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Microsoft released part of the history of open-source computing this week: the company partnered with IBM to publish the source code for 1988’s MS-DOS 4. 00, an edition known more for its unpopularity, bugs, and complicated history of progression than for its usefulness as open software. Source Software. Computer operating system.
The MS-DOS 4. 00 code is available on Microsoft’s MS-DOS GitHub page with versions 1. 25 and 2. 0, which Microsoft released in cooperation with the Computer History Museum in 2014. All open source versions of DOS have been released as MS-DOS 4. 00. MIT License.
Initially, MS-DOS 4. 00 would come with new multitasking features that allowed the software to run in the background. This edition of DOS, also known as “MT-DOS” or “MS-DOS multitasking” to distinguish it from other editions, has only been released through a few European PC brands and never as a standalone retail product.
The source code Microsoft released this week is not intended for this multitasking edition of DOS 4. 00, and Microsoft’s Open Source Programs Office was “unable to locate the complete source code” for MT-DOS in its search. Instead, Microsoft and IBM published the source. code for an absolutely separate edition of DOS 4. 00, evolved primarily through IBM to add more capability to the existing non-multitasking DOS edition that ran on most IBM PCs and PC clones of the time.
Microsoft never reverted to its concept of DOS multitasking in later versions. Multitasking would take advantage of the capabilities of graphical operating systems such as Windows and OS/2, while MS-DOS versions 5. x and 6. x continued the old one by one. Time style from previous versions.
Microsoft has released documentation and binaries for MT-DOS and “may update this edition if more are discovered. “The company thanks English researcher Connor “Starfrost” Hyde for disclosing all of this source code as part of an ongoing review of MT-DOS. which it documents on its website. Hyde posted screenshots of a 1984 edition of MT-DOS, adding the “session manager” he used to track and transfer between running applications.
The public release of MS-DOS 4. 00 is less known for its new features than for its maximum memory usage; DOS 4. 00 can consume up to 92 KB of RAM, much more than the roughly 56 KB used until MS-DOS 3. 31, and the minor update 4. 01 reduced this figure to about 86 KB. Later versions of MS-DOS 5. 0 and 6. 0 reached their maximum limit. with 72 or 73 KB, and even IBM’s DOS 2000 PC only needed about 64 KB.
These RAM numbers would be rounding errors in any modern computer, but in the days when RAM was expensive, computers maxed out at 640 KB, and virtual memory didn’t exist, such a buildup on the computer required a big problem. Today’s modern computer enthusiasts still tend to forget about MS-DOS 4. 00 and recommend the 3. 31 edition for its lower memory usage or later editions for its extensive feature set.
Microsoft has opened up other legacy code over the years, adding older versions of MS-DOS, Word for Windows 1. 1a, GW-BASIC from 1983, and the original Windows registry manager. Although most of them were released in their original form without any updates or changes, the Windows File Manager is actively maintained. First, it was tweaked enough to run natively on modern 64-bit and Arm PCs running Windows 10 and 11, but it was updated with new fixes and features recently. as of March 2024.
The release of MS-DOS 4. 00 is rarely the only new feature DOS historians have had their hands on this year. One of the earliest known editions of 86-DOS, the software that Microsoft would buy and turn into an operational formula for the original. IBM PC, discovered and uploaded to the Internet Archive in January. A first edition of Microsoft’s discontinued OS/2 edition was also discovered in March.
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