The paper with that quote is still linked from dmr's page:

On Wed, Jun 18, 2014 at 11:03 AM, Norman Wilson <> wrote:
  Interesting - what's your source?  It was also my understanding they
  used the -7 'because it was there' but that they had pitched for a
  PDP-10, which had TOPS-10.


I think Doug's source is in the class `personal observation.'
He was there at the time; Ken and Dennis's department head, if
I've got it right.

Remember that Bell Labs had just disengaged itself from the
Multics project.  The interest in a new OS sprang partly
from the desire to have a comfortable multi-user system
now that Multics was no longer available.  That's why the
DEC operating systems of the time, which were (as I understand
it) simple single-user monitors, didn't fill the bill.

The character of the players matters too: remember that
Ken is the guy who one night sat down to write a Fortran
compiler because real systems have Fortran, and ended up
inventing B instead.

I've read that there was indeed a pitch to buy a PDP-10; that
there was some complicated plan to lower the effective cost;
and that upper management (not Doug) turned it down because
`Bell Labs doesn't do business that way.'  I think I got that
from Dennis's retrospective paper, published in the 1984
all-UNIX issue of the Bell Labs Techical Journal, a must-read
(along with the late-1970s all-UNIX issue of BSTJ) for anyone
on this list.
TUHS mailing list