an error correction code for encoding the presence of a special uncorrectable error as well as its type . in the encoder , modification logic modifies the regular data symbols to indicate the type of special uncorrectable error . the encoder appends to the regular data symbols a special uncorrectable error symbol indicating the presence of a special uncorrectable error to form an extended data word , which is encoded to generate a code word . in the decoder , a syndrome generator generates a syndrome vector using an assumed value for the special uncorrectable error symbol indicating the absence of a special uncorrectable error , while a syndrome decoder determines the presence of the special uncorrectable error by determining the presence of an error in the assumed value of the special uncorrectable error symbol . by so using its error detection logic , the decoder makes it unnecessary to actually store or transmit the special uncorrectable error symbol .