A communication system is presented which consists of a switch (Datakit [Fraser 1979]) with associated control and interface hardware and software. The switch offers virtual circuit service which is internally implemented through packet switching. The users of the communication system are operating systems; using our communication system, we have implemented a network of UNIXTM systems and a new distributed operating system derived from UNIX. Our work concentrated on the performance of the subscriber-switch interface; on the reliability and recoverability of the switching service; and on the exploitation of the circuit concept for operating system design.

The popular UNIXTM operating system provides time-sharing service on a single computer. This paper reports on the design and implementation of a distributed UNIX system. The new operating system consists of two components: the S-UNIX subsystem provides a complete UNIX process environment enhanced by access to remote files; the F-UNIX subsystem is specialized to offer remote file service. A system can be configured out of many computers which operate either under the S-UNIX or the F-UNIX operating subsystem. The file servers together present the view of a single global file system. A single-service view is presented to any user terminal connected to one of the S-UNIX subsystems.

This book evolved from notes for a seminar with the same title which has been given repeatedly at the Institute for Advanced Technology, a directorate of CDC. It intends to present an integrated guideline for the design of on-line computer systems, focusing on technical (rather than managerial) aspects, although it may help the manager to maintain a fundamental understanding of what his programmers and analysts are up to. Its six parts are meant to be basically independent, and the following is an overview of their contents.

A short-turnaround graphical hard-copy system called Stare 2 has been designed and is in use at Bell Telephone Laboratories. It produces prints using a 1024x1436 matrix of overlapping dots on 11-by 17-in paper, at a speed of 2 to 10 prints per min. The system is connected to a large central computer (IBM System/370 Model 165), thus making pictures available within seconds of a program run. The output mechanism is a Gould Clevite 4800 electrographic printer with the stylus assembly modified to permit overlapping dots. A DEC PDP-15 computer controls the printer and also converts the data to the format required to drive the printer. Output may be produced at a location remote from the central computer since the connection to the hard-copy system is via a 2000-Bd transmission system.