title: How do I change the extension of many files in a directory?
body: <p>Suppose I have a large number of files in a directory with <code>.txt</code> extension.</p>
  
  <p>How can I change the extension of all these files to <code>.c</code> using the following command line environments:</p>
  
  <ul>
  <li>Powershell in Windows </li>
  <li>cmd/DOS in Windows</li>
  <li>The terminal in bash</li>
  </ul>