六百里加急：为什么在基类的get（）函数前加上virual后，继承以后，在主函数中输出不是动态联编，输出的都是1呢还是，求教！谢谢啊

#include<iostream>
using namespace std;
class A
{
      public:
     virtual int get(){return 1;} //难道不对吗这里？
};
class B:public A
{
      public:
      int get(){return 2;}
};
int main()
{
    while(1)
    {
    cout<<"1:父类2:子类3:退出："<<endl;
    int choice;
    cin>>choice;
    A*p;
    bool quit =false;
    switch(1)
    {
             case 1:p=new A;
             break;
             case 2:p=new B;
             break;
             case 3:quit=true;
             break;
             default:
                     cout<<"请输入1，2，3"<<endl;
             break;
    }
    if(quit==true)
    {
                  break;
    }
    cout<<p->get()<<endl;
}
system("pause");
return 0;
}