title: Why std::cout instead of simply cout?
body: <p>I get these error messages for all <code>cout</code> and <code>endl</code>:</p>
  
  <pre><code>main.cc:17:5: error: ‘cout’ was not declared in this scope
  main.cc:17:5: note: suggested alternative:
  /usr/include/c++/4.6/iostream:62:18: note:   ‘std::cout’
  </code></pre>
  
  <p>After following the suggestion, everything is fine. Now I am curious, why I had to do that. We used C++ in classes before, but I never had to write a <code>std::</code> before any of those commands. What might be different on this system?</p>