Unidirectional 9-bit byte error detecting codes for computer memory systems

Codes are developed for detecting unidirectional errors in t bytes simultaneously (t-UBED). Some of the codes constructed also provide all unidirectional error detection (AUED). These classes of codes are different from AUED codes in that the errors in one byte may be of the form 1 to 0 while in another byte they may be of the form 0 to 1. The codes developed are for bytes of length nine consisting of eight data bits and one parity bit and utilize one byte for parity check information in addition to the parity check bits. Under various assumptions, codes varying in protection from 2-UBED to 4-UBED and 2-UBED+AUED to 3-UBED+AUED are constructed.<>