title: IOCTL Linux device driver
body: <p>Can anyone explain me, </p>
  
  <ol>
  <li>What is <code>IOCTL</code>?</li>
  <li>What is it used for?</li>
  <li>How can I use it?</li>
  <li>Why can't I define new function that does the same work as <code>IOCTL</code>?</li>
  </ol>