Наследование_2

//classes.h

#ifndef C1_H
#define C1_H

class C1
{
public:
       C1();
       C1(int a);
protected:
       int x;
};


//********************


class C2:public C1
{
public:
       C2();
       C2(int b);
};



//********************

class C3:public C2
{
public:
       C3(int c);
};
#endif

_______________________________________

classes.cpp

#include <iostream>
#include "classes.h"

C1::C1()
{
std::cout<<"Constructor 1_1"<<std::endl;
x=10;
}

C1::C1(int a)
{
std::cout<<"Constructor 1_2"<<std::endl;
x=a;
}

C2::C2()
{
std::cout<<"Constructor 2_1"<<std::endl;
x=12;
}

C2::C2(int b)
{
std::cout<<"Constructor 2_2"<<std::endl;
x=b;
}

C3::C3(int c)
{
std::cout<<"Constructor 3"<<std::endl;
x=c;
}

_______________________________

main.cpp

#include "classes.h"
#include <iostream>

int main()
{
    int a = 20;
    int b = 30;
    int c = 40;

    C1 obj1_1;
    C1 obj1_2(a);

    C2 obj2_1;
    C2 obj2_2(b);

    C3 obj3_2(c);

    std::cin.sync();
    std::cin.get();
    return 0;
}