Microsoft Releases Historic MS-DOS And Word Source Code To The Public

Microsoft Releases Historic MS-DOS And Word Source Code To The Public

Microsoft, in conjunction with the Computer History Museum in Silicon Valley, has released the source code for MS-DOS 1.1, MS-DOS 2.0, and Word for Windows 1.1a. These programs are probably the three most important releases in the history of Microsoft: MS-DOS would create and secure Microsoft’s monopoly of the PC market for more than 20 years, and the massive success of Word for Windows would go on to cultivate Microsoft’s Office suite, which has generated hundreds of billions of dollars for the company.

Why would you want to check out the source code for MS-DOS or Word for Windows? Well, the primary reason is for educational purposes. It would probably be a bit daunting to peruse the millions of lines of code in a modern operating system — but you could probably learn a lot by taking a look at MS-DOS 1.1, which occupied just 12 kilobytes of RAM. It’s worth pointing out that both MS-DOS 1.1 and 2.0 are written in assembly language (ASM), and the code is quite well documented — so, if you’re doing some assembly work at university, hacking MS-DOS might make for a pretty cool project.

Word processing revenue share – WordPerfect vs. Word for Windows

The code for Word for Windows 1.1a is much more complex — and there’s a lot of it (in C this time, rather than ASM). Again, it might be a fun project to hack the code, and then load it up in a Windows emulator. To be honest, having the code for Word 1.1a is more of a historic curio than anything else — combined with the release of Windows 3.0 in 1990, and the success of the cheap IBM PC clones, Word would go on to capture 50% of the word processing market in just four years. In eight years, Word accounted for more than 90%. The popularity of Windows certainly helped Word decimate the incumbent, WordPerfect — but it was probably more a case of aggressive marketing, and the easy-to-use WYSIWYG interface, that handed Word the crown.

A snippet of code from Word 1.1a’s spelling library

In both cases, the source code is made available for educational and non-commercial purposes only. You can hack away at the code, but you can’t redistribute it. What isn’t clear is if you can look at the MS-DOS code, and then continue to work on a truly open source project like FreeDOS. The Microsoft Research License that MS-DOS is released under is fairly restrictive — but then again, I can’t really see Microsoft chasing people over code that’s 30 years old. (Though, having said that, one of Microsoft’s closely guarded FAT patents has been used to squeeze millions of dollars from Android and Linux licensees…)

For more background info on MS-DOS, check out our 30th birthday post from a couple of years ago, or hit up our Computer History landing page for more historical tidbits. If you want to download the source for MS-DOS or Word, visit the Computer History Museum website. (If you’re ever passing through Mountain View, you should pay the Museum a real visit; it’s amazing.)