• Source 
    1. #include <iostream>
    2. using namespace std;
    3.  
    4. class A {
    5. 	private :
    6. 		int x;
    7. 	public  :
    8. 		A () {
    9. 			cout << "I anyway use parameter-less constructors, they are called always" << endl;
    10. 		}
    11. 		A (const int& x) {
    12. 			this->x = x;
    13. 			cout << "I can use the parent constructor" << endl;
    14. 		}
    15. };
    16.  
    17. class B : public A {
    18. 	private :
    19. 		int y;
    20. 	public  :
    21. 		B() {
    22.  
    23. 		}
    24. 		B (const int& x, const int& y) : A (x) {
    25. 			this->y = y;
    26. 		}
    27. };
    28.  
    29. int main() {
    30.  
    31. 	B* b  = new B(1,2);
    32. 	B* b1 = new B();
    33. 	return 0;
    34. }