Inheritance is a key feature of the C++ programming language. It lets a programmer
create more and more specific versions of a class, avoiding the need for recoding.
Inheritance is important for reusability, an important goal of object oriented
programming.
If the member function of the base class was public or protected you can usually
access it just as you might access a member function of the derived class. If two member
functions share the same name, you must use the scope operator to specify which class's
function you need to use. Of course, if the member function of a base class was
declared private, it cannot be accessed directly.
If an object needs to have the traits of more than one other class, it should inherit
the data and functions of all the different classes necessary. For instance, if you
want an object that represents a picture being displayed in a window, then the class
might inherit the properties of a "picture class" and of a "window class."
The scope operator is important when using multiple inheritance because it makes it
clear to the compiler (and to programmers) which data member or function you are
referring to.
The virtual keyword is used if there is a possibility that two versions of the same
"grandparent" base class will be inherited by a derived class. Virtual tells the
compiler to use only one copy of the grandparent, to avoid ambiguity.
