Butler W. Lampson
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A terminal-oriented communication system
This paper describes a system for full-duplex communication between a time-shared computer and its terminals. The system consists of a communications computer directly connected to the time-shared system, a number of small remote computers to which the terminals are attached, and connecting medium speed telephone lines. It can service a large number of terminals of various types. The overall system design is presented along with the algorithms used to solve three specific problems: local echoing, error detection and correction on the telephone lines, and multiplexing of character output.
Reflections on an operating system design
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.
A note on the confinement problem
onfining a program during its execution so that it cannot transmit information to any other program except its caller. A set of examples attempts to stake out the boundaries of the problem. Necessary conditions for a solution are stated and informally justified.
An online, interactive system for text editing is described in detail, with remarks on the theoretical and experimental justification for its form. Emphasis throughout the system is on providing maximum convenience and power for the user. Notable features are its ability to handle any piece of text, the content-searching facility, and the character-by-character editing operations. The editor can be programmed to a limited extent.
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