What Does 'Parity Check' Mean?

“Parity check” is a method of checking the accuracy of data transmission or storage. It involves adding an extra bit, called a parity bit, to the data being transmitted or stored in order to make the total number of 1s either even or odd. This allows the receiver or reader of the data to detect any errors that may have occurred during transmission or storage.

There are two categories of parity checks: even parity and odd parity. In even parity, the parity bit is set to 1 if the total number of 1s in the data being transmitted is odd, and it is set to 0 if the total number of 1s is even. In odd parity, the parity bit is set to 0 if the total number of 1s in the data is odd, and it is set to 1 if the total number of 1s is even.

For example, consider a data transmission that consists of four bits: 1001. If even parity is being used, the parity bit would be set to 1, because the total number of 1s in the data (1) is odd. The complete transmission would then be 10011. When using odd parity, the parity bit is set to 0 because the total number of 1s in the data is odd. The complete transmission would then be 10010.

When the data is received or read, the parity bit is checked to ensure that it matches the parity of the data. If the parity bit does not match the data, it is an indication that an error has occurred during transmission or storage. The receiver or reader can then request a retransmission of the data or take other appropriate action to correct the error.

“Parity check” is a simple and effective method for detecting errors in data transmission or storage, but it is not foolproof. It is possible for errors to go undetected if the data and parity bit are both changed in the same way, resulting in the same parity as the original data. More advanced error-detection methods, such as the cyclic redundancy check (CRC) and checksum, are often used to provide more reliable error detection.