Half Adder, Full Adder

Half Adder

The Combinational circuit that performs arithmetic addition of two binary digits is called half adder. Variables that are supplied to input of half adder are called augend and addend. The Output obtained is sum and carry. Figure given below shows logical and symbolic representation of  half adder.

Here A and B are two inputs and S, C are sum and Carry respectively.Half Adder is the combination of one XOR gate and one AND gate.
S= A'B +AB'
C=AB

Full Adder

It is the Combinational Circuit that performs addition of three input bits.Three inputs are supplied and result is obtained by two output lines. A and B are operands and C_in is a bit carried in from the next less significant stage.Output is obtained as S,which gives the value of least significant bit of sum, and C_out which gives output carry.

Truth Table is as Follows: