An elementary electronic circuit in the arithmetic logic unit (ALU) of the CPU that adds one bit to another. The output of the half-adder is a result of 0 or 1 and a carry of 0 or 1. All circuits comprise transistors wired together in the form of AND, OR and NOT Boolean logic gates. See binary, Boolean logic and ALU.

**Trace the Circuit Yourself**

BOOLEAN LOGIC GATESGate Input 1 Input 2 OutputAND 1 1 1 AND 0 1 0 AND 1 0 0 AND 0 0 0 OR 1 1 1 OR 0 1 1 OR 1 0 1 OR 0 0 0Gate Input OutputNOT 10 NOT 01

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