Lecture 1 - Inheritance

Inheritance is probably the most powerful feature of object-oriented programming,
after classes themselves. Inheritance is the process of creating new classes, called
derived classes, from existing or base classes. The derived class inherits all the
capabilities of the base class but can add embellishments and refinements of its
own. The base class is unchanged by this process.
The arrow in Figure goes in the opposite direction of what you might expect. If it
pointed down we would label it inheritance. However, the more common approach
is to point the arrow up, from the derived class to the base class, and to think of it
as a “derived from” arrow Inheritance is an essential part of OOP. Its big payoff is
that it permits code reusability. Once a base class is written and debugged, it need
not be touched again, but, using inheritance, can nevertheless be adapted to work
in different situations. Reusing existing code saves time and money and increases a
program’s reliability. Inheritance can also help in the original conceptualization of
a programming problem, and in the overall design of the program. An important
result of reusability is the ease of distributing class libraries.