利用虚函数实现多态性

#include<iostream>
#include<string>
using namespace std;
class Student
{
public:
Student(int n,string nam,int s):num(n),name(nam),score(s) {}
virtual void display()
{
cout<<"num: "<<num<<endl;
cout<<"name: "<<name<<endl;
cout<<"score: "<<score<<endl;
}
protected:
int num;
string name;
int score;
};
class Graduate:public Student
{
public:
Graduate(int n,string nam,int s,int w):Student(n,nam,s),wage(w){}
void display()
{
cout<<"num: "<<num<<endl;
cout<<"name: "<<name<<endl;
cout<<"score: "<<score<<endl;
cout<<"wage: "<<wage<<endl;
}
private:
int wage;
};
int main()
{
Student stu(10010,"wang",100);
Graduate Grad(10020,"zhao",99,1000);
Student *p=&stu;
p->display();
p=&Grad;
p->display();
return 0;
}