That’s no joke. Microsoft and IBM have participating forces Open source code of the MS-DOS 4.0 operating system in 1988 under license MIT License. Why? Well why not?
Like Scott Hanselman, Microsoft’s Vice President of Developer Communities, and Jeff Wilcox, its head Microsoft Open Source Program Officerecounted on Microsoft’s Open Source Blog, “a young British researcher named Connor ‘Star Frost’ Hyde recently corresponded with former Microsoft Chief Technical Officer Ray Ozzie” about the relationship between DOS 4, Multitasking DOS (MT-DOS), and what would become of IBM and Microsoft. Operating system/2.
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That prompted Hanselman and Wilcox to dig deep into Microsoft’s archives. The blog post continues: “While they could not find the full source code for MT-DOS, they did find MS-DOS 4.00, the version we are releasing today, along with the files this additional beta binary, PDF files of documentation, and disk images.”
This is not the first time Microsoft has released MS-DOS source code. Back in 2014, Microsoft open source MS-DOS for versions 1.25 and 2.0 via the Computer History Museum.
Other versions of DOS have also been open sourced over the years. PC-MOS/386, a multi-user MS-DOS clone by Norcross, The Software Link based on GA, is open source in 2017. It runs most standard DOS and 386 protected mode applications.
Indeed, it is a better DOS operating system than MS-DOS 4.0. For those who didn’t run it in 1988 — when The Cosby Show and Roseanne were the most popular TV shows in the United States and Joe Montanna was leading the San Francisco 49ers to their third Super Bowl victory — MS -DOS 4.0 is a terrible operating system.
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Awful? Popular programs of the time — such as WordPerfect 5.1, Lotus 1-2-3 and Doom — always broke that. You’re on a mission and, bang, your program completely crashes. Long before we knew and hated the Windows Blue Screen of Death, MS-DOS 4.0 PC users were terrified.
That’s mainly because MS-DOS 4.0 uses a whopping 92KB of RAM. Nowadays, you won’t notice your watch using that much RAM. But back in the day, when 640K was what you got on high-end PCs, it was a big deal. It used more memory than any version of DOS before or since.
PC users return to MS-DOS 3.3, which I recommended at the time, or switch to it DR-DOS of Digital Research 3.41.
How bad is MS-DOS 4? DR-DOS version numbers have begun to mimic MS-DOS version numbers to suggest that the former will function the same as the latter. But there is no DR-DOS 4.0. Instead, Digital Research named the new 1989 version DR-DOS 5.0 to prevent people from thinking it had any connection to MS-DOS 4.0.
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Indeed, perhaps one reason why so many people were willing to try the new Unix-like operating system, Linux, in 1991 was because MS-DOS 4.0 was so frustrating for so many users.
Today, you can download MS-DOS 4.0 source code and ran it myself on the original IBM PC XT (surely someone still has one running somewhere), the newer Pentium, and with open source PCem And 86 boxes emulator. It can also work with Oracle Virtual Box or an old Linux MS-DOS virtual machine DOSEMUbut I haven’t had a chance to test it yet.
