Before “Micro Soft” became Microsoft, Bill Gates wrote BASIC interpreters. The first operating system Microsoft released was a Unix distribution called Xenix. Then, in 1980, Microsoft had its big break: IBM needed an operating system for its programmable IBM PC and asked Gates if he could deliver it. The rest is history.
Now, Microsoft released the source code and notes for PC-DOS 1.00, the first DOS version for the IBM PC.
Microsoft buys 86-DOS for $100.000
In the real world, Gates and company needed to create an operating system as quickly as possible. But they didn't have the time to develop their own, so they bought 86-DOS, also known as QDOS, from Seattle Computer Products and its inventor, Tim Patterson, for just under $100.000. Yes, it was a steal! DOS would become the program that would set Microsoft on the path to becoming one of the leading companies in the technology industry for the next 50 years and beyond.
To date, the first DOS sources that were widely accessible to developers were MS‑DOS 1.25 and 2.0, which Microsoft initially released via the Computer History Museum in 2014 and then republished them on GitHub in 2018. These GitHub releases, along with the more recent publication of the Microsoft-IBM MS‑DOS 4.00 shared sources, showed that Microsoft was increasingly comfortable treating its once-proprietary DOS code as an educational and historical resource.
When Microsoft and the Computer History Museum first released early MS-DOS source code in 2014, it was under a tightly restricted license that allowed only “non-commercial research, experimentation, and educational purposes” and explicitly prohibited reuse in other projects. This approach made the code readable but not truly usable. The subsequent re-release of MS-DOS 1.25 and 2.0 on GitHub under the MIT License changed this, adopting a more permissive license that the Free Software Foundation describes as GPL-compatible and allowing for almost unlimited reuse, modification, and redistribution.
Putting DOS 1.0 under the same license completes the story from the beginning of the PC era. Instead of being locked away in a file, the code is now a navigable Git tree. With this code, system programmers, educators, and retrocomputing enthusiasts can clone, build, and experiment using modern toolchains.
It's not just DOS source code that Microsoft is sharing. Microsoft said: "These materials are not simply operating system releases in the traditional sense. In many cases, the entries represent working states at specific points in time and handwritten notes, maintained by Tim Paterson himself. Think of them as a printed commit history of a Git repository."
Although the press releases will range from very select to rare, I said I'd pass...because sometimes the editors hide.
