Butler W. Lampson and Howard E. Sturgis

Citation: B. Lampson and H. Sturgis. Reflections on an operating system design. Comm. ACM 19, 5 (May 1976), pp 251-265.

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Email: blampson@microsoft.com. This paper is at http://www.research.microsoft.com.

The main features of a general purpose multiaccess operating system developed for the CDC 6400 at Berkeley are presented, and its good and bad points are discussed as they appear in retrospect. Distinctive features of the design were the use of capabilities for protection, and the organization of the system into a sequence of layers, each building on the facilities provided by earlier ones and protecting itself from the malfunctions of later ones. There were serious problems in maintaining the protection between layers when levels were added to the memory hierarchy; these problems are discussed and a new solution is described.