In digital logic, what are the outputs produced by a half-adder circuit?
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ASUM
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BCARRY
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CSUM and CARRY
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DDIFFERENCE and BORROW
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EOnly SUM when inputs are equal
Answer
Correct Answer: SUM and CARRY
Explanation
Introduction / Context:The half-adder is the fundamental combinational block for binary addition. It adds two single-bit operands and produces two outputs representing the result in binary form.
Given Data / Assumptions:
- Inputs: single-bit A and B.
- No carry-in (that's why it is called “half”-adder).
Concept / Approach:
The half-adder implements SUM = A ⊕ B and CARRY = A * B. Both outputs are required to represent the full addition result (sum bit and carry-out to the next stage).
Step-by-Step Solution:
Truth table confirms: (A,B) = (0,0) → SUM=0, CARRY=0; (0,1) → 1,0; (1,0) → 1,0; (1,1) → 0,1.Hence outputs are SUM and CARRY.Verification / Alternative check:
Compare with full-adder, which adds A, B, and Cin. A half-adder is the special case with Cin = 0.
Why Other Options Are Wrong:
- Only SUM or only CARRY is incomplete.
- DIFFERENCE and BORROW: that is a half-subtractor's outputs, not a half-adder's.
Common Pitfalls:
Confusing adder and subtractor outputs; forgetting that carry arises only when both inputs are 1.
Final Answer:
SUM and CARRY