title: What is a clock interrupt?
body: <p>I can't find on the Internet a proper definition of this.
  I am wondering what is actually a clock interrupt and when does it occur:</p>
  
  <ul>
  <li>Does it occur every clock tick?</li>
  <li>Does it occur every second?</li>
  <li>Is it some kind of an alarm that has to be triggered?</li>
  </ul>