Microsoft open sources MS-DOS 4.0

More open source surprises for you today, coming from Microsoft too which is always interesting to see as they've now open sourced MS-DOS 4.0.

Added into their existing MS-DOS repository on GitHub which already had MS-DOS v1.25 and v2.0, they've now expanded it to include MS-DOS v4.0 which was jointly developed by IBM and Microsoft. This is all available under the permissive MIT license.

From the repo:

The MS-DOS v1.25 and v2.0 files were originally shared at the Computer History Museum on March 25th, 2014 and are being (re)published in this repo to make them easier to find, reference-to in external writing and works, and to allow exploration and experimentation for those interested in early PC Operating Systems.

They're doing this for "historical reference and will be kept static" so they're not accepting pull requests, but that doesn't stop someone forking them and doing pretty much whatever they want now it's all under the MIT license. Great news for preservation.

It will be interesting to see if they eventually keep going adding in more later versions, and perhaps even get some earlier versions of Windows up too. Now that would truly be something don't you think?

There's a fun little tidbit of history in the Microsoft blog post on it with the code being found on some old floppy disks.