Abstract: Computer data and procedure protection by preventing processes from intering with each other or sharing each other's address space in an unauthorized manner is accomplished in hardware/firmware by restricting addressability to a segmented memory and by a ring protection mechanism.To protect information in segments shared by several processes from misuse by one of these processes a ring protection hardware system is utilized. There are four ring classes numbered 0 through 3. Each ring represents a level of system privilege with level 0 (the innermost ring) having the most privilege and level 3 (the outermost ring) the least. Every procedure in the system has a minimum and a maximum execute ring number assigned to it which specifies who may legally call the procedure. Also maximum write and read ring numbers specify the maximum ring numbers for which a write and/or read operation is permitted.

Abstract: A multiprogrammable/multiprocessing digital computer system having a process control block for each process in the system, wherein each process control block includes information which specifies the state of a processor at any given time. Associated with each process control block is a decor extension table having information to indicate whether a specified function, such as the emulation of another processor, may be executed in the system. A native mode instruction indicating a specified function for either one instruction or for a plurality of instructions, is first checked to determine proper format, after which a determination is made by means of the decor extension table, as to whether or not the system is capable of executing the specified function indicated by the native mode instruction.