#include<iostream>
using namespace std;

class B{};
class D : public B {};

void main()
{
	B b;
	D d;
	B* pb;
	D* pd;

	pb = &b; //works
	pb = &d; //works
	pd = &d; //works
	//pd = &b; // will never work (a derived class pointer can not point to a base class object)
	
	pb = pd; //works without a typecast
	pd = (D*)pb; //works only with a typecast

	//d = b; //the = operator would have to be overloaded to make this work
	b = d;	//this works without a typecast
}