#include <iostream>

class Bird                 // the "generic" base class
{
public:
  virtual void OutputName() {std::cout << "a bird";}
  virtual ~Bird() {}
};

class Swan : public Bird   // Swan derives from Bird
{ 
public:
  void OutputName() {std::cout << "a swan";} // overrides virtual function
};

int main()
{
  Bird* myBird = new Swan; // Declares a pointer to a generic Bird,
                           // and sets it pointing to a newly-created Swan.

  myBird->OutputName();    // This will output "a swan", not "a bird".

  delete myBird;

  return 0;
}