Capability-Based Addressing Various addressing schemes making use of segment tables are examined. The inadequacies of these schemes when dealing with shared addresses are explained. These inadequacies are traced to the lack of an efficient absolute address for objects in these systems. The direct use of a capability as an address is shown to overcome these difficulties because it provides the needed absolute address. Implementation of capability-based addressing is discussed. It is predicted that the use of tags to identify capabilities will dominate. A hardware address translation scheme which never requires the modification of the representation of capabilities is suggested. The scheme uses a main memory hash table for obtaining a segment's location in main memory given its unique code. The hash table is avoided for recently accessed segments by means of a set of associative registers. A computer using capability-based addressing may be substantially superior to present systems on the basis of protection, simplicity of programming conventions, and efficient implementation. CACM July, 1974 Fabry, R. S. addressing, capabilities, addressing hardware, protection, protection hardware, shared addresses, information sharing, operating systems, computer utility, segmentation, tagged architecture 4.30 4.32 4.34 6.21 CA740706 JB January 17, 1978 12:39 PM 1458 4 2625 1523 4 2625 1603 4 2625 1698 4 2625 1747 4 2625 1748 4 2625 1854 4 2625 1877 4 2625 1960 4 2625 2317 4 2625 2358 4 2625 2377 4 2625 2377 4 2625 2378 4 2625 2497 4 2625 2558 4 2625 2625 4 2625 2625 4 2625 2625 4 2625 2625 4 2625 2626 4 2625 2632 4 2625 2669 4 2625 2840 4 2625 2922 4 2625 2941 4 2625 3081 4 2625 3101 4 2625 3105 4 2625 3112 4 2625 3144 4 2625 1471 5 2625 1753 5 2625 2358 5 2625 2438 5 2625 2625 5 2625 2625 5 2625 2625 5 2625 2626 5 2625 2868 5 2625 3105 5 2625 3144 5 2625 1471 6 2625 1471 6 2625 1746 6 2625 2080 6 2625 2298 6 2625 2358 6 2625 2377 6 2625 2377 6 2625 2380 6 2625 2491 6 2625 2558 6 2625 2597 6 2625 2624 6 2625 2625 6 2625 2625 6 2625 2625 6 2625 2625 6 2625 2629 6 2625 2632 6 2625 2632 6 2625 2632 6 2625 2868 6 2625 2939 6 2625 3068 6 2625