Question: (a) Design circuits for half- and full subtractors. The half-subtractor has two inputs and two outputs (DIFFERENCE and BORROW). The full sub-tractor has three inputs (two bits from the current stage and a BORROW-IN from the previous stage) and two outputs (DIFFERENCE and BORROW).
(b) Connect a half-subtractor and three full subtractors to realize the sub-traction circuit for four-bit numbers.