Abstract: A method for compressing and expanding binary coded alphanumeric information is practiced in conjunction with a memory wherein user transparent, coded bytes are stored at address locations assigned to recognized permutations of the alphanumeric information. Information, stored in a plurality of input registers, is compressed by generating a memory address based upon the input information or using the input information directly as an address, and then determining from the memory whether or not the permutation represented by the information in the input registers is recognized. If recognized, a coded word is read from the memory which is representative of the permutation and is transmitted. Compression of the units of information per units of code used is achieved by reaccessing the memory with an indexed address generated from the contents stored in additional ones of the input registers or by addressing separate memory modules.