Parity

Generally parity can be defined as a functional equality. In mathematics it refers to the even or odd quality of a number. If a pair of numbers are both odd or even then they are said to have parity. In computers and data transfer parity refers to a technique of checking whether data has been lost or altered when it’s moved from one place in storage to another. Basically a process is applied to data elements that produces another data element known as a parity element – sometimes referred to as a parity bit. A simple form of parity, for example, counts the number of data bits in a group of data. If the number is even then a parity bit is set on, if it’s an odd number the parity bit stays off. This can be used to quickly tell a system whether data has arrived in tact. The system counts the bits, and if the count agrees with the status of the parity bit it can be assumed the data is in tact. There are much more complex forms of parity that can give much more detailed information about the integrity of data. Many forms of parity are actually structured in such a way as to allow limited amounts of data to be reconstructed if it is lost or corrupted.