MS-DOS 4.0

In a significant move for tech enthusiasts and historians alike, Microsoft has made the source code for MS-DOS 4.0 publicly available.

This decision marks a pivotal moment in the accessibility of historical software, allowing developers, students, and technology aficionados to explore the inner workings of one of the most influential operating systems in the history of personal computing.

Microsoft provided the source code for MS-DOS versions 1.25 and 2.0 to the Computer History Museum ten years ago., which was later republished for reference. This operating system’s 8086 assembly code, written over 45 years ago, is remarkable.

“Today, IBM and we are releasing MS-DOS 4.00’s source code under the MIT license in the spirit of open innovation. MS worked with IBM for parts of DOS 4.0 and created Multitasking DOS, which was never widely released,” Microsoft said.

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Background on MS-DOS

Microsoft Disk Operating System, commonly known as MS-DOS, was the dominant operating system for personal computers compatible with IBM PCs during the 1980s and early 1990s.

Initially developed in 1981, MS-DOS was critical in the personal computing revolution. It provided a command line interface for users to execute programs and manage files.

MS-DOS 4.0

On April 25, 2024, Microsoft took a step towards preserving and sharing technological history by archiving and releasing the source code of MS-DOS 4.0 on its official GitHub repository.

This version of MS-DOS includes various enhancements and features not present in its predecessors and is now available for public access in a read-only format.

MS-DOS 4.0, initially released in the late 1980s, introduced several improvements over earlier versions:

  • Graphical User Interface: Although primarily a text-based interface, MS-DOS 4.0 included a simple graphical menu system, making it more user-friendly.
  • Improved Memory Management: It supported larger memory sizes, which was a significant step forward at the time.
  • Enhanced Disk Utilities: The version included advanced disk management tools, improving the efficiency of data storage and retrieval.

Significance of the Release

The release of the MS-DOS 4.0 source code is more than just a nostalgic gesture; it serves multiple educational and practical purposes:

  • Educational Value: Students and new programmers can study the source code to gain insights into the early development of operating systems.
  • Historical Importance: It preserves a crucial piece of computer history, providing researchers and historians with material to study the evolution of software development.
  • Community Engagement: Tech enthusiasts can explore the code, potentially finding ways to repurpose or integrate old software into new technologies.

How to Access the MS-DOS 4.0 Source Code

The source code for MS-DOS 4.0 is available on Microsoft’s GitHub repository. Since the repository has been archived, it is read-only, meaning no new changes or contributions can be made.

However, users can still download, study, and use the code for personal or educational purposes. Here’s how you can access it:

  1. Visit the GitHub page: Microsoft MS-DOS
  2. Navigate to the MS-DOS 4.0 directory.
  3. Download the files you are interested in.

Microsoft’s decision to release the MS-DOS 4.0 source code is a commendable step towards open-source contributions and preserving digital history. By making this pivotal technology available to the public, Microsoft honors its legacy and enriches the global computing community.

Whether you’re a developer, student, or curious, the MS-DOS 4.0 source code offers a unique glimpse into the software that once powered millions of computers worldwide.

Suppose you’d like to run this software yourself and explore it. In that case, Microsoft has successfully run it directly on an original IBM PC XT, a newer Pentium, and within the open source PCem and 86box emulators Microsoft added.

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BALAJI is an Ex-Security Researcher (Threat Research Labs) at Comodo Cybersecurity. Editor-in-Chief & Co-Founder - Cyber Security News & GBHackers On Security.