http://www.bitsavers.org/pdf/bellLabs/unix/
here is a note from Dennis about the history of the documents
that I've just put up on bitsavers
--
The manual is the 1st edition, a scan of which has been available at
http://cm.bell-labs.com/cm/cs/who/dmr/1stEdman.html
in various forms (all renditions of the same scan) for a while.
However, the annotated OS and software scan is new to me This is
a medium-age version of the assembler system for the
PDP 11/20, and is apparently without an MMU. A good find!
There were subsequent assembler versions for the (DEC Special Systems)
11/20 with an MMU and then for a while for the 11/45;
the first C version would appear late summer of 1973.
Regards and thanks,
Dennis