title: When to use include guards or #pragma once C++
body: <p>Is it good practice to use your choice of either/both include guards and <code>#pragma once</code> in <em>every</em> header file, or just those with something such as a class declaration?</p>
  
  <p>I am tempted to put it in every header, but I'm afraid it would be unneeded and only add to the compile time. What is good practice or common to do?</p>
  
  <p>Let me clarify: I understand the difference between the two. I am asking whether by experience programmers use it in <strong>every</strong> file or just those that require it.</p>