A new class of symmetric error correcting/unidirectional error detecting codes

A new class of t-error correcting/all or d (d>t) unidirectional error-detecting (UED) code is developed. Such codes can correct symmetric errors in the information part of the codeword. When the added checkbits also have symmetric errors, the errors are detected. Furthermore, (t+1) or more unidirectional errors can be detected by the t-IEC (information error correcting)/A-UED code, while unidirectional errors in (t+1) or more but d or fewer bits can be detected by the t-IEC/d-UED code. By giving up the capability of correcting symmetric errors in the added checkbits a very substantial saving in the length of the codeword is obtained. Such codes can offer protection against transient as well as permanent faults