Sometimes when data is being transferred electronically from one place to another it can become corrupted.

A parity check is used to make sure that data has not been corrupted during transmission.

Data is transmitted as a binary pattern of 0s and 1s.

A parity check involves adding an extra 0 or 1, called a parity bit, to the binary pattern so that the total number of 1s in the pattern is either an even number, this is called even parity, or an odd number, this is called odd parity.

Even Parity

In even parity the parity bit is set to either 0 or 1 so that the total number of 1s adds up to an even number.

In this example there are four 1s so the value 0 is needed in the parity bit to keep the number of 1s even.

Odd Parity 

In odd parity the parity bit is set to either 0 or 1 so that the total number of 1s adds up to an odd number.

In this example there are two 1s so the value 1 is needed in the parity bit to make the number of 1s odd.