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| − | '''Emacs''' is a class of [[text editor]]s, possessing an extensive set of features, that are popular with [[computer programmer]]s and other technically-proficient computer users. The original EMACS, a set of '''''E'''ditor '''MAC'''ro'''S''''' for the [[Text Editor and Corrector|TECO]] editor, was written in [[1976]] by [[Richard Stallman]], [[Guy L. Steele, Jr.|Guy Steele]], and [[Dave Moon]]. It was based on TECMAC and TMACS, a pair of TECO-macro editors written by Guy Steele, Dave Moon, [[Richard Greenblatt]], [[Charles Frankston]], and others. Many versions of Emacs have appeared over the years, but nowadays there are two that are commonly used: [[GNU Emacs]], written by [[Richard Stallman]] beginning in [[1984]], and [[XEmacs]], which [[fork (software)|forked]] from GNU Emacs in [[1991]]. Both use a powerful extension language, [[Emacs Lisp]], which allows them to handle tasks ranging from [[computer programming|writing]] and [[compiler|compiling]] [[computer program]]s to [[web browser|browsing the web]].
| + | emacs, written by Richard M. Stallman, is a text editor on crack. It has many modules -- sort of like plug-ins -- that allow you to do all sorts of stuff while still editing (e.g., checking your email.) (It should be noted, however, that despite its muscularity it still is primarily a text editor, ''not'' a word processor.) It is difficult to learn to use for most, but those who do often grow enamored of its versatility. |
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| − | Some people make a distinction between the lower-case word ''emacs'', which is used to refer to Emacs-like editors (particularly GNU Emacs and XEmacs), and the capitalized word ''Emacs'', which is used to refer to GNU Emacs. The word ''emacs'' is often pluralized as ''emacsen''.
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| − | Emacs is typically on one side of the [[editor war]]s, the other being [[vi]].
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| − | == Emacs history ==
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| − | Emacs began life at the [[MIT AI Lab]] during the [[1970s]]. Prior to its introduction, the default editor on [[Incompatible Timesharing System|ITS]], the [[operating system]] on the AI Lab's [[PDP-6]] and [[PDP-10]] computers, was a [[line editor]] known as [[Text_Editor_and_Corrector|TECO]]. Unlike modern text editors, TECO treated typing, editing, and document display separately. Typing characters into TECO did not place those characters directly into a document; one had to write a series of instructions in the TECO command language telling it to enter the required characters, during which time the edited text was not displayed on the screen. This behavior is similar to the program [[ed]], which is still in use.
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| − | Carl Mikkelsen, one of the [[hacker]]s at the AI Lab, added a display-editing mode to [[Text_Editor_and_Corrector|TECO]], allowing the screen display to be updated each time the user entered a keystroke. This more intuitive behavior, which is used by most modern text editors, had been pioneered by the "E" editor written at the [[Stanford University|Stanford]] AI Lab. In [[1974]], [[Richard Stallman]], another hacker, added a [[macro]] feature to the TECO display-editing mode, allowing the user to define certain keystrokes for performing multiple TECO commands.
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| − | The users at the AI Lab soon accumulated a large collection of custom macros. In [[1976]], [[Guy Steele]] took on the project of unifying the diverse macro sets into a single set. This task was completed by Stallman, who also wrote facilities for extending and documenting the new macro set. The resulting system was called EMACS, which stood for "Editor MACroS". According to Stallman, he picked the name Emacs "because <nowiki><E></nowiki> was not in use as an abbreviation on ITS at the time." It has also been pointed out that "[[Emack & Bolio's]]" was the name of a popular [[ice cream]] store in [[Boston, Massachusetts|Boston]], within walking distance of MIT. The text-formatting program used on ITS was called BOLIO. Stallman, however, denies that the ice cream was at all a factor in the naming of the editor, as he generally did not go to that store and had not liked their ice cream the one time he did try it.
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| − | Although EMACS was built on TECO, its behavior was different enough to be considered a text editor in its own right. It quickly became the standard editing program on ITS. It was also [[port (computer software)|ported]] from ITS to the [[Tenex]] and [[TOPS-20]] operating systems by Stallman and Michael McMahon.
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| − | Several Emacs-like editors were written in the following years, including EINE ("EINE Is Not EMACS") and ZWEI ("ZWEI Was EINE Initially"), which were written by Michael McMahon and Daniel Weinreb. In [[1978]], [[Bernard Greenberg]] wrote [[Multics]] Emacs at [[Honeywell]]'s Cambridge Information Systems Lab. Multics Emacs was written in [[MacLisp]], a dialect of the [[Lisp programming language]]. User-supplied extensions were also written in Lisp. The choice of Lisp provided more extensibility than ever before, and has been followed by most subsequent emacsen.
