title: Include guard conventions in C
body: <p>What is the conventional way to set up your include guards?  I usually write them as (for example.h):</p>
  
  <pre><code>#ifndef _EXAMPLE_H_
  #define _EXAMPLE_H_
  #include "example.h"
  #endif
  </code></pre>
  
  <p>Does underscore convention matter?  I've seen conflicting information when I googled this.  Does the <code>_EXAMPLE_H_</code> even have to match the name of the header?</p>