2740	 A Large Semaphore Based Operating System	 The paper describes the internal structure of a large operating system as a set of cooperating sequential processes. The processes synchronize by means of semaphores and extended semaphores queue semaphores . The number of parallel processes is carefully justified and the various semaphore constructions are explained. The system is proved to be free of deadly embrace deadlock . The design principle is an alternative to Dijkstra s hierarchical structuring of operating systems. The project management and the performance are discussed too. The operating system is the first large one using the RC multiprogramming system. cooperating processes operating system semaphores semaphore applications queue semaphores deadlock deadly embrace hierarchical structuring multiprogramming operating system structure asynchronous structuring buffering parallel processes synchronizing primitives reentrant code RC project management time schedule debugging project planning project scheduling reliability program proving coroutines correctness program maintenance software paging
