title: C++ why use public, private or protected inheritance?
body: <p>Well there is enough information about this subject. For example this thread was very clear to me: <a href="https://stackoverflow.com/questions/860339/difference-between-private-public-and-protected-inheritance-in-c">Difference between private, public, and protected inheritance</a></p>
  
  <p>Except one point; Why is it useful?</p>