Page 226 - DCAP404 _Object Oriented Programming

Unit 10: Virtual Functions and Polymorphism

2. A virtual function is a member function of a base class and relies on a specific object to Notes
determine which implementation of the ………………………… is called.
3. If a function is declared ………………………… in its base class, you can still access it
directly using the scope resolution (::) operator.
4. If you do not override a virtual member function in a derived class, a call to that function
uses the function implementation defined in the…………………....
5. If you declare a base class destructor as virtual, a derived class destructor will
………………………… that base class destructor, even though destructors are not inherited.

10.2 Pure Virtual Functions

Generally a function is declared virtual inside a base class and we redefine it the derived classes.
The function declared in the base class seldom performs any task.
The following program demonstrates how a pure virtual function is defined, declared and
invoked from the object of a derived class through the pointer of the base class. In the example
there are two classes employee and grade. The class employee is base class and the grade is
derived class. The functions getdata ( ) and display ( ) are declared for both the classes. For the
class employee the functions are defined with empty body or no code inside the function. The
code is written for the grade class.

!

Caution The methods of the derived class are invoked by the pointer to the base class.
#include <iostream.h>
#include<conio.h>
class employee {

int code;
char name [20];

public:
virtual void getdata ( );
virtual void display ( );
};
class grade: public employee
{
char grd [90];

float salary;
public:
void getdata ( );
void display ( );
};
void employee :: getdata ()

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