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This paper describes the philosophy and structure of a multi-programming system that can be extended with a hierarchy of operating systems to suit diverse requirements of program scheduling and resource allocation. The system nucleus simulates an environment in which program execution and input/output are handled uniformly as parallel, cooperating processes. A fundamental set of primitives allows the dynamic creation and control of a hierarchy of processes as well as the communication among them.
Per Brinch Hansen (Wed,) studied this question.