Concurrent DOS

Concurrent DOS is a multi-tasking operating system from Digital Research for IBM PC compatible microcomputers, evolved from its earlier Concurrent CP/M-86. In August 1983 Bruce Skidmore, Raymond D. Pedrizetti, Dave Brown and Gordon Edmonds created PC-MODE, an optional module for Concurrent CP/M-86 3.1 that gave basic compatibility with PC DOS 1.1 and MS-DOS 1.1. It was shown at COMDEX in December 1983 and shipped to hardware vendors in March 1984 as Concurrent DOS 3.1. Simple DOS programs that did not touch the screen or other hardware directly could run, while programs such as the WordStar word processor needed native Concurrent CP/M versions. Concurrent DOS 3.2 of 1984 also ran PC DOS 2.0 applications, and its variant for IBM PC-compatible hardware was named Concurrent PC DOS. The 68000 and 286 versions later evolved into FlexOS, and the PC line continued as Multiuser DOS.