Summary
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Microsoft has released the source code for 86-DOS 1.00, including its kernel, PC-DOS snapshots, and utilities.
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Includes handwritten notes from 86-DOS creator Tim Paterson with timelines, feature context, and errors.
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The release highlights the history of the PC and the origins of MS-DOS; the artifacts will be on display at the Temporary Computer Museum.
To mark the operating system’s 45th anniversary, Microsoft released the source code for 86-DOS 1.00, the first version of DOS released for the IBM PC. The tech giant says a dedicated team of historians and curators located, digitized and transcribed the DOS-era source list from Tim Paterson (pictured below), the original creator of DOS.
This list includes the 86-DOS 1.00 kernel, development snapshots of the PC-DOS 1.00 kernel, and a few utilities you might recognize, like CHKDSK, providing a rare glimpse into how DOS was created back in the day.
Additionally, the lists go even further and include handwritten notes created by Paterson, offering more context around the development of DOS, whether it’s a timeline of changes, when features were implemented, or even errors and other issues. All of these artifacts will be on display at the Interim Computer Museum and were donated by Paterson.
The release of 86-DOS 1.00 offers a fascinating look at the history of the PC
The operating system laid the foundation for Microsoft’s future
In 1980, Microsoft was given the opportunity to create the operating system for IBM’s PC, and then CEO Bill Gates was tasked with delivering it on short notice. Naturally, rather than developing an operating system from scratch, Gates purchased 86-DOS, also known as QDOS, from Seattle Computer Products and its creator, Tim Paterson, for around $75,000, making Microsoft the tech giant it is today.
At the time, the operating system ran on 160 KB floppy disks and did not support hard drives, but it eventually became the basis for what would become MS-DOS, the dominant PC operating system of the 1980s and early 1990s. Previously, the first available versions of MS-DOS were 1.25 and 2.0.
“These releases are intended to make historically significant system software available for study, preservation, and simple curiosity,” write Microsoft’s Stacey Haffner, director of Microsoft OSPO and developer advocate, and Scott Hanselman, vice president and member of the Microsoft/GitHub technical staff.
In 2018, Microsoft (re)open sourced MS‑DOS 1.25 and 2.11, and in 2024, the company made the source of MS-DOS 4.0 public.
You can find Paterson’s DOS listings, including the 86-DOS 1.00 kernel source code, here.
Microsoft just created its own code from open source from the 70s, and you can download it right now
A look into Microsoft’s past.