# Some Computer Hardware Devices

**ADDER:- **Adder is a combinational Circuit use which is use to add bits. In computer we use two types of adder:

1) Half Adder

2) Full Adder

**Half Adder:-** The **half adder** adds two single binary digits *A* and *B*. It has two outputs, sum (*S*) and carry (*C*). The carry signal represents an overflow into the next digit of a multi-digit addition. The value of the sum is 2*C* + *S*. The simplest half-adder design, pictured on the right, incorporates an XOR gate for *S* and an AND gate for *C*. With the addition of an OR gate to combine their carry outputs, two half adders can be combined to make a full adder.

**Full Adder:-** A **full adder** adds binary numbers and accounts for values carried in as well as out. A one-bit full adder adds three one-bit numbers, often written as *A*, *B*, and *C*_{in}; *A* and *B* are the operands, and *C*_{in} is a bit carried in from the next less significant stage The full-adder is usually a component in a cascade of adders, which add 8, 16, 32, etc. binary numbers. The circuit produces a two-bit output sum typically represented by the signals *C*_{out} and *S*, where . The one-bit full adder's truth tableis: