title: Difference between using #include<filename> and #include<filename.h> in C++
body: <p>What is the difference between using <code>#include&lt;filename&gt; and #include&lt;filename.h</code>> in <a href="http://en.wikipedia.org/wiki/C%2B%2B" rel="noreferrer">C++</a>? Which of the two is used and why is it is used?</p>