A simple error detection method that operates on some set of information (usually data or program). If this information is in units that are m bits wide, a sum is taken modulo n, where n = 2m, and appended to the information. At a later time or different location the check may be recomputed and most simple (all single) bit errors will be detected. A parity check is the simplest version of this check with m = 1 and n = 2.