C++ include header problem
<p>I am new to c/c++, I am confused about followings:</p>

<ol>
<li>Whether I should put class declarations in its own header file, and actual implementation in another file?</li>
<li>Whether I should put headers like <code>&lt;iostream&gt;</code> in the example.h file or in example.cpp file?</li>
<li>If all the classes need to use <code>&lt;iostream&gt;</code>, and I include a class's header file into another class's header, does it mean I included <code>&lt;iostream&gt;</code> twice?</li>
<li>If I use a lot STL classes, what is a good practice to use <code>std::</code>?</li>
</ol>
