Through the 1980s and 1990s, the PC world seemed destined to revolve forever around Microsoft. And yet there was one operating system that, for a while, was technically better than MS-DOS and came surprisingly close to rewriting the history of personal computing. That system was DR-DOS, and its story is one of the most fascinating and controversial of the whole command-line era.
The origins: Digital Research and Gary Kildall
DR-DOS was born in 1988 at Digital Research, Inc., the company Gary A. Kildall founded. Kildall was no newcomer. He had written CP/M, the operating system that dominated 8-bit microcomputers before the IBM PC arrived. The legend goes that IBM first approached Digital Research for its new machine, but the talks collapsed and the company ended up choosing Microsoft, which delivered the famous PC-DOS. That falling-out cemented a lifelong rivalry between the two firms.
With DR-DOS, Digital Research wanted its revenge: an operating system fully compatible with MS-DOS and PC DOS, but with better features. DR-DOS was in fact derived from Concurrent PC DOS, which gave it a solid, mature foundation to build on.
The key versions
The first release, in 1988, was numbered 3.31 on purpose, to match the version MS-DOS had at the time. The real breakthrough came in 1990 with DR DOS 5.0, the first one sold at retail to the general public. It was a critical success and turned DR-DOS into Microsoft’s main rival. It bundled ViewMAX (a simple graphical interface), the advanced MemoryMAX memory manager, disk caching, the BatteryMAX power-saving system for laptops and a set of file-transfer utilities. Microsoft took more than a year to answer with its own version 5.0.
In 1991 came DR DOS 6.0, which added TASKMAX, a task switcher compatible with the industry-standard task-switching API. A caveat is worth making here. Digital Research’s own Multiuser DOS ran applications in preemptively multitasked virtual DOS machines, but the DR DOS 6.0 switcher simply froze background applications until they were brought back to the foreground. Even so, it was a remarkably advanced feature for its time.
That same 1991, Novell acquired Digital Research, and the next release arrived in 1994 under the name Novell DOS 7.0, this time with genuine multitasking and networking support. Later, in 1996, Novell sold the product line to Caldera, which was looking for a DOS to bundle with its OpenLinux distribution. Under Caldera the system was released partly as open source and, for a short while, under the name OpenDOS. The last desktop version, Caldera DR-DOS 7.03, shipped in 1999.
The AARD code scandal
The most notorious story in DR-DOS history is about foul play. The beta releases of Windows 3.1 contained a chunk of code known as the AARD code, which checked whether the underlying operating system was DR-DOS rather than MS-DOS. When it found one, it threw up a cryptic error: “Non-fatal error detected… Press Enter to exit or C to continue.” The message was entirely false, since Windows ran perfectly well on DR-DOS, but Microsoft used it to sow doubt and scare users away.
When Caldera took over DR-DOS, it sued Microsoft in 1996 for deliberately creating incompatibilities, generating fake error messages and denying DR-DOS developers access to the Windows 3.1 beta code. The case never reached trial: on 7 January 2000 Microsoft settled out of court. The figure stayed secret until 2009, when it came out that it had been US$280 million.
The legacy of DR-DOS
DR-DOS proves that the best technology does not always win in the marketplace. Its memory management, its interface and its utilities forced Microsoft to improve MS-DOS in a hurry, and every user benefited from that. Today, free software enthusiasts have an open alternative in FreeDOS, which keeps the command-line flame alive. And although DR-DOS later ended up in the hands of embedded systems vendors, it is still remembered as the bold competitor that dared to stand up to the giant.