DR-DOS

DR-DOS is short for Digital Research DOS, an MS-DOS compatible operating system produced by Digital Research, the makers of CP/M. DR-DOS was eventually bought by Novell who renamed it Novell DOS. Caldera later bought the product from Novell and renamed it OpenDOS before deciding to call it DR-DOS again.

Short for Digital Research Disk Operating System, DR-DOS was one of several competing versions of DOS available on IBM compatible personal computers in the early 1990s. With the cost of RAM decreasing, many PCs were being equipped with more than the 640KB that DOS would recognize, so DR-DOS's superior handling of memory beyond the 640KB barrier made it an appealing and less expensive alternative to other versions of DOS.

Since DR-DOS competed head-to-head against Microsoft's MS DOS, Microsoft intentionally sabotaged the new version of their own flagship graphical operating system, Windows 3.1, so it would refuse to work properly on machines which used DR-DOS. This organized FUD attack arguably led to the disappearance of Digital Research from the desktop operating system market, and would definitely not be the last FUD attack in Microsoft's battle for market share.