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

In a remarkable move, Microsoft has opened the vault on its computing history by releasing what it describes as 'the earliest DOS source code discovered to date.' This release marks a significant milestone, showcasing the foundational elements of the original MS-DOS operating system that helped establish Microsoft as a leader in consumer computing. This newly unveiled source code predates the MS-DOS branding, offering insights into the early development of operating systems. Included in this release are the sources for the 86-DOS 1.00 kernel, several development snapshots of the PC-DOS 1.00 kernel, and popular utilities like CHKDSK. Microsoft’s own Stacey Haffner and Scott Hanselman shared this exciting news in a joint post. To put this into perspective, the journey of MS-DOS began with programmer Tim Paterson, who initially developed 86-DOS—originally known as QDOS, short for 'quick and dirty operating system'—for an Intel 8086-based computer kit from Seattle Computer Products. As Microsoft sought an operating system for the IBM PC 5150, it licensed 86-DOS and subsequently hired Paterson to further its development, eventually acquiring the rights. This pivotal operating system was then licensed to IBM under the name PC-DOS, while Microsoft maintained the rights to sell it as MS-DOS. The widespread adoption of third-party IBM PC clones during the 1980s and 1990s solidified MS-DOS as the go-to operating system for countless users, making this release not just a nostalgic look back, but a valuable piece of technology history.