这里面高手主要看一下MAIN函数就知道为什么出错了，可是我还是不知道，帮我看看，谢谢了。
#include <iostream>
using namespace std;
class person
{
public:
virtual void work();
person(){cout<<"执行Person"<<endl;}
};
void person::work()
{
cout<<"个人"<<endl;
}
class doctor:public person
{
public:
void work();
doctor()
{cout<<"执行doctor"<<endl;}
};
void doctor::work()
{
cout<<"医生"<<endl;
}
class teacher:public person
{
public:
void work();
teacher(){cout<<"执行teacher"<<endl;}
};
void teacher::work()
{
cout<<"教师"<<endl;
}
class student:public person
{
public:
void work();
student(){cout<<"执行student"<<endl;}
};
void student::work()
{
cout<<"学生"<<endl;
}
int main()
{
person a;
doctor b;
teacher c;
student d;
person *p=&a;
a->work();
return 0;
}