Editing Parity bit (section)

== History ==
A ''parity track'' was present on the first [[magnetic-tape data storage]] in 1951. Parity in this form, applied across multiple parallel signals, is known as a [[transverse redundancy check]]. This can be combined with parity computed over multiple bits sent on a single signal, a [[longitudinal redundancy check]]. In a parallel bus, there is one longitudinal redundancy check bit per parallel signal.

Parity was also used on at least some paper-tape ([[punched tape]]) data entry systems (which preceded magnetic-tape systems). On the systems sold by British company ICL (formerly ICT) the {{convert|1|in|mm|adj=mid|-wide}} paper tape had 8 hole positions running across it, with the 8th being for parity. 7 positions were used for the data, e.g., 7-bit ASCII. The 8th position had a hole punched in it depending on the number of data holes punched.