Derived classes.

Write a C++ program to illustrate ‘this’ pointer and pointers to derived classes.

#include<iostream.h>

#include<conio.h>

class BC

{

public:

int b;

void show()

{

cout<<"b= "<<b<<endl;

}

BC findlarge(BC obj)

{

if(b>obj.b)

return *this;

else

return obj;

}

};

class DC:public BC

{

public:

int d;

void show()

{

cout<<"b= "<<b<<endl;

cout<<"d= "<<d<<endl;

}

};

int main()

{

clrscr();

BC b1,b2;

b1.b=10;

b2.b=20;

BC Large=b1.findlarge(b2);

cout<<"\n Largest is :";

Large.show();

BC *bptr;

BC base;

bptr=&base;

bptr->b=100;

cout<<"Base pointer to base class\n";

bptr->show();

DC derived;

bptr=&derived;

bptr->b=200;

cout<<"Base pointer to base class\n";

bptr->show();

DC *dptr;

dptr=&derived;

dptr->d=300;

cout<<"Derived pointer to derived class\n";

dptr->show();

((DC*)bptr)->d=400;

cout<<"Type conversion\n";

((DC*)bptr)->show();

getch();

return 0;

}

Output of the above program is:

Largest is :b= 20

Base pointer to base class

b= 100

Base pointer to base class

b= 200

Derived pointer to derived class

b= 200

d= 300

Type conversion

b= 200

d= 400

Thanks

Mukesh Rajput