类的继承（上课用）

源程序：

#include <iostream>
using namespace std;
class A
{
public:
  virtual void printMe()
  {
    cout<<"This is class A printing."<<endl;
  }
} ;
class B:public A
{
public:
  void printMe() 
  {
    cout << "This is class B printing."<<endl;
  }
} ;
class C:public B
{
public:
  void printMe() 
  {
    cout <<"This is class C printing."<<endl;
  }
} ;
void print(A a)
{
  a.printMe();
}
void main()
{
  B b;
  C c;
  print(b);
  print(c);
}

运行结果 ：