5 REM find greatest common divisor (Euclidean Algorithm)
   10 CALL SHELL("cls")
   20 LET A = 1071
    : LET B = 462
   30 IF A < B THEN
    :   C = A
    :   A=B
    :   B=C
    : END IF
   40 PRINT A,B
   50 LET C = A - INT(A/B)*B
    : REM C = A MOD B (A modulo B)
   60 LET A = B
    : B = C
   70 IF B > 0 GOTO 40
   80 PRINT "GCG is ";A
   90 END