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Rich Cini

2 articles First covered May 3, 2026, latest May 25, 2026

A scan of the 86-DOS changelist from Tim Paterson's 1981 assembler printout, the kind of artifact Microsoft released under MIT on April 28.

Microsoft just open-sourced 86-DOS. Tim Paterson's 45-year-old listings are now on GitHub under MIT.

Yufeng Gao and Rich Cini scanned Tim Paterson's 1981 assembler printouts. Microsoft pushed them to DOS-History/Paterson-Listings on April 28, the 45th anniversary.

A page of the original 86-DOS 1.00 assembler listing showing handwritten changelist annotations

Open Source·last month

Microsoft open-sourced the earliest known DOS code, transcribed from a stack of Tim Paterson's printouts.

MIT-licensed at GitHub on April 28, the 86-DOS 1.00 kernel and PC-DOS development snapshots were OCR'd from 45-year-old assembler listings.