/*
 **************************************************************************
 * Program name : 030_Greater_common_factor (Recursion Version 1.00)      *
 * Author       : Duck Wong                                               *
 * Language     : C / C++                                                 *
 * Compiler     : Boodshed Dec-C++ compiler Ver 3.95                      *
 * Computer     : PII350                                                  *
 * O/S          : Windows 98                                              *
 **************************************************************************
 * Version 1.00 : 2000/06/12 - first version                              *
 **************************************************************************
 * Description  : (a) Input the size of the checkerboard pattern          *
 *                (b) Output the checkerboard pattern                     *
 *                (c) Try again ?                                         *
 **************************************************************************
*/
#include <iostream.h>
#include <stdlib.h>

void gcf(unsigned long N1, unsigned long N2)
{
 if ((N1 % N2) != 0)                                                  // Note(1)
   gcf(N2,N1 % N2);
 else cout << N2;                                                     // Note(2)
}

int main()
{
 // part 1 : declaration
 unsigned long  Num_1, Num_2;
 char  Again;

 do {
     // part 2 : Asking two numbers
     cout << "\nPlease enter 2 integer numbers : ";
     cin  >> Num_1 >> Num_2;

     // part 3 : Calculation and output result
     cout << "\nGCF = ";
     gcf(Num_1,Num_2);
     cout << "\n" << endl;

     // part 4 : try another numbers ?
     cout << "\aTry another set of numbers (Y/N) : ";
     cin  >> Again;
     cout << "\n";
    } while (Again=='Y' || Again=='y');
 cout << "\n" << endl;

 system("PAUSE");
 return 0;
}

/* Notes
   (1) How to find the GCF :

       Example (a)  60 , 12    ->   GCF = 12 since (60 % 12) = 0
               (b)  60 , 48    ->   (60 % 48) = 12 (no equal to zero),
                                    then call the gcf function again with
                                    the new values 48 and 12.
                                    GCF = 12 since (48 % 12) = 0

   (2) Can not use "return" statement.
       Display the value of the GCF directly to the screen.
*/