Paritätsbitcode

Paritätsbitcode, or parity bit coding, is one of the simplest forms of error-detecting codes used in digital communication and storage. In this scheme, a parity bit is appended to a block of data so that the total number of 1 bits follows a predefined parity, typically even or odd. The parity bit is computed as the modulo-2 sum (XOR) of the data bits. In an even-parity system, the parity bit is chosen so that the total number of 1s is even; in an odd-parity system, the total is odd.

Typically the parity bit is added per data unit, such as per byte or per word, and transmitted or stored alongside the data. If a single bit flips during transmission or storage, the parity check detects the error; if an even number of bits flip, the error may go undetected.

Advantages of parity bit coding include its simplicity and very low overhead—one extra bit for every set of data bits. Its main limitation is that it cannot locate or correct errors, and it is unable to reliably detect certain error patterns, especially even numbers of bit flips or burst errors. For more robust error handling, parity is often combined with additional techniques such as two-dimensional parity, Hamming codes, or cyclic redundancy checks (CRCs).

Variants include even parity and odd parity, as well as extended schemes like two-dimensional parity, which add parity checks for both rows and columns to improve detectability of multiple bit errors. Paritätsbitcode remains a foundational, lightweight method for basic error detection in legacy and simple systems.