Emacs Statusline

Emacs , originally named EMACS (an acronym for "Editor MACroS"), is a family of text editors that are characterized by their extensibility. The manual for the most widely used variant, GNU Emacs, describes it as "the extensible, customizable, self-documenting, real-time display editor". Development of the first Emacs began in the mid-1970s, and work on its direct descendant, GNU Emacs, continues actively; the latest version is 28.2, released in September 2022.

Emacs has over 10,000 built-in commands and its user interface allows the user to combine these commands into macros to automate work. Implementations of Emacs typically feature a dialect of the Lisp programming language, allowing users and developers to write new commands and applications for the editor. Extensions have been written to, among other things, manage files, remote access, e-mail, outlines, multimedia, git integration, and RSS feeds, as well as implementations of ''ELIZA'', ''Pong'', '' Conway's Life'', ''Snake'', ''Dunnet'', and ''Tetris''.

The original EMACS was written in 1976 by David A. Moon and Guy L. Steele Jr. as a set of Editor MACroS for the TECO editor. It was inspired by the ideas of the TECO-macro editors TECMAC and TMACS.

The most popular, and most ported, version of Emacs is GNU Emacs, which was created by Richard Stallman for the GNU Project. XEmacs is a variant that branched from GNU Emacs in 1991. GNU Emacs and XEmacs use similar Lisp dialects and are, for the most part, compatible with each other. XEmacs development is inactive.

Emacs is, along with vi, one of the two main contenders in the traditional editor wars of Unix culture. Emacs is among the oldest free and open source projects still under development.

History

Emacs development began during the 1970s at the MIT AI Lab, whose PDP-6 and PDP-10 computers used the Incompatible Timesharing System (ITS) operating system that featured a default line editor known as Tape Editor and Corrector (TECO). Unlike most modern text editors, TECO used separate modes in which the user would either add text, edit existing text, or display the document. One could not place characters directly into a document by typing them into TECO, but would instead enter a character ('i') in the TECO command language telling it to switch to input mode, enter the required characters, during which time the edited text was not displayed on the screen, and finally enter a character () to switch the editor back to command mode. (A similar technique was used to allow overtyping.) This behavior is similar to that of the program ed.

Richard Stallman visited the Stanford AI Lab in 1976 and saw the lab's ''E'' editor, written by Fred Wright. He was impressed by the editor's intuitive WYSIWYG (What You See Is What You Get) behavior, which has since become the default behavior of most modern text editors. He returned to MIT where Carl Mikkelsen, a hacker at the AI Lab, had added to TECO a combined display/editing mode called ''Control-R'' that allowed the screen display to be updated each time the user entered a keystroke. Stallman reimplemented this mode to run efficiently and then added a macro feature to the TECO display-editing mode that allowed the user to redefine any keystroke to run a TECO program.

E had another feature that TECO lacked: random-access editing. TECO was a page-sequential editor that was designed for editing paper tape on the PDP-1 at a time when computer memory was generally small due to cost, and it was a feature of TECO that allowed editing on only one page at a time sequentially in the order of the pages in the file. Instead of adopting E's approach of structuring the file for page-random access on disk, Stallman modified TECO to handle large buffers more efficiently and changed its file-management method to read, edit, and write the entire file as a single buffer. Almost all modern editors use this approach.

The new version of TECO quickly became popular at the AI Lab and soon accumulated a large collection of custom macros whose names often ended in ''MAC'' or ''MACS'', which stood for ''macro''. Two years later, Guy Steele took on the project of unifying the diverse macros into a single set. Steele and Stallman's finished implementation included facilities for extending and documenting the new macro set. The resulting system was called EMACS, which stood for ''Editing MACroS'' or, alternatively, ''E with MACroS''. Stallman picked the name Emacs "because was not in use as an abbreviation on ITS at the time." An apocryphal hacker koan alleges that the program was named after '' Emack & Bolio's'', a popular Boston ice cream store. The first operational EMACS system existed in late 1976.

