The source code for 86-DOS 1.00, the OS that eventually became MS-DOS and Windows, is now available on GitHub.
Microsoft finally open sources DOS 1.0 - and it's so much more than the code ...
Microsoft’s MS-DOS (and its IBM-branded counterpart, PC DOS) eventually became software juggernauts, powering the vast majority of PCs throughout the ’80s and serving as the underpinnings of Windows ...