title: Whitespace replace in C language
body: <p>What is the right way to replace a white space with <code>_</code> in string passCode with 2 characters? 
  In the end it should input/output: <code>(a )</code> → <code>(a_)</code>. Is there a way to do this using the isspace?</p>
  
  <pre><code>isspace(passCode[2]) == 0;
  </code></pre>