title: Correct way of defining NULL and NULL_POINTER?
body: <p>As far as I know, <strong>C</strong> defines <code>NULL</code> like this:</p>
  
  <pre><code>#define NULL ( (void *) 0)
  </code></pre>
  
  <p>Then, how should we define <code>NULL_POINTER</code> ? I defined it the same in my program and it worked, but I suppose that is just a coincidence:</p>
  
  <pre><code>#define NULL_POINTER ( (void *) 0)
  </code></pre>
  
  <p>What would be the logical definition, if any ?</p>