title: Do I need to include libraries in my main cpp, even if it's been included in a header file?
body: <p>Say I have a file, <code>player.h</code>, and in player.h I have included the following:</p>
  <pre><code>#include &lt;iostream&gt;
  #include &lt;string&gt;
  #include &lt;vector&gt;
  #include &lt;fstream&gt;
  </code></pre>
  <p>Would I need to include these again in <code>player.cpp</code>, where I flesh out the functions declared in the header file? If I don't, do I need to include them when I run <code>main.cpp</code>, which calls the functions from my various .cpp's and .h's</p>
  <p>School never really told me whether or not to do it, so I've always included everything across the board. If it's unnecessary is there any noticeable difference between including everything multiple times and not doing so?</p>