### How Half Adder Works?

How does Half Adder work with the truth table? Half Adder is a combinational logic circuit that adds two binary digits i.e 0 and 1.Combinational circuits are half adder and full adder, subtractor, encoder, decoder, multiplexer, and demultiplexer.

#### What is Combinational Logic Circuits

- The output of a combinational circuit at any instant of time depends only on the levels present at input terminals.
- The combinational circuit does not use any memory. The previous state of input does not have any effect on the present state of the circuit.
- A combinational circuit can have an n number of inputs and an n number of outputs.

The block diagram is shown below in which A and B two inputs and S(Sum) and C(Carry) are outputs.

- Half Adder is a combinational logic circuit.
- It is used for the purpose of adding two single-bit numbers.
- It contains 2 inputs and 2 outputs (sum and carry).

Keep in mind Half Adder is Combinational logic circuit whose output at any instant in time depends only on the *combination* of its inputs. Unlike Sequential Logic *Circuits* whose outputs are dependent on both their present inputs and their previous output state giving them some form of Memory.

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

### How Full Adder Works?

There are two inputs and two outputs in a Half Adder. Inputs are named as A and B, and the outputs are named as Sum (S) and Carry (C). The Sum is X-OR of the input A and B. Carry is AND of the input A and B. With the help of a half adder, one can design a circuit that is capable of performing simple addition with the help of logic gates.

As shown in the above circuit diagram there are two gates that are used X-OR and AND Gate. X-OR gate generates Sum output and AND Gate gives Carry output. In the above diagram, A input connected both X-OR gate and AND Gate. While B input connected both X-OR Gate and AND Gate.

Now a days every electronics circuits use Adders. because most circuits like laptop, LCD TV, mobiles and other electronics equipment’s use adders.

- Above is the truth table of half adder in which we can see that if A and B inputs are zeros SUM and CARRY both are zeros.

- When A is 0 and B is 1 then Sum is 1 and Carry is 0.

- When A is 1 and B is 0 then Sum gives 1 output and Carry gives 0 output.

- When both A and B both inputs are 0s then Sum gives 0 and Carry gives 1 output.