title: What's the difference between C header files (.h) and C++ header files (.hpp)?
body: <p>I noticed that the boost library uses header files of (<code>.hpp</code>).<br>
  I am curious since most source files I see use normal <code>.h</code> header files.<br>
  Could there be any special instances which warrant use of <code>.hpp</code> instead of <code>.h</code> ?</p>
  
  <p>Thanks</p>