The Unsigned Integer parameter type is equivalent to Integer—i.e., allows any type except X—although the most natural fit would be data type B. The only point in distinguishing between Integer and Unsigned Integer is to let you know that negative values need not be considered. Note that if you use type I to store an unsigned integer, the range is effectively cut in half; for example, the range of I2 is -32767 to 32767, only half of which is unsigned.