#include<iostream>

using namespace std;

class CDog
{
	public:
		//copy constructor
		CDog(CDog oldDog);
		//default and conversion constructor
		CDog(int x = 9);
	private:
		int m_age;
};

CDog::CDog(int x)
{
	m_age = x;
}

CDog::CDog(const CDog& oldDog)
{
	m_age = oldDog.m_age;
}

void main()
{
	CDog dog;
	CDog dog2(dog);
	CDog dog3(4);

	dog3 = dog;//memberwize copy
}