基类与派生类的指针问题

#include<iostream>
using namespace std;

class BaseClass
{
public:
    virtual void fn1();
    void fn2();

};

void BaseClass::fn1()
{
    cout<<"调用基类的虚函数fn1()"<<endl;
}

void BaseClass::fn2()
{
    cout<<"调用基类的非虚函数fn2()"<<endl;
}
class DerivedClass
{
public:
    void fn1();
    void fn2();
};

void DerivedClass::fn1()
{
    cout<<"调用派生类的函数fn1()"<<endl;
}

void DerivedClass::fn2()
{
    cout<<"调用派生类的函数fn2()"<<endl;
}

int main()
{
    DerivedClass aDerivedClass;
    DerivedClass *pDerivedClass=&aDerivedClass;
    BaseClass *pBaseClass=&aDerivedClass;//BaseClass *pBaseClass=pDerivedClass;
    pBaseClass->fn1();
    pBaseClass->fn2();
    pDerivedClass->fn1();
    pDerivedClass->fn2();
    return 0;

}