Page 231 - DCAP404 _Object Oriented Programming

Object-oriented Programming

Notes accessed in the same manner even though specific actions associated with each operation may
differ. Polymorphism is extensively used in implementing inheritance as shown below.

shape
Draw()

Object circle Object box Object triangle

Draw(circle) Draw(box) Draw(tr iangle)

Polymorphism can be implemented using operator and function overloading, where the same
operator and function works differently on different arguments producing different results.
These polymorphisms are brought into effect at compile time itself, hence is known as early
binding, static binding, static linking or compile time polymorphism.
However, ambiguity creeps in when the base class and the derived class both have a function
with same name. For instance, let us consider the following code snippet.
Class aa
{
Int x;
Public:

Void display() {……} //display in base class
};
Class bb : public aa
{
Int y;
Public:
Void display() {……} //display in derived class

};
Since, both the functions aa.display() and bb.display() are same but at in different classes, there
is no overloading, and hence early binding does not apply. The appropriate function is chosen
at the run time – run time polymorphism.
C++ supports run-time polymorphism by a mechanism called virtual function. It exhibits late
binding or dynamic linking.
As stated earlier, polymorphism refers to the property by which objects belonging to different
classes are able to respond to the same message, but in different forms. Therefore, an essential
feature of polymorphism is the ability to refer to objects without any regard to their classes. It
implies that a single pointer variable may refer to object of different classes.
However, a base pointer, even if is made to contain the address of the derived class, always
executes the function in the base class. The compiler ignores the content of the pointer and

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