Why in C++ do I need to use namespace after already using import directive?
<p>In C# one only uses an using directive for a namespace. In C++ like in this example below, one must do an include then use a namespace, why isn't it the same thing like in C# ?</p>

<pre><code>#include &lt;iostream&gt;

int main()
{
   using namespace std;
   cout &lt;&lt; "Hello world!" &lt;&lt; endl;
   return 0;
}
</code></pre>
