title: difftime returning 0 when there is clearly a difference
body: <p>I have the following C99 program which measures performance of simple division operations relative to addition. However, the <code>difftime</code> function keeps returning 0 even though the program is clearly taking several seconds to process <code>runAddition</code> and <code>runDivision</code> with <code>iterations</code> set to 1 billion.</p>
  
  <pre><code>#include &lt;stdio.h&gt;
  #include &lt;time.h&gt;
  
  void runAddition(long long iterations)
  {
      long long temp;
      for (long long i = 1; i &lt;= iterations; i++)
      {
          temp = temp + i;
      }
  }
  
  void runDivision(long long iterations)
  {
      long long temp;
  
      // Start at 1 to avoid division by 0!
      for (long long i = 1; i &lt;= iterations; i++)
      {
          temp = temp / i;
      }
  }
  
  int main()
  {
      long long iterations = 1000000000;
      time_t startTime;
  
      printf("How many iterations would you like to run of each operation? ");
      scanf("%d", &amp;iterations);
  
      printf("Running %d additions...\n", iterations);
      startTime = time(NULL);
      runAddition(iterations);
      printf("%d additions took %f seconds\n", iterations, difftime(time(NULL), startTime));
  
      printf("Running %d divisions...\n", iterations);
      startTime = time(NULL);
      runDivision(iterations);
      printf("%d divisions took %f seconds\n", iterations, difftime(time(NULL), startTime));
  }
  </code></pre>