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.