11.1.1.1 ABS Function
  The ABS function returns a floating-point number that
  equals the absolute value of a specified numeric expression.
  For example:
  READ A,B
  DATA 10,-35.3
  NEW_A = ABS(A)
  PRINT NEW_A; ABS(B)
  END

  Output
    10 35.3
  The ABS function always returns a number of the default
  floating-point data type.