Paritykoder

Paritykoder, or parity codes, are a family of simple error-detecting schemes used in data transmission and storage. They work by appending a parity bit to a data unit (such as a byte or a word) so that the total number of 1 bits conforms to a predefined parity, typically even or odd.

With even parity, the parity bit is chosen so that the total count of 1s is even; with odd parity, the total is odd. When the data is read or received, the system recomputes the parity; a mismatch signals that one or more bits have flipped during transmission or storage.

Parity codes are inexpensive and easy to implement in hardware or software, making them common in simple serial interfaces and some memory systems. However, they have limitations: they can usually detect only single-bit errors and cannot correct errors; a two-bit error that preserves the chosen parity may go undetected. For stronger protection, systems rely on more advanced methods such as cyclic redundancy checks (CRC) for detection or error-correcting codes (ECC) such as Hamming or BCH that can locate and correct errors.

Variants include two-dimensional parity, which adds parity bits for both rows and columns, enabling the location of some single- and multi-bit errors. Parity concepts are foundational in coding theory and serve as building blocks for more sophisticated codes used in modern storage and communications.