PROGRAM 21


PROGRAM FINDGCD_OF_3_INTEGERS;
        {ANTHONY F. ORITZ, ASSIGNMENT 7A, JULY 14, 1994}
        {THIS PROGRAM FINDS AND PRINTS THE GCD OF THREE FACTORS.}

USES CRT;

VAR
   A, B, C, GCD, GCD2:  INTEGER;
                  ANS:  STRING;

PROCEDURE INPUTDATA (VAR A, B, C:  INTEGER);

BEGIN
     WRITE ('ENTER THE FIRST POSITIVE INTEGER.  ');
     READLN (A);
     WRITE ('ENTER THE SECOND POSITIVE INTEGER. ');
     READLN (B);
     WRITE ('ENTER THE THIRD POSITIVE INTEGER.  ');
     READLN (C);
END;

PROCEDURE ABSOLUTEVALUE;

BEGIN
     A := ABS (A);
     B := ABS (B);
     C := ABS (C);
END;

PROCEDURE PRINTRESULTS;

BEGIN
     WRITELN;
     IF (A <> 0) AND (B <> 0) AND (C <> 0) THEN
        WRITELN ('THE GCD OF ',A, ', ',B, ', AND ', C, ' IS ', GCD2, '.');
     WRITELN;
END;

PROCEDURE INQUIRY;

BEGIN
     WRITE ('WOULD YOU LIKE TO CONTINUE WITH THIS PROGRAM?  TYPE "YES" TO CONTINUE. ');
     READLN (ANS);
END;

FUNCTION FINDGCD (A, B:  INTEGER):  INTEGER;

BEGIN
     IF (A = 0) OR (B = 0) THEN
        BEGIN
             GOTOXY (1, 4);
             WRITELN;
             GOTOXY (1, 5);
             WRITE ('THESE THREE VARIABLES DON''T HAVE A GCD. ');
        END
     ELSE
        BEGIN
             WHILE A <> B DO
             IF A > B THEN
                A := A  - B
             ELSE
                B := B - A;
        END;
     FINDGCD := A;
END;

BEGIN
     REPEAT
           CLRSCR;
           INPUTDATA (A, B, C);
           ABSOLUTEVALUE;
           GCD := FINDGCD (A, B);
           GCD2 := FINDGCD (GCD, C);
           PRINTRESULTS;
           INQUIRY;
     UNTIL ANS <> 'YES';
END.

{  OUTFILE:  PROG21.OUT  }

ENTER THE FIRST POSITIVE INTEGER.  2
ENTER THE SECOND POSITIVE INTEGER. 4
ENTER THE THIRD POSITIVE INTEGER.  6

THE GCD OF 2, 4, AND 6 IS 2.

WOULD YOU LIKE TO CONTINUE WITH THIS PROGRAM?  TYPE "YES" TO CONTINUE. no




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