C++ Programming - Functions - Discussion

#include<iostream.h> 
class Base
{
    public:
    char S, A, M; 
    Base(char x, char y)
    {
        S = y - y;
        A = x + x; 
        M = x * x;
    }
    Base(char, char y = 'A', char z = 'B')
    {
        S = y;
        A = y + 1 - 1; 
        M = z - 1;
    }
    void Display(void)
    {
        cout<< S << " " << A << " " << M << endl;
    }
};
class Derived : public Base
{
    char x, y, z; 
    public:
    Derived(char xx = 65, char yy = 66, char zz = 65): Base(x)
    {
        x = xx; 
        y = yy;
        z = zz;
    }
    void Display(int n)
    {
        if(n)
            Base::Display(); 
        else
            cout<< x << " " << y << " " << z << endl; 
    }
};
int main()
{
    Derived objDev; 
    objDev.Display(0-1); 
    return 0;
}