title: Difference between include in .h file and .c file
body: <p>What is the difference between doing a <code>#include</code> in a <code>.h</code> file and in a <code>.c</code> file?</p>
  
  <p>For example, I have the file <code>a.h</code> and <code>a.c</code> which have the <code>class A</code>. I use <code>class A</code> in <code>class B</code> (<code>b.h</code>, <code>b.c</code>). What is the difference between doing an include:</p>
  
  <pre><code>#include "a.h"
  </code></pre>
  
  <p>in <code>b.h</code> vs <code>b.c</code>? </p>