Question

class BaseClass
{
    virtual void g()
    {
        cout<<"BaseClass:g()"<<endl;
    }
private:
    virtual void f()
    {
        cout<<"BaseClass:f()"<<endl;
    }
};

class DeriveClass:public BaseClass
{
    virtual void g()
    {
        cout<<"DeriveClass:g()"<<endl;
    }
private:
    virtual void h()
    {
        cout<<"DeriveClass:h()"<<endl;
    }
};


typedef void (*Fun)(void) ;
int _tmain(int argc, _TCHAR* argv[])
{
    DeriveClass b;
    Fun pFun;
    for(int i = 0; i<3; ++i)//why the variable is 3?
    {
        pFun = (Fun)*((int*)*(int*)(&b)+i);// I don't know this?
        pFun();
    }
    system("pause");
    return 0;
}

Answer 1

This is a question to see if you understand about VTABLEs.

This tutorial http://www.learncpp.com/cpp-tutorial/125-the-virtual-table/ not only uses this example code but explains the answer.