non-abstract.</p>

<p>For example, the following class is abstract:</p>

<pre class="cpp">
class printable
{
public:
  void print(std::ostream&amp;) const = 0;
};
</pre>

<p>This class is abstract because the print method is abstract. Such a class
would define an interface to a printable object - so its name reflects its
usage. Interface classes tend to have adjectives as names. The methods as
usual in C++ are verbs.</p>

<p>In this case, the class has only one method and it is abstract. This is a
pure inte