Primeval C: two very early compilers
cs.bell-labs.com
cs.bell-labs.com
Since some of the original PDP-11 line printers (LP11's) didn't have lower case, upper case was indicated by struck-through upper case and lower case was plain upper.
I remember, after being steeped in Lisp-family languages (ECL), but also Bliss-11 (from CMU), my curiousity at seeing a "high-level" language that was so close to the machine in a different way than Bliss (which had a lot to recommend it) but also with a completely different approach to data structures. (C grew out of BCPL, while Bliss used what were effectively compile-time procedures to let you arbitrarily define your structure access.)
http://www.digiater.nl/openvms/freeware/v80/bliss-intro/
http://www.digiater.nl/openvms/freeware/v80/bliss-article/
http://www.digiater.nl/openvms/freeware/v80/bliss-article-ps...
Bliss32 and Bliss64 compilers for VAX/VMS, Alpha, and Itanium:
http://www.digiater.nl/openvms/freeware/v80/bliss/
That includes (free) licenses. If you want to use these compilers to experiment, you can get a VAX emulator here http://simh.trailing-edge.com/ (boots and runs on Linux, Mac, Windows) and a VMS license and media are available for the cost of a CD (US$30).
http://news.ycombinator.com/item?id=2505688
Especially:
Book: Lion's Commentary on the Sixth Ed Unix
The Development of the C Language