Can a copy constructor accept an object of the same class as parameter, instead of reference of the object?

Question

We define copy constructor using
A(const A & obj)

Why reference (&) is needed?
Why we are not allowed to use.

A(const A obj)

Answer 1

No.: a copy constructor accept an object of the same class as parameter, instead of reference of the object

It is specified in the definition of the copy constructor itself. It should generate an error if a programmer specifies a copy constructor with a first argument that is an object and not a reference.

Answer 2

in copy constructor you have to pass the object of same class...((mandatory));

please check the example of copy constructor.

class sample
{
  int a;

  public:
    sample()
    {
        a = 10;
    }

    sample(&obj)
    {
        a = obj.a;
    }

    void show()
    {
        cout<<a;
    }
};

main()
{
  sample o1,o2;
  o1.show();
  o2.show();
}

in both it will print 10 on output screen;