title: Measuring time in C
body: <p>I'm trying to measure some activity in C (Matrix multiplying) and noticed that I should do something like this:</p>
  
  <pre><code>clock_t start = clock();
  sleep(3);
  clock_t end = clock();
  double elapsed_time = (end - start)/(double)CLOCKS_PER_SEC;
  printf("Elapsed time: %.2f.\n", elapsed_time);
  </code></pre>
  
  <p>The output is:</p>
  
  <pre><code>Elapsed time: 0.00.
  </code></pre>
  
  <p>Why is this happening?</p>