2. The method of claim 1 , further comprising the following step: determining whether the input is a removing function; and removing a stored input value when the input is determined to be the removing function.
2. The method of claim 1 , further comprising the following step: determining whether the input is a removing function; and removing a stored input value when the input is determined to be the removing function. 3. The method of claim 2 , wherein the removed input value is the last stored input value among the stored input values.