‘Clean-room reimplementation’ of DR-DOS hits early beta, modernizing the operating system 38 years after its debut — runs Doom, Warcraft, SimCity, and other period-appropriate titles

DR DOS version 9.0 is now in beta testing, with Revision 291 recently released and available for anyone to download and test. Developer and Redditor CheeseWeezel announced the publicly available milestone as a “complete clean-room reimplementation of DR-DOS from scratch.” The OS is in development mostly to provide DOS enthusiasts and retrocomputing hobbyists “real DR DOS, legally unencumbered.”

Digital Research Inc’s DOS, or just DR DOS for short, was originally developed by legendary computing figure Gary Kildall, probably even more famous as the creator of CP/M. It quickly gained a reputation for its technical superiority to rival DOS platforms, supporting more advanced features earlier, offering superior efficiency, and broader compatibility. But of course, as you know, Microsoft managed to dominate the DOS market thanks to canny/lucky business moves, like its IBM PC bundling. Its success would be sealed by being the default PC platform development target, plus a ladleful of market inertia.

DR DOS has changed hands quite a few times since its 1988 debut. It was sold to Novell in 1991, which brought it up to version 7.0. Caldera took the reins in 1996, followed by DeviceLogics in 2002. Since 2022, it has been in the hands of Whitehorn Ltd. Co., and that is where it is now being reimplemented.

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Four years or so later, the “process of clean-room re-implementing this historically significant operating system” has been deemed advanced enough for the public. DR DOS version 9.0 hit beta this year, and Revision 291 was recently released as per the linked Reddit thread.

A mission statement of sorts on the official site, dr-dos.com, says that the OS has been “built from scratch to honor Kildall's vision while creating a modern, legally unencumbered DOS for the next generation of enthusiasts, developers, and hackers.” As it stands, it includes a comprehensive set of commands and a useful set of utilities, plus some hacker-friendly memory manipulation commands, as standard.

Regular beta updates are now promised. The site includes a basic roadmap, of sorts, which says that newer releases are going to include FAT32 filesystem support, additional drive letter support, enhanced batch scripting features (FOR loops, SET command), and more.

The current release of DR DOS already works quite well, with complex apps and games. Specifically, games like “Doom, Warcraft, SimCity, Stronghold, Commander Keen, Oregon Trail, and plenty of other period-accurate titles” are claimed to run. However, downloaders are warned that there are “rough edges,” and the OS should not be installed on a device which is storing important data. Perhaps install it on a spare machine or disk, or in a VM environment, for testing.

I confess to having a soft spot for Digital Research for developing GEM (the Graphics Environment Manager), which was used to provide a GUI on some PCs before Windows matured. GEM is probably best known as the native Atari ST GUI, though.

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