PURE VIRTUAL FUNCTION

PURE VIRTUAL FUNCTION

A pure virtual function is a virtual function declared in the base class, but there is no definition for the virtual function, so that it can be overridden by the derived classes. When a function is declared as virtual function in a class, then that class cannot be used to declare any object because it becomes an abstract class.

SYNTAX:

virtual return-type function-name (args) =0;

Example:

class Base

{

public:

virtual void greet()=0;   // pure virtual function

};

class derived: public Base

{

public:

void greet()

{

cout<<”I am derived class”;

}

};

void main()

{

derived Obj;

Obj.greet();

}

Output:

Hi! I am derived class

Virtual functions

Abstract Class