The earliest versions of the very first C compiler, known to be written by the Dennis Richie himself.
Directory last1120c is a saved state of the compiler just before the migration from the PDP-11/20, which did not have multiply or divide instructions, but instead a provided a separate, optional unit that did these operations (and also shifts) by storing the operands into memory locations.
The second directory, prestruct-c is a copy of the compiler just before adding structures functionality.
It's not possible to compile it nowadays using any modern C compilers like GCC, however, in theory there's a probability of success compiling it using PDP-11/UNIX emulator.