Question

class C1 {
    void A();
    void B();
}

void C1::A(){ return B(); }

class C2 : public C1 {
    void B();
}

C2 *obj = new C2;
obj->A(); // returns B() from C1

Why does B() from C1 called? How to make A() exist only in C1 and call B() from C2?

Answer 1

You need to make B() in C1 a virtual function.

Virtual functions are basically function pointers that take their value upon initialization of the object. If you new C1, the function pointer would point to C1::B while if you new C2 that function pointer would point to C2::B.

Note: To read more about virtual and related subjects, search for function overriding and polymorphism.