Abstract: Resources in a data processing system's memory are allocated to a plurality of programs based upon their activity level. The least active programs in the system have their memory space deallocated in favor of new programs which are required during the operation of the system. Each use of a program, whether it be a new program or one which has been used before and is still in the system's memory, causes the activity queue of the used program to be given the highest activity state and further, the activity queues, including queue and link pointers, of the programs next more recently used and next less recently used and the just used program have their activity queues updated. For increased speed in searching for and thereby finding a particular program in response to a received instruction, the programs are linked in families which are depicted by common and significant information bits.