Back in my student days for DOS-based labs we just did

  char foo[640*1024];
  int main(int argc, char ** argv) { return 0; }

When ran, it made the OS say "Out of memory" and then it was lab assistant's headache to unload all that resident stuff that was sitting there and eating good 20-30% of available RAM. They typically opposed to doing that, so the TAs assumed the program actually worked. The end :)