Abstract: A Reed-Solomon error-correction coding (ECC) scheme selectively supports two different-length codes to optimize the trade-off between error performance and the amount of disk space required to store protection symbols. The encoder contains two sets of alpha multipliers; part of one set is multiplexed with the other depending on which code is being used. Also, a shift register within the encoder is selectively lengthened or shortened depending on the code. The code pair is selected so that the generator polynomial of the shorter code is a complete divisor of the generator polynomial of the longer code. Thus, one code is a sub-code of the other. Accordingly, the ECC system is able to use the same syndrome calculator for each code. The error-correction decoder uses those syndromes that correspond to the roots of the generator polynomial of the code being used.