It is a non-member function, but having access to class 
members.

If a class B is derived from A, we can access the data and 
member function of A.So in order to access a class data or 
function from another class we have to derive the class. 
but this can be done by declaring a class as 'friend' and 
can access the another class functions and data.

it is  nonmember function of class it can access the 
private and protected members in the class, And it is 
defined by a keyword frind.........