It will be great if you can add two more topics to this chapter

1) We can define body for a pure virtual function so please add when, why and how ?
2) Please add virtual table view for abstract class why compiler not letting us to instantiate abstract class or i should say class having and pure virtual function

Here is my views:
we can not make object of abstract class because, in the vtable the vtable entry for the abstract class functions will be NULL, even if there is a single pure virtual function in the class the class becomes as abstract class.Even if there is a single NULL entry in the function table the compiler does not allow to create the object.

In C++ there is also a concept called “Late binding yet static typing”. That is
When you have a pointer to object and object is derived from the type of class of type pointer, there are two types,1) type of the pointer: static 2) type of pointed-to-object: dynamic.
Here static typing means, the legality of the function call is determined by the compiler at compile time, since pointer is Base and Base has public virtual function. compiler validates the function calling. but at run time, since you have assigned the derived object address, it resolves the derived function only.

Hope this helps u.

I have learned a lot…

#include "stdafx.h"
#include "iostream"
#include "conio.h"
using namespace std;

class base
{
	public :
	int x;
	virtual void display();
};
void base::display()
{
	x =100;
	cout<<x<<" Display Base"<<endl;
}
class derived : public base
{
	void display();
};
void derived::display()
{
	x =50;cout<<x<<" Display Derived";
}
int _tmain(int argc, _TCHAR* argv[])
{
	base B1;
	derived d1;
	base *b1ptr;
	b1ptr = &B1;
	b1ptr->display();

	b1ptr = &d1;

	b1ptr->display();
	//d1.base::display();
	getch();
	return 0;
}

)

my doubt:

How am I able to access the private member of derived class function (**which is private) using base class pointer??

P.S.: Excellent website for learning C++. Thank you very much for providing this resource. I’ll be sure to refer people here when appropriate!