Dennis Ritchie has placed some of the earliest surviving C compilers up on
his web page at The web page primevalC.html
describes the history and features of both compilers.

The two -bits files are the original V2 tap archives. There are matching
.tar.gz files with file timestamps preserved. If you want to use these
compilers, then the binaries and a suitable emulator are available via
anonymous ftp at in the directory pub/PDP-11/Sims/Apout.

The prestructc compiler can be compiled using the above binaries with a few
source code changes. The changed source is in fixed_prestructc.tar.gz,
which also includes a context diff file showing the changes made to it.
0 README 2000-01-13 00:00:53Z 721 B text/plain; charset=utf-8
1 fixed_prestructc.tar.gz 2000-01-12 23:59:12Z 21 KiB application/gzip
2 last1120c-bits.gz 2000-01-10 21:09:51Z 77 KiB application/gzip
3 last1120c.tar.gz 2000-01-10 21:14:42Z 76 KiB application/gzip
4 prestructc-bits.gz 2000-01-10 21:09:52Z 14 KiB application/gzip
5 prestructc.tar.gz 2000-01-10 21:14:43Z 13 KiB application/gzip
6 primevalC.html 1999-07-29 05:40:22Z 7.8 KiB text/html