Half adder
Combinational circuit adding two single bits producing sum and carry. Half adder is basic arithmetic circuit building block. Cannot handle carry-in from previous stage.
Formula
Sum = A XOR B; Carry = A AND B
Real World
Inside every smartphone's processor, billions of half adders work together to perform the basic binary additions needed when you tap the calculator app to split a restaurant bill.
Exam Focus
Draw the truth table with all four input combinations — examiners award marks for complete, correctly labelled tables.
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