14_1阅读程序

#include <iostream>using namespace std;class Vehicle  //交通工具{public:    void run() const//当定义为虚函数时，指针调用同名虚成员函数，执行的是派生类的成员函数。当定义为纯虚函数时，无法直接访问对象。    {        cout << "run a vehicle. "<<endl;    }};class Car: public Vehicle  //汽车{public:    void run() const    {        cout << "run a car. "<<endl;    }};class Airplane: public Vehicle  //飞机{public:    void run() const    {        cout << "run a airplane. "<<endl;    }};int main(){    cout<<"(a) 直接用对象访问成员函数: "<<endl;    Vehicle v;    v.run();    Car car;    Airplane airplane;    car.run();    airplane.run();    cout<<"(b)用指向基类的指针访问成员函数: "<<endl;    Vehicle *vp;    vp=&car;    vp->run();    vp=&airplane;    vp->run();    return 0;}