What digital circuit is capable of adding or subtracting numbers?

What digital circuit is capable of adding or subtracting numbers?

• A. Adder-Subtractors
• B. Subtractor
• C. Adder
• D. Multiplier

Answer: (A)

When you need to perform either addition or subtraction with binary numbers, you use a circuit that can handle both operations by controlling the second operand and the initial carry. This is an adder-subtractor, essentially an adder with a mode control that can invert the second operand and set the carry-in to implement subtraction. In add mode, it adds A and B normally. In subtract mode, it adds A to the two’s complement of B (invert B and set carry-in to 1), effectively computing A − B. That combination lets one circuit perform both operations efficiently. The other options describe circuits that do only one operation or a different operation altogether (pure addition, pure subtraction, or multiplication), so they don’t fit the requirement of adding or subtracting numbers.

When you need to perform either addition or subtraction with binary numbers, you use a circuit that can handle both operations by controlling the second operand and the initial carry. This is an adder-subtractor, essentially an adder with a mode control that can invert the second operand and set the carry-in to implement subtraction. In add mode, it adds A and B normally. In subtract mode, it adds A to the two’s complement of B (invert B and set carry-in to 1), effectively computing A − B. That combination lets one circuit perform both operations efficiently. The other options describe circuits that do only one operation or a different operation altogether (pure addition, pure subtraction, or multiplication), so they don’t fit the requirement of adding or subtracting numbers.