Class pointer usage

clas_by_point.cpp

#include <iostream>

class A {
private:
    int valueA;
public:
    A():valueA(1) {
    }
    int getValueA() {
        return this->valueA;
    }
};

class B : public A {
private:
    int valueB;
public:
    B():valueB(2) {
    }
    int getValueB() {
        return this->valueB;
    }
};

class C : public B {
private:
    int valueC;
public:
    C():valueC(3) {
    }
    int getValueC() {
        return this->valueC;
    }
};

int main(int argc, const char * argv[]) {
    A *a = new A;
    B *b = new B;
    C *c = new C;
    std::cout << a->getValueA() << std::endl;    // 1
    std::cout << b->getValueA() << std::endl;    // 1
    std::cout << c->getValueA() << std::endl;    // 1
    
    A aa;
    B bb;
    C cc;
    std::cout << aa.getValueA() << std::endl;    // 1
    std::cout << bb.getValueA() << std::endl;    // 1
    std::cout << cc.getValueA() << std::endl;    // 1
    return 0;
}