| 摘要 |
The system has a flexible internal structure, protected from and effectively invisible to users, with multilevel control and stack mechanisms and the capability of performing multiple, concurrent operations, and providing a flexible, simplified interface to users. The system comprises a plurality of separate, independent job processors (10114) and a memory (10112). Each processor includes a fetch unit (10120) and an execute unit (10122) and the fetch unit structures operands and instructions into objects. The fetch unit includes a register address generator generating unique and permanent identifier codes for the objects. The memory (10112) includes sections storing procedure objects, including a name table providing the operand addresses in the memory. The memory (10112) also includes protection tables for preventing a user obtaining access to objects private to others. The protection tables operate in association with a protection cache in the fetch unit (10120) and an active subject number register which stores a currently active number identifying the user, the procedure he is using and the type of operation instructed. The protection tables store an access control list establishing the access rights of the subjects and the protection cache in the fetch unit (10120) controls access to the objects by comparing the currently active subject number with the requested object. The fetch unit includes a descriptor processor performing the operations required by the instructions and first and second microcode control means storing first and second sequences of microinstructions for controlling the descriptor processor, the first sequences being S-language instructions which have a uniform, fixed format in an intermediate level language. |