Stallman saw a problem in too much customization and ''de facto'' forking and set certain conditions for usage. He later wrote:

The original Emacs, like TECO, ran only on the PDP-10 running ITS. Its behavior was sufficiently different from that of TECO that it could be considered a text editor in its own right, and it quickly became the standard editing program on ITS. Mike McMahon ported Emacs from ITS to the TENEX and TOPS-20 operating systems. Other contributors to early versions of Emacs include Kent Pitman, Earl Killian, and Eugene Ciccarelli. By 1979, Emacs was the main editor used in MIT's AI lab and its Laboratory for Computer Science.

Implementations

Early implementations

In the following years, programmers wrote a variety of Emacs-like editors for other computer systems. These included EINE (''EINE Is Not EMACS'') and ZWEI (''ZWEI Was EINE Initially''), which were written for the Lisp machine by Mike McMahon and Daniel Weinreb, and Sine (''Sine Is Not Eine''), which was written by Owen Theodore Anderson. Weinreb's EINE was the first Emacs written in Lisp. In 1978, Bernard Greenberg wrote Multics Emacs almost entirely in Multics Lisp at Honeywell's Cambridge Information Systems Lab. Multics Emacs was later maintained by Richard Soley, who went on to develop the NILE Emacs-like editor for the NIL Project, and by Barry Margolin. Many versions of Emacs, including GNU Emacs, would later adopt Lisp as an extension language.

James Gosling, who would later invent NeWS and the Java programming language, wrote Gosling Emacs in 1981. The first Emacs-like editor to run on Unix, Gosling Emacs was written in C and used Mocklisp, a language with Lisp-like syntax, as an extension language.

Early Ads for Computer Corporation of America's ''CCA EMACS'' (Steve Zimmerman). appeared in 1984. 1985 comparisons to GNU Emacs, when it came out, mentioned free vs. $2,400.

GNU Emacs

Richard Stallman began work on GNU Emacs in 1984 to produce a free software alternative to the proprietary Gosling Emacs. GNU Emacs was initially based on Gosling Emacs, but Stallman's replacement of its Mocklisp interpreter with a true Lisp interpreter required that nearly all of its code be rewritten. This became the first program released by the nascent GNU Project. GNU Emacs is written in C and provides Emacs Lisp, also implemented in C, as an extension language. Version 13, the first public release, was made on March 20, 1985. The first widely distributed version of GNU Emacs was version 15.34, released later in 1985. Early versions of GNU Emacs were numbered as ''1.x.x'', with the initial digit denoting the version of the C core. The ''1'' was dropped after version 1.12, as it was thought that the major number would never change, and thus the numbering skipped from ''1'' to ''13''. In September 2014, it was announced on the GNU emacs-devel mailing list that GNU Emacs would adopt a rapid release strategy and version numbers would increment more quickly in the future.

GNU Emacs offered more features than Gosling Emacs, in particular a full-featured Lisp as its extension language, and soon replaced Gosling Emacs as the ''de facto'' Unix Emacs editor. Markus Hess exploited a security flaw in GNU Emacs' email subsystem in his 1986 cracking spree in which he gained superuser access to Unix computers.

Most of GNU Emacs functionality is implemented through a scripting language called Emacs Lisp. Because about 70% of GNU Emacs is written in the Emacs Lisp extension language, one only needs to port the C core which implements the Emacs Lisp interpreter. This makes porting Emacs to a new platform considerably less difficult than porting an equivalent project consisting of native code only.

GNU Emacs development was relatively closed until 1999 and was used as an example of the ''Cathedral'' development style in ''The Cathedral and the Bazaar''. The project has since adopted a public development mailing list and anonymous CVS access. Development took place in a single CVS trunk until 2008 and was then switched to the Bazaar DVCS. On November 11, 2014, development was moved to Git.

Richard Stallman has remained the principal maintainer of GNU Emacs, but he has stepped back from the role at times. Stefan Monnier and Chong Yidong were maintainers from 2008 to 2015. John Wiegley was named maintainer in 2015 after a meeting with Stallman at MIT. As of early 2014, GNU Emacs has had 579 individual committers throughout its history.

