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 4000 
multiprogramming system.
CACM July, 1975
Lauesen, S.
