title: Working with clock_t in C
body: <p>I'm working on a little school project to re-code the <code>SpaceInvaders</code> Game, without using <code>ncurses</code>, but only the basic libraries, and i want to use time to print my screen-buffer every time, so i need to know when to print exactly so the user won't feel the screen lagging.</p>
  
  <p>I started using the <code>Clock_t</code> structure as a test like :</p>
  
  <pre><code>clock_t stime = clock();
  sleep(3);
  clock_t etime = clock();
  unsigned long millis = ((etime - stime) * 1000) / CLOCKS_PER_SEC;
  printf("%lu\n",millis);
  </code></pre>
  
  <p>but the output is 0 all the time, i want know why and how i can fix it so i can see milliseconds, or nanoseconds </p>