940115-1.c

this is a gcc file, you can download it and learn its usetility, for further detail please look at t

f (cp, end)
     char *cp;
     char *end;
{
  return (cp < end);
}

main ()
{
  if (! f ((char *) 0, (char *) 1))
    abort();
  exit (0);
}