The term usually applies to a single parity bit per bit stream, although it could also be used to refer to a larger Hamming code. While simple longitudinal parity can only detect errors, it can be combined with additional error control coding, such as a transverse redundancy check, to correct errors.
A longitudinal redundancy check for a sequence of characters may be computed in software by the following algorithm:
Set LRC = 0
For each character c in the string
Set LRC = LRC XOR c
An 8-bit LRC such as this is equivalent to a cyclic redundancy check using the polynomial x8+1, but the independence of the bit streams is less clear when looked at that way.