C++ friend classes

#include <iostream>
using namespace std;
class alpha//from  w  w w .  j  av  a  2s .c o m
{
   private:
   int data1;
   public:
   alpha() : data1(99) {  }   //constructor
   friend class beta;         //beta is a friend class
};
class beta
{                             //all member functions can
    public:                       //access private alpha data
    void func1(alpha a)  { cout << "\ndata1=" << a.data1; }
    void func2(alpha a)  { cout << "\ndata1=" << a.data1; }
};
int main()
{
    alpha a;
    beta b;
    b.func1(a);
    b.func2(a);
    cout << endl;
    return 0;
}