DR-DOS

DR-DOS (DR DOS, without hyphen up to including v6.0) is an operating system of the DOS family, written for IBM PC-compatible personal computers. It was originally developed by Gary Kildall's Digital Research and derived from Concurrent PC DOS 6.0, which was an advanced successor of CP/M-86. As ownership changed, various later versions were produced as Novell DOS, Caldera OpenDOS, etc.