Simple example of "virtual" usage to explain it to beginners

virtual.cc

#include <iostream>
class Foo {
public:
	Foo() {}
	virtual void speak() {std::cout << "I'm foo" << std::endl;}
	void talk() {std::cout << "I'm still foo" << std::endl;}
};
class Bar : public Foo {
public:
	Bar() {}
	void speak() {std::cout << "I'm bar" << std::endl;}
	void talk() {std::cout << "I'm still bar" << std::endl;}
};
int main() {
	/* With pointers */
	Foo * fp = new Foo;
	Bar * bp = new Bar;
	Foo * fbp = new Bar;
	fp->speak(); /* I'm foo */
	fp->talk(); /* I'm still foo */
	bp->speak(); /* I'm bar */
	bp->talk(); /* I'm still bar */
	fbp->speak(); /* I'm bar */
	fbp->talk(); /* I'm still foo */
	delete(fp);
	delete(bp);
	delete(fbp);

	/* Without pointers */
	Foo f;
	Bar b;
	Foo & fbr = b;
	Foo fb = b;
	f.speak(); /* I'm foo */
	f.talk(); /* I'm still foo */
	b.speak(); /* I'm bar */
	b.talk(); /* I'm still bar */
	fbr.speak(); /* I'm bar */
	fbr.talk(); /* I'm still foo */
	fb.speak(); /* I'm foo */
	fb.talk(); /* I'm still foo */

	return 0;
}