In maths, parity determines whether a number is even or odd. A parity bit is a type of check digit, or a digit computed from the other digits and appended to end of a datum. To validate the datum, the computer system computes the expected check digit and checks it against the actual check digit. If the two are different, there is an error in transmission. ISBNs are a common application of check digits.
Parity bits are useful for the transmission of bits, e.g. transferring data from the hard disc to the RAM and vice versa. Even parity bits and odd parity bits are two types of parity bits.
We add an even parity bit to the end of a datum to make the number of 1s even. If the original number of 1s is even, the even parity bit is 0; if the original number of 0s is odd, the even parity bit is 1. Odd parity bits simply take the opposite course. If the original number of 1s is even, the even parity bit is 1; if the original number of 0s is odd, the even parity bit is 0.
Exhibit A can evaluate the parity bit of a binary string, while Exhibit B checks a parity-checked string for errors.
Exhibit A: String w/o parity bit:
Exhibit B: String with partiy bit: