title: What is extern volatile pointer
body: <p>What is extern volatile pointer.</p>
  
  <pre><code>extern volatile uint32 *ptr;
  </code></pre>
  
  <p>Here, what will be the behavior of *ptr?
  What does this actually mean?</p>
  
  <p>And, when it should be used?</p>
  
  <p>I have tried to google about it, but didn't get any satisfactory answer, there is not much info present about this combination.</p>