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| − | One early Emacs-like editor to run on [[Unix]] was Gosling Emacs, written by [[James Gosling]] in [[1981]]. It was written in [[C programming language|C]] and used an inconsequential dialect of Lisp, known as [[Mocklisp]], as an extension language.
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| − | In [[1984]], Stallman began working on [[GNU Emacs]], the first program in the nascent [[GNU|GNU project]]. GNU Emacs was written in C and used [[Emacs Lisp]] as an extension language. The first widely-distributed version of GNU Emacs was 15.34, which appeared in [[1985]]. (Versions 2 through 12 never existed. Earlier versions of GNU Emacs had been numbered "1.x.x", but sometime after version 1.12 the decision was made to drop the "1", as it was thought the major number would never change. Version 13, the first public release, was made on March 20, 1985.)
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| − | Like Gosling Emacs, GNU Emacs ran on Unix; however, GNU Emacs had more features, in particular a full-featured Lisp as extension language. As a result, it soon replaced Gosling Emacs as the ''de facto'' Emacs editor on Unix.
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| − | Beginning in [[1991]], Lucid Emacs was developed by [[Jamie Zawinski]] and others at Lucid Inc., based on an early alpha version of GNU Emacs 19. The codebases soon diverged, and the separate development teams gave up trying to merge them back into a single program. This was one of the most famous early [[code fork|forks]] of a [[free software]] program. Lucid Emacs has since been renamed [[XEmacs]]; it and GNU Emacs remain the two most popular varieties in use today.
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| − | == Features ==
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| − | The remainder of this article discusses GNU Emacs and XEmacs, the only incarnations of Emacs that are widely used today. We will use the term "Emacs" to refer to both programs, as they have very similar features; XEmacs started as a fork of GNU Emacs, and subsequent versions have remained more or less compatible with GNU Emacs.
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| − | In spite of—or perhaps because of—its venerable background, Emacs is one of the most powerful and versatile text editors in existence. It should be noted that it is primarily a ''text'' editor, not a [[word processor]]; its huge feature set is geared toward helping the user to manipulate pieces of text, rather than manipulating the [[Typeface|font]] of the characters or printing documents (though Emacs can do these as well). Emacs brings a host of features to bear on the seemingly-simple task of text editing, ranging from commands to manipulate [[word]]s and [[paragraph]]s (deleting them, moving them, moving through them, and so forth), to [[syntax highlighting]] for making [[source code]] easier to read, to executing "keyboard macros" for performing arbitrary batches of editing commands defined by the user.
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| − | The rich variety of features found in Emacs is a result of its unusual design. Almost all of the functionality in the editor, ranging from basic editing operations such as the insertion of characters into a document to the configuration of the user interface, is controlled by a dialect of the [[Lisp programming language]] known as [[Emacs Lisp]]. In this Lisp environment, [[variables]] and even entire [[function (programming)|functions]] can be modified on the fly, without having to recompile or even restart the editor. As a result, the behavior of Emacs can be modified almost without limit, either directly by the user, or (more commonly) by loading bodies of Emacs Lisp code known variously as "libraries", "packages", or "extensions".
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| − | Emacs contains a large number of Emacs Lisp libraries, and more "third-party" libraries can be found on the [[Internet]]. Many libraries implement computer programming aids, reflecting Emacs' popularity among programmers. Emacs can be used as an [[Integrated Development Environment]] (IDE), allowing programmers to edit, [[Compiler|compile]], and [[Debugging|debug]] their code within a single interface. Other libraries perform more unusual functions. A few examples are listed below:
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| − | * Calc, a powerful numerical [[calculator]]
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| − | * Calendar-mode, for keeping appointment calendars and diaries
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| − | * Doctor, an implementation of [[ELIZA]] that performs basic [[Carl Rogers|Rogerian]] [[psychotherapy]]
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| − | * [[Dunnet (game)|Dunnet]], a [[text adventure]]
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| − | * Emerge, for comparing files and combining them
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| − | * [[Emacs/W3]], a [[web browser]]
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| − | * [[ERC (software)|ERC]], an [[Internet Relay Chat|IRC]] client
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| − | * [[Gnus]], a full-featured [[newsreader]] and [[email client]]
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| − | * [[Tetris]]
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| − | The downside to Emacs' Lisp-based design is a performance overhead resulting from loading and [[interpreter (computing)|interpreting]] the Lisp code. On the systems in which Emacs was first implemented, Emacs was often noticeably slower than rival text editors. Several joke acronyms allude to this: ''Eight Megabytes And Constantly Swapping'' (from the days when eight [[megabyte]]s was a lot of memory), ''Emacs Makes A Computer Slow'', and ''Eventually [[Malloc]]s All Computer Storage''. However, modern computers are fast enough that Emacs is seldom felt to be slow. In fact, Emacs starts up more quickly than most modern word processors.
