Page 220 - DCAP404 _Object Oriented Programming

Unit 10: Virtual Functions and Polymorphism

virtual int sum (int xx, int IT); //base class Notes
virtual float sum (int xx, int IT); //derived class
Both the above functions can be written with int data types in the base class as well as in the
derived class as
virtual int sum (int xx, int yy); //base class
virtual int sum (int xx, int yy); //derived class
Only a member function of a class can be declared as virtual. A non member function (nonmethod)
of a class cannot be declared virtual.
virtual void display () //error, nonmember function
{
Function body

}
10.1.1 Late Binding

Late binding means selecting functions during the execution. Though late binding requires
some overhead it provides increased power and flexibility. The late binding is implemented
through virtual functions as a result we have to declare an object of a class either as a pointer to
a class or a reference to a class.

Did u know? What is static binding?
By default, C++ matches a function call with the correct function definition at compile
time. This is called static binding.
For example the following shows how a late binding or run time binding can be carried out with
the help of a virtual function.
class base {
private :
int x;
float y;
public:
virtual void display ( );

int sum ( );
};
class derivedD : public baseA
{
private:
int x;
float y;

public:

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