Half Adder : The addition of 2 bits is done using a combination circuit called Half adder. The input variables are augend and addend bits and output variables are sum & carry bits. A and B are the two input bits.

Full Adder Circuit : Full Adder is the adder which adds three inputs and produces two outputs. The first two inputs are A and B and the third input is an input carry as C-IN. The output carry is designated as C-OUT and the normal output is designated as S which is SUM.