why are we using &rBase instead of rBase?

I have read the chapter on reference but still can’t figure it out.

Please do reply.

To be specific, this code:

class Base
{
protected:

public:
    virtual const char* GetName() { return "Base"; } // virtual keyword here
};

class Derived: public Base
{
public:
   const char* GetName() { return "Derived"; } // note lack of virtual keyword here
};

class DerivedTwice: public Derived
{
public:
    const char* GetName() { return "DerivedTwice"; }
};

int main()
{
    DerivedTwice cDerivedTwice;
    Derived &rDerived = cDerivedTwice;
    cout << "rDerived is a " << rDerived.GetName() << endl; // outputs "rDerived is a DerivedTwice"
                                                            // despite lack of second virtual keyword.

    return 0;
}

outputs the “rDerived is a DerivedTwice” being looked for, when compiled with VS’05. Other compilers might require the second keyword.

Can you tell me conceptually why the need of virtual functions came into picture? i do understand the concept but what is the necessity, just to reduce overhead ..but calling virtual function itself is an overhead????

Wonderful explanations all around.
Way better than most textbooks.

Only one point that has confused the daylights out of me.

15. int  main()
16. {
17.    Derived cDerived;
18.    Base &rBase = &cDerived;
19.    cout << "rBase is a " << rBase.GetName() << endl;
20.
21.    return 0; }

I believe rBase is a “reference”, not a “pointer.”
if it were

18.    Base *rBase = &cDerived;

Then it would be a pointer.

Thanks!

Raj