Confused about C++ classes when wanting to use them in another CPP. [Coming from C#]
<p>In OOP, you want to break apart a program into multiple classes.  </p>

<p>In C#, you would do as such:</p>

<pre><code>namespace a
{
  public class ClassA
  {
     //Methods...that are defined and have code in them.

  }
}
</code></pre>

<p>and to use that class, you just do "using namespace a;".</p>

<p>Say I want to create a class in C++, and define them, and put code in them.</p>

<pre><code>class ClassA
{
  public:
   void methodA();
}

ClassA::methodA()
{
  //implementation.
}
</code></pre>

<p>To access this implementation, you would just use #include "ClassA.h".  I fully understand that, and then you have to implement that code again?  That seems counterproductive as I like to spread my project over a lot of classes.</p>

<p>So what would be the proper procedure to implement ClassA and not re-implement all it's methods again?</p>
