© 1976 by British Computer Society
Toward the understandability of an operating system*
Bell Laboratories 1C-406A Holmdel, New Jersey, USA
Design considerations are presented for the construction of an operating system. (This approach emphasises the need to understand the interrelationships among all operating system components to facilitate the inevitable growth and development of a useful system). The concept of a process and a resource are defined in such a way that a resource-to-process concept is developed, which is later used to provide an ‘individualised’ virtual environment for a process. Terminology is introduced to distinguish between so-called S and type M resources, which must be treated differently for resource sharing. The levels of abstraction are described for the tree structured operating system that evolved from the design considerations. Within the tree, resource sharing is allowed and controlled by a communication language and so-called resource tables. Since the system was designed for use on a PDP-11/45, the basic components of its tree are given. It is then suggested that the tree presented here is, in fact, a basic framework upon which different specific operating systems may be built.
Received March 1974.
* Portions of the work done at The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
Bell Laboratories 1C-406A Holmdel, N. J. 07733, USA