Method and apparatus for capability control

A method and apparatus is provided to translate the contents of access registers into information for use in performing addressing functions for multiple virtual address spaces. The access registers represent the full addressing capability of the system but do not directly contain the addressing information. The system has a plurality of general purpose registers (20), a plurality of access registers (22) associated with the general registers, an access list (24,25) having access list entries which is addressed by the contents of the access register, memory storage (30) for holding address space number second table entries (ASTE) (98), where the contents of the access list entry locate the ASTE and where the ASTE contains the addressing information needed to locate a virtual address when combined with the contents of a general register. Access register translation (ART) consists of the process of determining addressing information by using the access list entry and the ASTE. The system has available to it at any one time a selection of one of two domains each represented by an access list. One domain is related to the dispatchable unit task to be performed and the other is related to the address space in which a particular program operates. The ART process selects the domain which the access register is using.