"In spring 1969, AT&T decided to terminate its involvement
in a project called Multics--Multiplexed Information and Computing
Service--which had been started in 1964 by MIT, GE and Bell Labs.
This left those at AT&T Bell Labs who had been working on the
project--notably Doug McIlroy, Dennis Ritchie and Ken Thompson--at
loose ends. Doug immediately got involved with other things in
Murray Hill, NJ, but Dennis and Ken had been interested in the
project per se and wanted to explore several of its ideas.
"Ken has said:
"Dennis and [Rudd] Canaday and I were discussing these ideas of
the general nature of keeping the files out of each other's hair
and the nitty-gritty of expanding, of the real implementation where
you put block addresses..."