title: The easiest way to convert multi-digit char to integer
body: <p>Let's say here is a char with unknown digit number in C:</p>
  
  <pre><code>char char_id[1000] = {'1', '2', '3', ..., '8', '9', '\0'};
  </code></pre>
  
  <p>If I want the last two digit to form an integer i.e. '89'.</p>
  
  <p>What is the easiest way?</p>