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. Additional circuits shift the operation to the next binary digit on the left until the entire number has been added. For the history of digital circuits, see integrated circuit.

**AND, OR and NOT**

All circuits comprise transistors wired together in the form of Boolean logic gates. Following are the rules for their operation. All the gates have one output. Both AND and OR have two inputs while NOT has only one. See binary, Boolean logic and ALU.

**Trace the Circuit Yourself**

All circuits comprise transistors wired together in the form of Boolean logic gates. Following are the rules for their operation. All the gates have one output. Both AND and OR have two inputs while NOT has only one. See binary, Boolean logic and ALU.

BOOLEAN LOGIC GATESGate Input 1 Input 2 Output(Both inputs must be present) AND 1 1 1 AND 0 1 0 AND 1 0 0 AND 0 0 0 (Only one input is required) OR 1 1 1 OR 0 1 1 OR 1 0 1 OR 0 0 0Gate Input Output(Output is the reverse of the input) NOT 10 NOT 01

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