Unidirectional Error Codes for Shift-Register Memories

In this correspondence we give an efficient error control technique for mass memories such as magnetic bubble memories, magnetic tapes, etc. The code discussed here is a modification of the cyclic redundancy check (CRC) used in magnetic tape units. An arithmetic redundancy check (ARC) with respect to an appropriate modulus (or check base) replaces the CRC, and the result is a systematic code which provides correction of multiple unidirectional errors in any one track of a large block of characters. The information rate of this code is much higher than that of the CRC code.