一定要使用指针吗?

#include<iostream.h>
class Grandam {
    public:
      virtual void introduce_self()  // 定义虚函数introduce_self()
      { cout<<"I am grandam."<<endl; }
    };
class Mother:public Grandam {
    public:
        void introduce_self()     // 重新定义虚函数introduce_self()
        { cout<<"I am mother."<<endl;}
};
class Daughter:public Mother {
    public:
        void introduce_self()     // 重新定义虚函数introduce_self()
        { cout<<"I am daughter."<<endl;}
};
void main()
{
    Grandam *ptr;
    Grandam g;
    Mother m;
Daughter d;
     ptr=&g;
     ptr->introduce_self(); //调用基类Grandam的introduce_self()
     ptr=&m;
     ptr->introduce_self(); // 调用派生类Mother的introduce_self()
     ptr=&d;
     ptr->introduce_self();    //调用派生类
                                               //  Daughter的introduce_self()
}