It is possible, when sending data, to send extra information in order to help the destination PC decide whether or not an error has occurred. The code will be used to detect if an error has occurred within the binary data sent. The most basic code is known as parity checks. A parity check will count the number of 1's it the binary string then append an extra bit on the end to say if it has seen an odd number of 1's or a even number of 1's.

Parity of messages could be both odd or even. If even parity is chosen then the number of 1's should always be even. So if in our data bits we had an odd number of 1's, we would add a 1 in the parity bit in order to make it have a even number of 1's.