Microsoft finally open sources DOS 1.0 - and it's so much more than the code

Microsoft has open-sourced DOS 1.0, its very first operating system. This release provides valuable historical insight into the early days of personal computing. The open-source code allows developers and enthusiasts to explore and learn from the origins of PC software.

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PublishedTuesday, April 28, 2026 at 8:45 PMApr 28, 08:45 PM

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Want a blast from the past? Microsoft just open-sourced its very first operating system, offering a rare insight into the PC's earliest days.

Before "Micro Soft" became Microsoft, Bill Gates wrote BASIC interpreters. Microsoft's first shipping operating system was a Unix distro called Xenix. Then, in 1980, Microsoft got its shot at the big time: IBM needed an operating system for its planned IBM PC and asked Gates if he could deliver one. You betcha! The rest is history.

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Microsoft finally open sources DOS 1.0 - and it's so much more than the code

Original article excerpt