Thread: Virtual functions, confusion

I am trying to understand the sense of virtual fuctions and so I wrote the following piece of code:

Code:

#include <iostream>
using namespace std;

class Base
{
public:
	virtual void doit() { cout << "Base" << endl; }
};

class Derived : public Base
{
public:
	virtual void doit() { cout << "Derived" << endl; }
};

int main()
{
	Base b;
	Derived d;

	Base &reference = b;
	reference.doit();
	reference = d;
	reference.doit();
}

When I compile it, I get:

Code:

Base
Base

Why? Shouldn't the second call return "Derived"?

Conversely, when I write:

Code:

int main()
{
	Base b;
	Derived d;

	Base &reference = d;
	reference.doit();
	reference = b;
	reference.doit();
}

It returns:

Code:

Derived
Derived

What is the point of the virtual functions if by re-assigning the reference to a different type, it still uses the old function?