Microsoft has now shared the source code of 86-DOS 1.00 through an open-source repository on GitHub, coinciding with the 45th anniversary of this operating system developed by Tim Paterson. This version served as the basis for licensing to IBM, evolving into PC-DOS and eventually MS-DOS.
In a blog post on Microsoft Open Source, the company details the early evolution of MS-DOS, emphasizing that such disclosures aim to allow access to important historical software for education, archiving, and general interest. Earlier, Microsoft had made public the code for MS-DOS versions 1.25, 2.0, and 4.0.
Beyond just the GitHub repository, preserving software heritage involves more than digital files; it encompasses digitized printouts, company records, assembly language outputs, and tangible relics from the operating system creation process during the late 1970s and early 1980s. The initial blog post on the Windows Command Line site about releasing MS-DOS 1.25 and 2.0 sources highlights the importance of surrounding context to comprehend the origins of modern systems.
This assortment of materials represents a valuable resource for computing history experts: A group of dedicated researchers and archivists, including Yufeng Gao and Rich Cini, has gathered, digitized, and converted various DOS-period source documents originally from Tim Paterson, the creator of DOS.
Among the contents are the 86-DOS 1.00 kernel sources, multiple early builds of the PC-DOS 1.00 kernel, and familiar tools like CHKDSK. These include not only assembly code printouts but also those for the assembler tool itself, providing uncommon glimpses into the origins of MS-DOS and PC-DOS, as well as the practices of operating system creation in that era, distinct from later interpretations.
The announcement overlooks the fact that Bill Gates did not single-handedly create MS-DOS 1.00. In 1980, facing a pressing need for a reliable OS for the IBM PC, Gates acquired 86-DOS—also called QDOS—from Seattle Computer Products and its founder Tim Paterson for roughly $75,000. Following modifications by Gates, PC-DOS 1.0 launched in August 1981.
Microsoft kept ownership of the DOS rights and adapted it for sale as MS-DOS on non-IBM compatible machines, setting the stage for the company's dominance in the personal computer industry. Additional details appear in the Windows history overview.
Further reading: Methods for executing classic DOS programs on Windows 11
The piece first appeared in our affiliated outlet PC-WELT, adapted and translated from its German version.
Hans-Christian Dirscherl started his career in computing with files like Autoexec.bat and config.sys, programming in Turbo Pascal and C, and systems such as Sinix and WordPerfect. Over nearly 25 years, he has covered a broad spectrum of technology subjects, from current events to product evaluations and purchase recommendations.