** Start of listing of h2.c **
#include <stdio.h>
#include <string.h>
#include <time.h>
#include <stdlib.h>

int main(void) {
  time_t t;
  struct tm* ptm;
  char* sTime;
  int slen;
  char* ip;
  unsigned char *rmstr;
  unsigned char *qus;
  char qt = '"';

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

  printf("Working on new stuff...\n");
  rmstr = getenv("REQUEST_METHOD");
  if (rmstr == NULL) {
    printf("Request method returned NULL, why??\n");
    return -1;
  } else {
    printf("The request method is: [%s]\n", rmstr);
  }

  if (strcmp(rmstr,"POST") == 0) {
    printf("*** POST method not yet implemented\n");
    return -1;
  } else if (strcmp(rmstr,"GET") == 0) {
    qus = getenv("QUERY_STRING");
    printf("The query string is: [%s]\n", qus);
  } else {
    printf("*** Unknown request method, neither GET nor POST\n");
    return -1;
  }
  printf("* End of debug output.\n\n");

  if (strstr(qus,"date") == NULL) {
    printf("You didn't ask for %cdate%c this time.\n", qt, qt);
  } else {
    printf("The string %cdate%c occurred, so here it is:\n", qt, qt);
    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", sTime);
  }
  printf("\n");

  if (strstr(qus,"IP") != NULL) {
    ip = getenv("REMOTE_ADDR");
    printf("The IP number %s is where your client/browser is located.\n",
	   ip);
  } else if (strstr(qus,"ip") != NULL) {
    printf("No, the key %cIP%c must be in upper case to work here!\n", qt, qt);
  } else {
    printf("You didn't ask for %cIP%c this time.\n", qt, qt);
  }
  printf("\n");

  if (strstr(qus,"name") != NULL) {
    printf("My name is Robert Elton Maas.\n");
  } else {
    printf("You didn't ask for %cname%c this time.\n", qt, qt);
  }
  return 0;
}
** End of listing of h2.c **

Here is the directory entry for that source file:
-rw-------  1 rem  user  1861 Feb 14  2007 h2.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  6527 Jul 11  2005 h2-c.cgi
   ^ Note user execute permission needed for all CGI programs.
(because compiled-C is native machine code running directly on machine)