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Monday, September 1, 2008

Error detection & correction by Parity Checking

In parity checking an extra bit called a parity bit is added to a byte of data or more appropriately a data set to detect if data set is transmitted correctly. This is a means of error detection and sometimes error correction. Parity bit is sometimes also called check bit.

Key points to remember about parity checking

What is added: parity bit(s)/check bit(s)

Where added: to each byte or data unit

Purpose: to detect error in transmission if any or to detect the correctness of data transmitted

Scope: transmission control or data file control.

Types of parity:

  1. vertical parity – single character

  2. horizontal parity – multiple character

Both parity together can not only detect but correct errors as well.

How parity bit for each data unit is set?

The parity bit for each unit is set in such a way so that all bytes have either an even number or an odd number of bits.

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