How inheritance helps in building class hierarchies in c plus plus?

Answer 1

Inheritance allows you to derive new objects from existing objects, thus allowing you to re-use the existing code (known as the generic code), augmenting or overriding that existing code in order to provide more specialised functionality (the specialised code).

For instance, if you have a Rectangle class, you might choose to derive a Square class from the Rectangle class. Thus the Square class inherits all the properties of a Rectangle (such as 4 vertices and 4 edges meeting at 90 degrees), but specialises the class to ensure that all four edges are always equal length. In other words, a Square is a more-specialised form of Rectangle, and therefore need only cater for the properties that are unique to Squares, whilst inheriting all the properties that are common to both Squares and Rectangles.

This is not unlike the real-world where you will often adapt an existing object to suit a new purpose, rather than build a new object completely from scratch, thus saving you a lot of time and money. In other words, we don't spend our time continually re-inventing wheels, we simply use an existing wheel and adapt it to suit our needs. The more closely the existing wheel resembles the wheel we actually want, the less work we have to do to adapt it.

Answer 2

The same way that inheritance helps build families of people. Children inherit genes from their parents and grandparents, just as child classes inherit the public and protected properties of their parent and grandparent classes, the base classes. By inheriting those properties, the most-derive classes are blessed with ready-made functionality. This allows us to create new classes from tried and tested existing classes, creating more specialised classes, without re-writing any of the existing code. We only need to cater for the differences, the specialities.