Qed

QED is a computer text editor.

Originally written by Butler Lampson and Peter Deutsch for the [SDS 940]? (in the 1960s?). Ken Thompson later wrote a version for CTSS?; this version was notable for introducing regular expressions. QED influenced the classic UNIX text editor ed and the less well known sam?.

History of QED

http://cm.bell-labs.com/cm/cs/who/dmr/qed.html

See also: Q.E.D.

QED is also a (sort of) widely used abbreviation of quantum electrodynamics