It is possible to build memories in which the contents of all registers are tested simultaneously, and in which there is a single indication of the presence or absence of any number of positive responses to the test criterion. A method is described for separately identifying the members of a set of responses by presenting sequences of tests which generate an identification number for each member. The testing algorithm is easily mechanized, and the number of tests required per item is approximately proportional to the logarithm of the number of file registers. The method also may be used to search for items with contents falling within arbitrary numerical ranges.