The adder array contains the 8-bit ripple carry adder and various t-gates. The addsub cell,as it is called in the cell hierarchy, has two 8-bit numbers input as well as several control signals. The FSM can select between either passing the inputs straight to the adder, inverting one or both, or inputing a zero as the lower (b) input. The inversions are for subtraction and divison, and the zero input is for multiplication.