Cuál es el objetivo principal de una clave primaria?

What is the output of the following program? #include using namespace std; class bclass { public: void print() const; bclass(int a = 0, int b = 0); //postcondition: x = a; y = b; private: int x; int y; }; class dclass: public bclass { public: void print() const; dclass(int a = 0, int b = 0, int c = 0); //postcondition: x = a; y = b; z = c; private: int z; }; int main() { bclass bobject(2, 3); dclass dobject(3, 5, 8); bobject.print(); cout < < endl; dobject.print(); cout < < endl; return 0 ; } void bclass: : print() const { cout < < x < < " " < < y < < endl; } bclass: : bclass(int a, int b) { x = a; y = b; } void dclass: : print() const { bclass: print(); cout < < " " < < z < < endl; } dclass: : dclass(int a, int b, int c) : bclass(a, b) { z = c; }