The C compiler we had at NMT that Greg Titus wrote/rewrote allowed one to pick a number

of different choices for character size (5, 6, 7 or 8). It defaulted to 7 or 8. I recall that the

defaults produced OK results for student work, but that was a bit slow for pushing the

envelope without some very careful choices. But it was good enough for me to write

my OS group project running under 'ZAYEF' a DecSystem-20 emulator running on the

DecSystem 20 under TOPS-20... My first exposure to virtual machines... It was a total

trip to have 18 bit pointers and weird interrupt semantics....

I really rather working on the VAX 11/750 in 'C' and later on the Sun3/50s more, though.

In part because the debugger was better (or at least more approachable by my

poor undergraduate mind).

Warner

On Thu, Jul 15, 2021 at 1:28 PM Clem Cole <clemc@ccc.com> wrote:

The 'second' C compiler was a PDP-10 and Honeywell (36-bit) target Alan Synder did for his MIT Thesis.
It was originally targeted to ITS for the PDP-10, but it ran on Tops-20 also.

My >>memory<< is he used a 7-bit Character, ala SAIL, with 5 chars stored in a word with a bit leftover.

You can check it out: https://github.com/PDP-10/Snyder-C-compiler

I believe that C compiler Nelson is talking about I believe is actually Synder's that Jay either ported from ITS or WAITS.

We had some form of the Synder compiler on the PDP-10's at CMU in the late 1970s.
It was either Mike Accetta or Fil Aleva that wrote a program to read PDP-10 backup tapes, that I updated to deal with TOPS-20/TENEX 'dumper' format which was similar/only different.
ᐧ

On Thu, Jul 15, 2021 at 3:03 PM Norman Wilson <norman@oclsc.org> wrote:
Nelson H. F. Beebe:

P.S. Jay was the first to get Steve Johnson's Portable C Compiler,
pcc, to run on the 36-bit PDP-10, and once we had pcc, we began the
move from writing utilities in Pascal and PDP-10 assembly language to
doing them in C.

======

How did that C implementation handle ASCII text on the DEC-10?
Were it a from-scratch UNIX port it might make sense to store
four eight- or nine-bit bytes to a word, but if (as I sense it
was) it was C running on TOPS-10 or TOPS-20, it would have had
to work comfortably with DEC's convention of five 7-bit characters
(plus a spare bit used by some programs as a flag).

Norman Wilson
Toronto ON