** Start of listing of h1.c **
#include <stdio.h>
#include <time.h>
#include <stdlib.h>

int main(void) {
  time_t t;
  struct tm* ptm;
  char* sTime;
  int slen;
  char* ip;
  char* path;

  printf("Content-type: text/plain\n\n");

  t = time(NULL);
  ptm = localtime(&t);
  sTime = asctime(ptm);
  slen = strlen(sTime);
  sTime[slen-1] = sTime[slen]; /* Copy null byte to clobber newline. */
  slen = strlen(sTime);
  printf("The time is %s in California.\n\n", sTime);

  ip = getenv("REMOTE_ADDR"); /* Compiler warning:
				 assignment makes pointer from integer
				 without a cast. Never warned stdlib missing */
  printf("The IP number %s is where your client/browser is located.\n\n", ip);

  path = getenv("PATH"); /* Compiler warning as above. */
  printf("The PATH is %s currently\n", path);
  printf("(the only environment variable common to both CGI and login)\n");
  return 0;
}
** End of listing of h1.c **

Here is the directory entry for that source file:
-rw-------  1 rem  user  862 Feb 14  2007 h1.c
   ^ Note user execute permission *not* needed for source files.

That gets compiled to a.out, but then renamed to something.cgi
so that it will be usable by remote users via CGI:
-rwx------  1 rem  user  5257 Feb 14  2007 h1-c.cgi
   ^ Note user execute permission needed for all CGI programs.
(because compiled-C is native machine code run directly on machine)