In CeePlusPlus, a friend function is a function that a class declares its "friend":

 class Foo {
 private:
 	int heyThatsMine;

 	friend void foosFriend(Foo&);
 };

Functions are permitted to access private members of their friends, which, normally, only members of the same class are allowed to do.

 void foosFriend(Foo& foo) {
 	foo.heyThatsMine = 0; // OK
 }

 void notFoosFriend(Foo& foo) {
 	foo.heyThatsMine = 0; // ERROR: Foo::heyThatsMine is private
 }

Friend function declarations are often used to grant access to private members to OverloadedOperator''''''s.

''When I first saw this page I misread its title as "FriedFunction"...''