RosettaCodeData/Task/Greatest-common-divisor/QuickBASIC/greatest-common-divisor-1.basic

DECLARE FUNCTION gcd (a%, b%)
PRINT gcd(18, 30)
END

FUNCTION gcd (a%, b%)
  WHILE b% <> 0
    t% = b%
    b% = a% MOD b%
    a% = t%
  WEND
  gcd = ABS(a%)
END FUNCTION