Acronym for Digital Equipment Corporation
Produced the famous PDP11 machines which saw widespread use in the 1970s. They made VAX machines, first as PDP11s running exotic MicroCode then as an architecture in their own right, which were widely used during the 1980's. Both WaikatoUniversity and CanterburyUniversity still have VAX mainframes in service. VAXs normally run the VMS operating system with Digital's Command Language (DCL) as the CLI (As pointed out by zcat(1)). They can also run unix.
Also made Alpha machines.
DEC were eventually bought out by Compaq.