title: C coding and math to 15 digits of precision
body: <p>Can anyone tell me why test_value2 in this example below has a value of 1 in the 15th decimal digit?  im at a loss as to why when I add 1/10th to 1 it looks good but when I add it to larger numbers (like 20) things go wonky.
  thanks
  Kevin</p>
  <pre><code>#include &lt;stdio.h&gt;
  #include &lt;math.h&gt;
  int main()
  {
      double test_value1, test_value2;
      test_value1=10+(1/(pow(10,1)));
      test_value2=20+(1/(pow(10,1)));
  
      printf(&quot;\ntest_value1=:%0.15f&quot;,test_value1);
      printf(&quot;\ntest_value2=:%0.15f&quot;,test_value2);
  
     return 0;
  }
  </code></pre>
  <p><strong>output:</strong></p>
  <pre><code>test_value1=:10.100000000000000
  test_value2=:20.100000000000001
  </code></pre>