Groklaw: The Daemon, the Gnu and the Penguin, Ch. 4 & 5

“In Chapter 1, I mentioned CTSS and ITS. At that time, early in
the 1960s, TECO (Tape Editor and COrrector; later, Text Editor…)
was the editor everyone used on the PDP-1 and, later, on the PDP-6.
Not only was it widely used, but just about everyone modified it.
(In RFC 681, quoted earlier, an editor ‘based on QED’ is mentioned.
QED was written by Butler Lampson, who wrote the QED text editor
for the Berkeley Time-Sharing System on the SDS 940. It was
character-oriented and based on TECO. Ken Thompson used this
version of QED while a student at Berkeley, prior to going to Bell
Labs in 1966.) Indirectly, TECO was the ancestor of vi; directly,
it was the parent of Emacs (= Editing macros for TECO).

“Interestingly, Bill Joy created vi in 1976 and Richard Stallman
(together with Guy Steele and Dave Moon) created Emacs the same
year. The original version was based on TECMAC and TMACS, two TECO
editors. Stallman and Michael McMahon ported it to the Tenex [for
the DEC-10] and TOPS-20 [for the DEC-20] operating systems…”

Complete
Story