Universal college of engineering & technology

.By Harsh Patel)

What is Adder?

Adder : In electronics an adder is digital circuit that perform addition of numbers. In modern computer adder reside in the arithmetic logic unit (ALU).

Adders : Adders are important not only in the computer but also in many types of digital systems in which the numeric data are processed. Types of adder: 1. Half adder 2. Full adder

Half adder : The half adder accepts two binary digits on its inputs and produce two binary digits outputs, a sum bit and a carry bit.

Full adder : The full adder accepts two inputs bits and an input carry and generates a sum output and an output carry.

Truth Table of Adder ABC in C out ∑

A B C in ∑ C out C out = (A B). C in + A.B Circuit of Adder

4-Bit Adder  A single full –adder is capable of adding two 1-bit numbers and input carry.  What happens if we want to add binary numbers with more than 1-bit?  The concept of additional full-adders must be used i.e. to add 2-bit numbers two adders must be needed and to add 4-bit numbers four adders must be needed.

4-Bit Adder

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