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
>