What do you mean by Pure Virtual function?

What do you mean by Pure Virtual function?

A pure virtual function has no definition related to the base class. Only the function prototype is included to make a pure virtual function the following syntax is used:

virtual return_type function_name(par_list) = 0;

The following is an example program:

Program Code:

#include<iostream>

using namespace std;

// definition of base class area

class area

{

double x,y;

public:

void set_area(int a,int b) // definition of member function of class area

{

x=a;

y=b;

}

void get_dim(double &a,double &b) // definition of member function of class area

{

a=x;

b=y;

}

virtual double get_area()=0; // declaration of  pure virtual function

};

// definition of derived class rectangle

class rectangle : public area

{

public:

double get_area() // definition of  pure virtual function in derived class rectangle

{

double a,b;

get_dim(a,b);

return a*b;

}

};

class triangle : public area

{

public:

double get_area() // definition of  pure virtual function in derived class triangle

{

double a,b;

get_dim(a,b);

return 0.5*a*b;

}

};

// definition of main() function 

int main()

{

area *p;

rectangle r;

triangle t;

r.set_area(3,4);

t.set_area(4,5);

p=&r;

cout<<"Area of rectangle is : "<<p->get_area();

cout<<endl;

p=&t;

cout<<"Area of triangle is : "<<p->get_area();

cout<<endl;

return 0;

}

The program output is tested on www.jdoodle.com

Output:

Area of rectangle is : 12

Area of triangle is : 10

Thanks

Mukesh Rajput