Half-adder is a simple combinational circuit that can add only two bits together. It is a combination of XOR gate and AND gate where XOR gate is used to perform addition and AND gate is used to get the carry output.
Sum = X XOR Y;
Carry = XY
Half-adder receives two inputs and produces two outputs. The inputs are the two bits to be added and the outputs are sum and carry.
The logic diagram for half-adder has two gates: XOR and AND. The XOR gates produces sum and AND get produces carry. For example if the inputs are 0 and 1 then the output of XOR gate will be the sum, 1 and carry, 0.
The disadvantage is that it will not be useful for adding large binary numbers.