Microsoft finally open sources DOS 1.0 - and it's so much more than the code

Microsoft has open-sourced PC-DOS 1.00, the very first operating system shipped on IBM's original PC back in August 1981 — a program Microsoft bought for under $100,000 and turned into a decades-long empire. Released under the permissive MIT license on GitHub, the code includes hand-written notes from original developer Tim Paterson, offering rare insight into how early operating system development actually worked, not just the final polished result.