Question

Is it function overloading or overriding or something else ? ( hello function )

class A {

public:
    void hello(int x) { cout << "A" << endl; }

};

class B : public A {

public:
    void hello() { cout << "B" << endl; }

};

void main() {

    B obj;
    obj.hello();

}

Answer 1

It’s neither, it’s function hiding.

Declaring a non-virtual function with the same name (even if the signature is different) in a derived class hides the base class implementation completely.

To still have access to A::hello, you can do the following:

class B : public A {
public:
    using A::hello;
    void hello() { cout << "B" << endl; }
};

Overriding:

struct A
{
   virtual void foo() {}
};
struct B : public A
{
   /*virtual*/ void foo() {}
};

Overloading:

struct A
{
   void foo() {}
   void foo(int) {}
};