After original author Tim Paterson found the source for MS-DOS 1.25 (along with a six-inch stack of assembly print-outs), Microsoft handed the code for 1.25 and 2.0 to the Computer History Museum back in 2014.
Turner has now uploaded the code to GitHub to make it easier to find, although he'd really like it if you didn't suggest modifications to the hand-crafted assembly.
The v1.25 code is utterly fascinating and consists of only seven assembly source files. The binaries will fit into 12 kilobytes of memory and gave users a full-screen text-based command shell in which to manipulate disks or fire up applications.Kids, if you want to know what a kilobyte is, go ask your parents. It's kind of like a Terabyte byt way, way more compact.