Importance

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Abstract

An integrated data processing and communication service is provided by a system which comprises a plurality of nodes interconnected via a packet-switched transport network. Each node includes a database processor and at least one node processor, with a number of terminals and hosts being connected to the latter via at least one front-end processor. Processes existing with each node processor are two types--application layer processes which perform 'useful work' on behalf of the customers and the vendor of the service, and control layer processes, each of which manages, or provides some part of, the service itself. The processors are virtual memory processors and the program region of the virtual address space of each process includes both a process-specific image and shared image. The former is weakly linked to the latter and provides it, via a set of primitives, with a number of communications processing services including file/database management, application program control, interprocess communications, station access and message services. Such services are also available for use within the shared image itself. The shared image also provides a number of 'supervisor' services including enforcement of a system of privileges for the primitives; memory allocation; condition handling; event services; and establishment and management of the tasking system.

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First Claim