pariteettibitin

Pariteettibitti, meaning parity bit in Finnish, is a simple error detection mechanism used in digital communication and data storage. Its purpose is to detect single-bit errors that may occur during transmission or storage.

A parity bit is an extra bit added to a binary message or data word. It is set to either 0 or 1 depending on the number of '1' bits in the original data. There are two common methods for calculating parity: even parity and odd parity. In even parity, the parity bit is set so that the total number of '1' bits in the message, including the parity bit, is an even number. Conversely, in odd parity, the parity bit is set to make the total number of '1' bits an odd number.

For example, if a data word is 1011001 and we are using even parity, there are four '1' bits. To maintain even parity, the parity bit would be 0, as 4 + 0 is even. If the data word were 1011010, with five '1' bits, the parity bit would be 1 to make the total six '1' bits, thus even.

When the data is received or read, the parity is recalculated. If the recalculated parity matches the received parity bit, it is assumed that no error has occurred. If there is a mismatch, it indicates that an error has likely happened during transmission or storage. However, it's important to note that a parity bit can only detect an odd number of bit errors. If an even number of bits are flipped (e.g., two bits), the parity check will still appear correct, and the error will go undetected. Despite this limitation, the simplicity and low overhead of parity bits make them useful in certain applications.