Virtual Function using C++

/* Programmer: ARUN ANOOP M
   Job Details: Asst.professor,CSE,MESCE */
/* Virtual Function */
#include<iostream.h>
#include<conio.h>
class B
{
public:
virtual void show()               //Vf are used to avoid duplication
{
cout<<"B"<<"\n";
}
};
class D1:public B
{
public:
void show()
{
cout<<"D1"<<"\n";
}
};
class D2:public B
{
public:
void show()
{
cout<<"D2";
}
};
void main()
{
clrscr();
B *p;
B base1;
D1 der1;
D2 der2;

p=&base1;
p->show();

p=&der1;
p->show();

p=&der2;
p->show();

getch();
}