of MS-DOS 4.0 that had been created while he was working at Lotus Notes. Hyde was working on documenting the relationship between MS-DOS 4.0, MT-DOS, OS/2 , etc., so he contacted Microsoft's Open Source Program Office about the unreleased beta binary of MS-DOS 4.0 that he had discovered.

Although some versions of MS-DOS 4.0, MT-DOS, OS/2, etc. are available on the Internet, the ones found in Hyde's collection were unreleased and have never been made public. Therefore, Microsoft's Hanselman, with the help of Internet archivist Jeff Sponaugle, is attempting to image the original MT-DOS 4.0 disk.

Although Microsoft's Open Source Program Office was unable to find the complete source code for MT-DOS in the Microsoft archives, they were able to find the source code for MS-DOS 4.0, which was released as open source, along with additional beta binaries and PDFs. This made the open source release possible.

As mentioned above, each version of MS-DOS is historical, so it is available on GitHub as read-only, but anyone can fork the repository and experiment with it.