Appendix A: error detection and correction in digital transmissions
From the very first digital data transmissions, the need to detect and, as far as possible, to correct errors introduced by the transmission link has been recognized. Various more or less complex solutions are used, depending on the characteristics of the link, but they invariably consist of adding a calculated redundancy to the original message.
A1.1 An error detecting code: the parity bit
The simplest means of detecting errors is the parity bit; it is still employed in short distance serial transmissions (for instance RS232), where it usually applies to words of 6–8 bits. On the transmission side, all the bits of the word to be transmitted are summed, and a supplementary ...