⚙️ Microsoft has released what it calls the earliest discovered DOS source code, extending prior releases that included MS-DOS 1.25 and 2.11 in 2018 and MS-DOS 4.0 in early 2024. The company published scanned listings, internal memos, assembly printouts and other analog artifacts from the late 1970s and early 1980s, and it included digitized paper archives to preserve development context.

A team of IT historians led by Yufeng Gao and Rich Cini located, scanned and transcribed original printouts from Tim Paterson, the developer of DOS. The archive documents the development of PC-DOS 1.00, the first DOS release for the IBM PC, and includes the 86-DOS 1.00 kernel, intermediate PC-DOS 1.00 builds, utilities such as CHKDSK and the assembler.

Many pages contain Paterson’s handwritten annotations, and the originals will reside at the Interim Computer Museum. The files appear on GitHub in the DOS-History/Paterson-Listings repository under the MIT license.