[Someone]

See also http://www.ioccc.org/1984/mullender.c (30 years ago). Hint at http://www.ioccc.org/1984/mullender.hint

[sirclueless]

Not having access to a PDP-11 (maybe this works on an emulator?) is it cheating to ask what the output of this program is?

[Someone]

According to http://www.ioccc.org/faq.html, it is equivalent to

  main(){
    int i=512;
    do
      write(1,"  :-)\b\b\b\b",9),usleep(i);
    while(--i);
  }

So, it moves a smiley on the screen, at increasing speed.