A Level Computer Science OCR Practice Exam

What does a Full Adder produce as a result of its operation?

1. Only a sum bit

2. Only a carry-out bit

3. A sum bit and a carry-out bit

4. A stored bit

The correct answer is: A sum bit and a carry-out bit

A Full Adder is a digital circuit that performs the arithmetic operation of addition on three binary inputs, specifically two significant bits and a carry bit that comes from a less significant position. The Full Adder takes in these three inputs to produce two outputs: the sum and the carry-out. The sum bit represents the result of adding the two bits together along with any carry-in, providing a single binary digit result. Meanwhile, the carry-out bit is vital for multi-bit binary addition since it indicates whether there is an overflow from the addition of the two bits that needs to be carried over to the next higher bit position. By producing both a sum bit and a carry-out bit, the Full Adder enables the construction of more complex arithmetic circuits, including multi-bit adders that can handle larger numbers through cascading multiple Full Adders together. This combination of outputs is essential for accurate binary computation.