This module does an bit by bit sum, 2 complement,or,and,xor,and not operation of two 8 bit numbers (not and 2 compliment its just 1 number) It has two shift registers that feed your numbers to the procesing unit with an external load/shift signal and they stop once the registers are empty, the procesing unit then sends your results to one of the 2 registers so you can see the result ther, and the carry out in the carry out output.