Microsoft open-sources “the earliest DOS source code discovered to date”
Summary
Microsoft has released the oldest-known pieces of DOS history, including the 86-DOS 1.00 kernel sources, development snapshots of the PC-DOS 1.00 kernel, and classic utilities like CHKDSK. The materials predate the MS-DOS branding and were painstakingly transcribed from paper printouts by the DOS Disassembly Group, a team led by historians to preserve early code. Microsoft notes that this release sits in the broader context of past open-source efforts for MS-DOS versions and other early projects, all accessible in the same GitHub repo. The story also recounts Tim Paterson’s creation of 86-DOS for Seattle Computer Products, Microsoft’s licensing to IBM, and the evolution toward MS-DOS, with prior rediscoveries and other open-source projects cited for context.