45 years later, earliest DOS source code transcribed from a stack of old printouts found in a garage — code was open-sourced to mark 86-DOS 1.00’s anniversary
The earliest source code for 86-DOS 1.00 has been transcribed from old printouts found in Tim Paterson's garage and released on GitHub to mark the operating system's 45th anniversary. Microsoft VP Scott Hanselman confirmed the transcribed code is accurate and recompiles to match the original binaries exactly. The release includes kernel code, utilities, and the Microsoft BASIC-86 Compiler runtime library, offering insight into early OS development.
- ▪The source code for 86-DOS 1.00 was recovered from dot matrix printouts stored in Tim Paterson's garage.
- ▪Microsoft verified that the transcribed code recompiles byte for byte to the original binaries.
- ▪The release includes PC-DOS 1.00 pre-release kernels, utilities like CHKDSK, and the Microsoft BASIC-86 Compiler runtime library.
- ▪Scans of the original printouts with handwritten notes are available via the Internet Archive.
- ▪Microsoft has previously open-sourced other versions of MS-DOS, including versions 1.25, 2.11, and 4.00.
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Software Operating Systems 45 years later, earliest DOS source code transcribed from a stack of old printouts found in a garage — code was open-sourced to mark 86-DOS 1.00’s anniversary News By Mark Tyson published 2 May 2026 Microsoft VP confirms transcribed document “is perfect and recompiles byte for byte to the original binaries.” When you purchase through links on our site, we may earn an affiliate commission. Here’s how it works. (Image credit: Microsoft, Tim Paterson at the Internet Archive) Copy link Facebook X Whatsapp Reddit Pinterest Flipboard Email Share this article 0 Join the conversation Follow us Add us as a preferred source on Google Newsletter Subscribe to our newsletter Microsoft continues to make some of the earliest chapters of its operating system history open-source…
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