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

Microsoft released the earliest known DOS source code materials on the 45th anniversary of 86-DOS 1.00, including source listings for the 86-DOS 1.00 kernel, PC-DOS 1.00 development snapshots, and utilities like CHKDSK. The materials were transcribed from assembler printouts on continuous paper that were preserved by original DOS developer Tim Paterson. These releases aim to make historically important systems software available for study, preservation, and research.

Source: Ars Technica | 2026-04-30