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| − | === Platforms ===
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| − | Emacs is one of the most [[porting|portable]] non-trivial computer programs in the world. It runs on a wide variety of [[operating system]]s, including most [[Unix]]-like systems ([[GNU/Linux]], the various [[Berkeley Software Distribution|BSDs]], [[Solaris Operating Environment|Solaris]], and [[AIX operating system|AIX]], etc.), [[MS-DOS]], [[Microsoft Windows]], [[OpenVMS]], and [[Mac OS X]].
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| − | Emacs runs on both [[TTY|text terminals]] and [[graphical user interface]] (GUI) environments. On [[Unix]]-like operating systems, Emacs uses the [[X Window System]] to produce its GUI, either directly or using a "widget toolkit" such as [[Motif (widget toolkit)|Motif]], [[LessTif]], or [[GTK|GTK+]]. Emacs can also use the native graphical systems of Mac OS X (using the [[Carbon (computing)|Carbon]] interface) and [[Microsoft Windows]]. The graphical interface provides [[menubar]]s, [[toolbar]]s, [[scrollbar]]s, and [[context menu]]s.
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| − | === Customization ===
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| − | Most users of Emacs customize the editor to suit their needs. There are two primary ways to customize Emacs. The first is the ''customize'' extension, which allows the user to set common customization variables, such as the colour scheme, using a graphical interface. This is intended for Emacs beginners who do not want to work with Emacs Lisp code.
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| − | The second method for customizing Emacs is using Emacs Lisp. Usually, user-supplied Emacs Lisp code is stored in a file called <code>.emacs</code>, which is loaded when Emacs starts up. The <code>.emacs</code> file is often used to set variables and [[Binding (computer science)|key bindings]] different from the default setting, and to define new commands that the user finds convenient. Many advanced users have <code>.emacs</code> files hundreds of lines long, with idiosyncratic customizations that cause Emacs to diverge wildly from the default behavior.
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| − | If a body of Emacs Lisp code is generally useful, it is often packaged as a library and distributed to other users. Many such third-party libraries can be found on the Internet; for example, there is a library called [[Wikipedia:Wikipedia-mode.el|wikipedia-mode]] for editing [[Wikipedia:How to edit a page#The wiki markup|Wikipedia articles]]. There is even a [[Usenet]] [[newsgroup]], [news://gnu.emacs.sources gnu.emacs.sources], which is used for posting new libraries. Some third-party libraries eventually make their way into Emacs, thus becoming a "standard" library.
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| − | === Documentation ===
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| − | Emacs includes a powerful ''help'' library that can display the documentation for every single command, variable, and internal function. Because of this, Emacs is sometimes described as a "self-documenting" text editor. This description, which originated in the days when few programs contained built-in help systems, may be somewhat misleading. Emacs does ''not'' write its own documentation; what "self-documentation" means is that Emacs displays the documentation using its own interface, instead of launching a separate "help browser". This makes Emacs' documentation very accessible. For example, the user can find out about the command bound to a particular keystroke simply by entering <code>C-h k</code> (which runs the command <code>describe-key</code>), followed by the keystroke.
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| − | The Emacs ''help'' system is useful not only for beginners, but also for advanced users writing Emacs Lisp code. If the documentation for a function or variable is not enough, the ''help'' system can be used to browse the Emacs Lisp source code for both built-in libraries and installed third-party libraries. It is therefore very convenient to program in Emacs Lisp using Emacs itself.
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| − | Apart from the built-in documentation, Emacs has an unusually long, detailed and well-written [[manual]]. An electronic copy of the ''GNU Emacs Manual'', written by Richard Stallman, is included with GNU Emacs and can be viewed with the built-in [[Texinfo|Info]] browser. XEmacs has a similar manual, which forked from the GNU Emacs Manual at the same time as the XEmacs software. Two other manuals, the ''Emacs Lisp Reference Manual'' by Bill Lewis, Richard Stallman, and Dan Laliberte, and ''Programming in Emacs Lisp'' by Robert Chassell, are also included. Apart from the electronic versions, all three manuals are also available in book form, published by the [[Free Software Foundation]].
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| − | Emacs also has a built-in [[tutorial]]. When Emacs is started with no file to edit, it displays instructions for performing simple editing commands and invoking the tutorial.
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| − | === Internationalization ===
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| − | Emacs supports the editing of text written in many [[Language|human languages]]. There is support for many alphabets, scripts, writing systems, and cultural conventions. Emacs provides spell checking for many languages by calling external programs such as [[ispell]]. Many [[Character encoding|encoding systems]], including [[UTF-8]], are supported. XEmacs version 21.5 has full [[Unicode]] support, and similar support for GNU Emacs is being developed. However, the Emacs user interface is in English, and has not been translated into any other language.
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| − | For visually impaired and blind users, there is a subsystem called ''Emacspeak'' which allows the editor to be used through audio feedback only.