XEmacs

Lucid Emacs, based on an early alpha version of GNU Emacs 19, was developed beginning in 1991 by Jamie Zawinski and others at Lucid Inc. One of the best-known early forks in free software development occurred when the codebases of the two Emacs versions diverged and the separate development teams ceased efforts to merge them back into a single program. Lucid Emacs has since been renamed XEmacs. Its development is currently inactive, with the most recent stable version 21.4.22 released in January 2009 (while a beta was released in 2013), while GNU Emacs has implemented many formerly XEmacs-only features.

Other forks of GNU Emacs

Other notable forks include:

* Aquamacs – based on GNU Emacs (Aquamacs 3.2 is based on GNU Emacs version 24 and Aquamacs 3.3 is based on GNU Emacs version 25) which focuses on integrating with the Apple Macintosh user interface
*Meadow – a Japanese version for Microsoft Windows
* SXEmacs – Steve Youngs' fork of XEmacs

Various Emacs editors

In the past, projects aimed at producing small versions of Emacs proliferated. GNU Emacs was initially targeted at computers with a 32-bit flat address space and at least 1 MiB of RAM. Such computers were high end workstations and minicomputers in the 1980s, and this left a need for smaller reimplementations that would run on common personal computer hardware. Today's computers have more than enough power and capacity to eliminate these restrictions, but small clones have more recently been designed to fit on software installation disks or for use on less capable hardware.

Other projects aim to implement Emacs in a different dialect of Lisp or a different programming language altogether. Although not all are still actively maintained, these clones include:

* MicroEMACS, which was originally written by Dave Conroy and further developed by Daniel Lawrence and which exists in many variations.
* mg, originally called MicroGNUEmacs and, later, mg2a, a public-domain offshoot of MicroEMACS intended to more closely resemble GNU Emacs. Now installed by default on OpenBSD.
*JOVE (Jonathan's Own Version of Emacs), Jonathan Payne's non-programmable Emacs implementation for UNIX-like systems.
* MINCE (MINCE Is Not Complete Emacs), a version for CP/M and later DOS, from Mark of the Unicorn. MINCE evolved into Final Word, which eventually became the Borland Sprint word processor.
* Perfect Writer, a CP/M implementation derived from MINCE that was included circa 1982 as the default word processor with the very earliest releases of the Kaypro II and Kaypro IV. It was later provided with the Kaypro 10 as an alternative to WordStar.
* Freemacs, a DOS version that uses an extension language based on text macro expansion and fits within the original 64 KiB flat memory limit.
* Zile. Zile was a recursive acronym for ''Zile Is Lossy Emacs'', but the project was rewritten in Lua and now gives the expansion as Zile Implements Lua Editors. The new Zile still includes an implementation of Emacs in Lua called Zemacs. There is also an implementation of vi called Zi.
* Zmacs, for the MIT Lisp Machine and its descendants, implemented in ZetaLisp.
* Climacs, a Zmacs-influenced variant implemented in Common Lisp.
*Epsilon, an Emacs clone by Lugaru Software. Versions for DOS, Windows, Linux, FreeBSD, Mac OS X and O/S 2 are bundled in the release. It uses a non-Lisp extension language with C syntax and used a very early concurrent command shell buffer implementation under the single-tasking MS-DOS.
* PceEmacs is the Emacs-based editor for SWI-Prolog.
* Amacs, an Apple II ProDOS version of Emacs implemented in 6502 assembly by Brian Fox.
* Hemlock, originally written in Spice Lisp, then Common Lisp. A part of CMU Common Lisp. Influenced by Zmacs. Later forked by Lucid Common Lisp (as Helix), LispWorks

HOME


Content is Copyleft
Website design, code, and AI is Copyrighted (c) 2014-2017 by Stephen Payne


Consider donating to Wikimedia



As an Amazon Associate I earn from qualifying purchases