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.

Abstract: A plurality of peripheral devices having physical addresses are accessed by a host processor by use of logical addresses which are utilized by the various programs in a multiprocessing environment. Input/output tables are arranged to include pointers for relating the logical address provided by a programmer to the physical address of the device thereby providing necessary device specific information to the peripheral controller coupled with the peripheral devices. The input/output tables are structured so that pointers relating the physical and logical addresses may be changed to reassign the logically addressed device to another device and accordingly to point to another physical address.