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| | == Using Emacs == | | == Using Emacs == |
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| | Some Emacs commands work by invoking an external program (such as [[ispell]] for spell-checking or [[GNU Compiler Collection|gcc]] for program compilation), parsing the program's output, and displaying the result in Emacs. | | Some Emacs commands work by invoking an external program (such as [[ispell]] for spell-checking or [[GNU Compiler Collection|gcc]] for program compilation), parsing the program's output, and displaying the result in Emacs. |
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| − | === File management and display ===
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| − | Emacs keeps text in objects called ''buffers''. The user can create new buffers and dismiss unwanted ones, and several buffers can exist at the same time. Most buffers contain text loaded from [[Binary and text files|text files]], which the user can edit and save back to disk. Buffers are also used to store temporary text, such as the documentation strings displayed by the ''help'' library.
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| − | In both text terminal and graphical modes, Emacs is able to split the editing area into separate sections, so that more than one buffer can be displayed at a time. This has many uses. For example, one section can be used to display the [[source code]] of a program, while another displays the results from compiling the program. In graphical environments, Emacs can also launch multiple [[window (computing)|windows]] (which it calls "frames") for a similar purpose.
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| − | === Editing modes ===
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| − | Emacs adapts its behavior to the type of text it is editing by entering editing modes called "major modes". Major modes are defined for ordinary text files, [[source code]] for many [[programming language]]s, [[HTML]] documents, [[TeX]] and [[LaTeX]] documents, and many other types of text. Each major mode tweaks certain Emacs Lisp variables to make Emacs behave more conveniently for the particular type of text. In particular, they usually implement [[syntax highlighting]], using different fonts or colors to display [[keyword]]s, [[comment]]s, and so forth. Major modes also provide special editing commands; for example, major modes for programming languages usually define commands to jump to the beginning and the end of a function.
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| − | The behavior of Emacs can be further customized using "minor modes". While only one major mode can be associated with a buffer at a time, multiple minor modes can be simultaneously active. For example, the major mode for the C programming language defines a different minor mode for each of the popular [[indent style]]s.
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| − | == License ==
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| − | The source code, including both the C and Emacs Lisp components, is freely available for examination, modification, and redistribution, under the terms of the [[GNU General Public License]] (GPL). Older versions of the GNU Emacs documentation were released under a modified GPL which forced the inclusion of certain text in any modified copy. In the GNU Emacs user's manual, for example, this included how to obtain GNU Emacs and Richard Stallman's political essay '''The GNU Manifesto'''. The XEmacs manuals, which were inherited from older GNU Emacs manuals when the fork occurred, have the same license. The newer versions of the GNU Emacs documentation, meanwhile, uses the [[GNU Free Documentation License]] and makes use of "invariant sections" to force the inclusion of the same documents, additionally requiring that the manuals proclaim themselves as ''GNU Manuals'', whether or not this would be accurate.
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| − | ==See also==
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| − | *[[List of text editors]]
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| − | *[[Comparison of text editors]]
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| − | *[[Wikipedia:Text editor support#Emacs|Editing Wikipedia articles with Emacs]]
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| − | *[[Emacs-wiki]]
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| | ==References== | | ==References== |
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| | ==External links== | | ==External links== |
| | + | *[http://en.wikipedia.org/wiki/Emacs Wikipedia.org's Emacs article] |
| | *[http://www.gnu.org/software/emacs/emacs.html The GNU Emacs homepage] | | *[http://www.gnu.org/software/emacs/emacs.html The GNU Emacs homepage] |
| | *[http://www.xemacs.org/ The XEmacs homepage] | | *[http://www.xemacs.org/ The XEmacs homepage] |
emacs, written by Richard M. Stallman, is a text editor on crack. It has many modules -- sort of like plug-ins -- that allow you to do all sorts of stuff while still editing (e.g., checking your email.) (It should be noted, however, that despite its muscularity it still is primarily a text editor, not a word processor.) It is difficult to learn to use for most, but those who do often grow enamored of its versatility.
In the normal editing mode, Emacs behaves just like other text editors: the character keys (a, b, c, 1, 2, 3, etc.) insert the corresponding characters, the arrow keys move the editing point, backspace deletes text, and so forth. Other commands are invoked with modified keystrokes, using the control key and/or the meta key/alt key. Every editing command is actually a call to a function in the Emacs Lisp environment. Even a command as simple as typing a to insert the character a involves calling a function -- in this case, self-insert-command.
Some of the basic commands are shown below. The control key is denoted by a capital C, and the meta or alt key by a capital M.
When Emacs is running a graphical interface, many commands can be invoked from the menubar or toolbar instead of using the keyboard. However, many experienced Emacs users prefer to use the keyboard anyway, because it is faster and more convenient once the necessary keystrokes have been memorized.
