Multics Emacs History/Design/Implementation (1979)

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[系统(linux) 所属分类 系统(linux) | 发布者 店小二03 | 时间 2016 | 作者 红领巾 ] 0人收藏点击收藏
Multics Emacs: The History, Design and Implementation

Copyright 1979, 1996 Bernard S. Greenberg

April 8, 1996

What follows is my vast, unpublished 1979 "Mother of All Multics Emacs papers" from which all of my lesser and greater Emacs papers, published, internal, and unpublished, were ultimately excerpted, including Prose and CONS: A Commercial Text-Processing System in Lisp in the 1980 Lisp Conference proceedings and the 1980 Honeywell conference paper. It's about time to expose it, and the WWW/HTML is now the ideal vehicle.

Multics is no longer produced or offered for sale;Honeywell no longer even makes computers. People edit on computers on their desktop so cheap and fast that not only do redisplay algorithms no longer matter, but the whole idea of autonomous redisplay in a display editor is no longer a given (although autonomous redisplay's illustrious child, WYSIWYG, is now the standard paradigm of the industry.). There is now no other kind of editor besides what we then called the "video editor". Thus, all of the battles, acrimony, and invidious or arrogant comparisons in what follows are finished and done with, and to be viewed in the context of 1979 -- this is a historical document about Multics and the evolution of an editor. It is part of the histories of Multics, of Emacs, and of Lisp.

Many of the deficiencies of Multics described here were thereafter remedied, not only by Emacs, but by a managed-video system inspired by Emacs. Although it started out as rebellious "hack", Multics Emacs became an integral part of the Multics product.

The termARPANET refers to the early stages of what is now called the INTERNET . ARPA was the Advanced Research Projects Agency of the U.S. Department of Defense, who instigated and underwrote its development.

Please enjoy.

David Mery posted an interesting story about Multics Emacs on 14 Nov 2007: "Multics source reveals le jetteur des gazongues" .

The source for Multics Emacs is available online at MIT


Table of Contents I. Prehistory of Editing on Multics II. History of Video-oriented Editing on ITS III. Inception of Multics Emacs IV. Multics Emacs: The Embryonic Phase and Basic Decisions V. Early Enhancements VII. The SUPDUP-OUTPUT ARPANET Protocol VIII. The Place of Emacs in Multics IX. Experience and Conclusions Appendix A. The Redisplay Appendix B. The Extension Language

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Multics Emacs: The History, Design and Implementation Bernard S. Greenberg -- 15 August 1979 (Paper on Multics Emacs, intended audience unclear. Idea is to put this stuff down on "paper" for posterity.) Brackets ([xxx]) denote references to the Bibliography at the end of the main text. Multics Emacs is a video-oriented text preparation and editing system running on Honeywell's Multics [Multics] system, being distributed as an experimental offering in Multics Release 7.0. From the viewpoint of Multics, it represents the first video-management software to be implemented, the first time character-at-a-time-interaction has been used, and a radical and complete departure from other editing and text preparation tools and techniques prevalent on Multics. From the viewpoint of similar systems running elsewhere, several features are noteworthy, including a major commitment to the programming language Lisp [Moonual] [Chineual], user-accessible extensibility through Lisp, and an internal implementation designed from the start (as is often not the case) with display-oriented editing in mind. The seemingly innate expense of video-oriented interaction has also led to the development of performance enhancement techniques applicable to any such system. The growth of Multics Emacs and its user community on MIT's Multics system has also led to the development of protocols on for the ARPANET [Arpanet] designed to facilitate the use of video-oriented software in a device-independent fashion.

Multics Emacs is currently in widespread use at three Multics exposure/development sites, serving about 60 regular users. Due to the lack of previous video-oriented software on Multics, not many users have a large number of high-speed video terminals connected to their Multics system. Thus, much usage of Multics Emacs is via 300- and 1200-baud dialup lines. This fact, combined with the acknowledged expense and resource consumption of Multics Emacs, places Multics Emacs among a choice of editing tools: given current resource economies and communications devices at current sites, it is not always the tool of choice, even among its most fervid partisans.

This paper describes the background and history of Multics Emacs, the previous developments, and the climate in which it was created. As many of the salient features and design and implementation criteria and decisions as possible are stated, as well as experience with the design and implementation. Where important, complete algorithms are detailed, notably the redisplay algorithm , detailed in the.

I. Prehistory of Editing on Multics Four editors were in common use on Multics before the introduction of Multics Emacs. They are still in widespread use. Two of them, "edm" [MPM] and "qedx" [QUG], are standard, and intended as end-user interfaces. Both of these editors are line-oriented, printing-terminal editors of a conventional mold. When in command mode , lines full of editor commands are typed to effect the positioning to, printing, deleting, or changing (by string substitution) of lines, or entry into input mode , which is the only way new text may be entered. The typing of a reserved character sequence exits input mode back to command mode. These editors maintain buffers (edm maintains one text buffer, qedx many) as character strings with a gap in the middle, which represents the current point at which text may be inserted. Neither editor can address individual characters. The edm editor is extremely limited, is not programmable, and intended for novice users. It was developed from the EDL [CTSS] editor interface on CTSS. The qedx editor was developed as a stripped-down (for runtime efficiency) version of the QED editor [CTSS] [Bell QED], also on CTSS. (Many of the original Multics developers had worked on CTSS). Both editors are oriented towards a low-speed, half-duplex, printing terminal interface, where minimal typeout is a design criterion. It was solely with these editors that the bulk of the Multics operating system and applications were entered, edited, and maintained. An implementation of TECO (a version of which is the standard DEC editor) was built on Multics in 1971. This version was derived from the original TECO implementation, on the MIT AI Lab's PDP-10 [TECDOC]. Unlike the latter, Multics TECO has no display support, and does not have the complex control-structure constructs of the AI Lab editor. Multics TECO is supported by Honeywell as a tool, which is to say, not

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