Microsoft open-sources "the earliest DOS source code discovered to date"
Microsoft has released the earliest discovered source code of DOS, predating the MS-DOS branding. This release includes the 86-DOS 1.00 kernel and various development snapshots. The code was painstakingly transcribed from paper printouts by a dedicated team of historians and preservationists.
- ▪Microsoft has open-sourced the earliest DOS source code discovered to date.
- ▪The release includes the 86-DOS 1.00 kernel and development snapshots of PC-DOS 1.00.
- ▪The source code was transcribed from paper printouts, as it had not been stored digitally.
Opening excerpt (first ~120 words) tap to expand
now that’s dedication Microsoft open-sources “the earliest DOS source code discovered to date” Old 86-DOS source code dates back to the time before Microsoft bought it. Andrew Cunningham – Apr 30, 2026 10:20 am | 110 An IBM PC sitting next to old printed-out 86-DOS source code. Credit: Rich Cini An IBM PC sitting next to old printed-out 86-DOS source code. Credit: Rich Cini Text settings Story text Size Small Standard Large Width * Standard Wide Links Standard Orange * Subscribers only Learn more Minimize to nav Several times in the last couple of decades, Microsoft has released source code for the original MS-DOS operating system that kicked off its decades-long dominance of consumer PCs.
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Excerpt limited to ~120 words for fair-use compliance. The full article is at Ars Technica.
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