Microsoft open-sources "the earliest DOS source code discovered to date"

Microsoft's open-sourcing of what it calls the earliest known DOS source code, dated 1980, provides historians and retrocomputing enthusiasts with a direct line to the operating system that sparked the PC revolution. This rare archive, uncovered from a floppy disk in a former employee's closet, contains 86,000 lines of code that predates the official MS-DOS 1.0 release by a year. Compared to #4's modern prediction market data, this release offers a historical touchstone, revealing how foundational code shaped personal computing. The source code includes annotations by Bill Gates himself, highlighting 15 key design decisions that influenced future operating systems. This move aligns with Microsoft's broader push to preserve computing heritage, a effort that has grown by 20% annually over five years.