Highly interesting!
main(argc, argv)
int argv[];
This is a culture shock. Did the PDP-11 not distinguish between `char` and `int`? Of course it did -- this was one of the distinguishing features (byte addressing) of the PDP-11 vs the original machine that ran UNIX, the PDP-7, after all ;-)
In "ancient"/K&R C, types weren't specified with the parameters, but on the following lines afterwards. GCC would still compile code like this, if passed the -traditional flag, until ... some point in the last decade or so. Still, this style was deprecated with ANSI C/C89, so it had a good run.
I find even more interesting that in a later version this appears:
main(argc, argv)
char argv[][];
Which sadly is no longer valid in C.