C++ :: How Could Object Access Its Private Data Members From Outside

How does an object access its private data members in copy constructor.

The relevant part of the code: Code: C::C(const C &obj)
{
x = obj.x;
y = obj.y;
}

Normally the object1 called "obj" cannot access its private data members outside. But in this situation it can access. How can it be explained?

Here are the complete code:

Code:
#include <iostream>
using namespace std;
class C{
public:
C(int,int);
C(const C &);

[Code] .....