Full adder
Combinational circuit adding two bits and carry-in producing sum and carry-out. Full adders cascade for multi-bit arithmetic. Fundamental CPU component.
Formula
Sum = A XOR B XOR Cin; Cout = (A AND B) OR (Cin AND (A XOR B))
Real World
When a PlayStation 5's CPU adds two 64-bit numbers to calculate physics in a game, it chains 64 full adders in a ripple-carry arrangement, each passing its carry-out to the next stage.
Exam Focus
Clearly distinguish full adder from half adder by emphasising the carry-in input — this is the most common lost mark.
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