A Blast from the Past: Microsoft Releases MS-DOS 4.0 Source Code on GitHub

In a bold move, Microsoft has decided to release the source code for its iconic MS-DOS 4.0 operating system on GitHub, making it available for public scrutiny and modification. This nostalgic gesture marks the 45th anniversary of the original release, which dates back to 1975. The software giant has taken a significant step towards embracing open-source principles by giving developers access to this historic codebase.

For those who may not be familiar, MS-DOS (Microsoft Disk Operating System) was the dominant force in the early days of personal computing, powering IBM-compatible PCs and other systems during the 1980s and 1990s. The operating system’s popularity was immense, with over 100 million users worldwide at its peak. Its influence is still felt today, as many modern operating systems, including Windows, owe a debt to MS-DOS’ innovative architecture.

The source code release comprises approximately 25,000 lines of C and assembly language code, which has been carefully preserved and curated by Microsoft’s archives team. This move paves the way for developers to explore, learn from, and potentially contribute to the original MS-DOS 4.0 framework. The availability of this historic codebase will undoubtedly spark interest among retro-computing enthusiasts, software historians, and those seeking a deeper understanding of the operating system’s inner workings.

The release is significant not only as a testament to Microsoft’s commitment to open-source values but also as a nod to its roots in the early days of computing. It serves as a reminder that even the most influential technologies have humble beginnings and are built upon the shoulders of innovative pioneers. This act of transparency allows developers to appreciate the evolution of operating systems, fostering a sense of community and collaboration.

I’d rate this release 4.5/5 stars, with only minor deductions for the lack of modernized documentation and explanations for beginners. The sheer volume of code may overwhelm some users, but enthusiasts will relish the opportunity to delve into MS-DOS’ inner workings. With GitHub as the platform, contributors can easily submit pull requests, report issues, and collaborate on improvements.

In conclusion, Microsoft’s decision to release MS-DOS 4.0 source code is a remarkable step towards embracing open-source principles and preserving computing history. This gesture will undoubtedly spark new interest in retro-computing and inspire future generations of developers to learn from the past while shaping the future of operating systems. I recommend giving it a try if you’re interested in exploring the roots of modern computing.


* Unparalleled access to historic codebase
* Opportunity for learning and exploration
* Potential contributions from the community


* Limited documentation for beginners
* Large amount of code may be overwhelming for some users

Overall, this release is a fantastic example of Microsoft’s willingness to share its legacy with the world, allowing developers to learn from the past and shape the future. I’m excited to see how the community will engage with this treasure trove of retro-technology.

Rating: 4.5/5 stars


* For retro-computing enthusiasts and historians
* Developers interested in learning about MS-DOS’ architecture
* Those seeking a unique challenge or insight into computing history

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