Paritetsbitar

Paritetsbitar are a simple form of error-detecting code used in digital communications and storage systems. They add one extra bit to a data block so that the total number of 1 bits in the block has a defined parity, either even or odd. If the receiving system recomputes the parity and finds a mismatch, it signals an error.

There are two common types: even parity and odd parity. In even parity, the parity bit is chosen so that the total number of 1s in the data plus the parity bit is even. In odd parity, the total number of 1s is made odd. To compute the parity bit, count the number of 1s in the data; for even parity, if the count is odd, set the parity bit to 1; for odd parity, if the count is even, set the parity bit to 1.

Usage contexts include serial communications (for example, in some UART configurations), certain data storage schemes, and historical computer memory systems. Paritetsbitar provide a low-cost, simple error-detection mechanism that can reveal most single-bit errors in a block and some multiple-bit errors. However, they cannot correct errors, and they may fail to detect errors that flip an even number of bits or occur in patterns that preserve parity.

Limitations mean parity bits are often supplemented or replaced by more robust schemes such as cyclic redundancy checks (CRC) or error-correcting codes (ECC) in modern systems. Paritetsbitar remain a basic and widely understood concept in the study of data integrity and communication protocols.