Abstract: For reducing the redundancy ratio of an entity key set, from very high ratios when encoded into conventional I/O code-words, down to a ratio close to zero, a non-redundant number code representation is employed in an encoder/decoder in lieu of a conventional multiple code-word representation, each member of the number code representing a member of the entity key set. Such a number code encoder/decoder may hold in store and provide access to an entity key set representing a set of 65535 different textual or lexical words, thereby using a 16 bit fixed length number code. Code-words representing such code numbers would require 16 bits of storage each if being held in store, however, such code numbers are produced using two alternative methods, (i) as relative address values of individual storage locations within a string of storage locations, e.g., a string of 8 bit byte locations, or (ii) as marked bit counts within a bit map representing the stored set.