When you use multiple inheritance, you may create 

class A {
public:
    int number = 10;
};

class B : public A {};
class C : public A {};

class D : public B, public C {};

int main() {
    D obj;
    // obj.number  // ❌ ERROR – which A?
}


class A {
public:
    int number;
    A() { number = 10; }
};

class B : public virtual A {};
class C : public virtual A {};

class D : public B, public C {};

int main() {
    D obj;
    cout << obj.number;
}


class Shape {
protected:
    float dimension;
public:
    void getDimension() {
        cin >> dimension;
    }
    virtual float calculateArea() = 0;  // pure virtual
};

class Square : public Shape {
public:
    float calculateArea() {
        return dimension * dimension;
    }
};

class Circle : public Shape {
public:
    float calculateArea() {
        return 3.14 * dimension * dimension;
    }
};


Square s;
s.getDimension();
cout << s.calculateArea();


When an object of child class is created:

class Parent {
public:
    Parent() {
        cout << "Inside Base Class\n";
    }
};

class Child : public Parent {
public:
    Child() {
        cout << "Inside Child Class\n";
    }
};

int main() {
    Child obj;
}


class Outer {
public:
    class Inner {
        int x;
    public:
        void set(int v) { x = v; }
        void show() { cout << x; }
    };
};

int main() {
    Outer::Inner obj;   // scope resolution
    obj.set(100);
    obj.show();
}


⚠ Inner class can access ONLY static members of outer class.

class Outer {
public:
    int a = 10;
    static int b;

    class Inner {
    public:
        void show() {
            // cout << a;   ❌ cannot access non-static
            cout << b;      // ✔ can access static
        }
    };
};

int Outer::b = 20;


ClassName *ptr;
ptr = &object;
ptr->memberFunction();


class MyClass {
    int num;
public:
    void setNumber(int value) { num = value; }
    void showNumber() { cout << num << endl; }
};

int main() {
    MyClass obj, *p;

    obj.setNumber(100);
    obj.showNumber();

    p = &obj;
    p->showNumber(); // pointer access
}
