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## Glossary

Abbrev

An abbrev is a text string that expands into a different text string when present in the buffer. For example, you might define a few letters as an abbrev for a long phrase that you want to insert frequently. See Abbrevs.

Aborting

Aborting means getting out of a recursive edit (q.v.). The commands C-] and M-x top-level are used for this. See Quitting.

Active Region

Setting the mark (q.v.) at a position in the text also activates it. When the mark is active, we call the region an active region. See Mark.

Alt

Alt is the name of a modifier bit that a keyboard input character may have. To make a character Alt, type it while holding down the Alt key. Such characters are given names that start with Alt- (usually written A- for short). (Note that many terminals have a key labeled Alt that is really a META key.) See Alt.

Argument
ASCII character

An ASCII character is either an ASCII control character or an ASCII printing character. See User Input.

ASCII control character

An ASCII control character is the Control version of an upper-case letter, or the Control version of one of the characters ‘@[\]^_?’.

ASCII printing character

ASCII letters, digits, space, and the following punctuation characters: ‘!@#%^&*()_-+=|\~{}[]:;"'<>,.?/’. Auto Fill Mode Auto Fill mode is a minor mode (q.v.) in which text that you insert is automatically broken into lines of a given maximum width. See Filling. Auto Saving Auto saving is the practice of periodically saving the contents of an Emacs buffer in a specially-named file, so that the information will be preserved if the buffer is lost due to a system error or user error. See Auto Save. Autoloading Emacs can automatically load Lisp libraries when a Lisp program requests a function from those libraries. This is called “autoloading”. See Lisp Libraries. Backtrace A backtrace is a trace of a series of function calls showing how a program arrived at a certain point. It is used mainly for finding and correcting bugs (q.v.). Emacs can display a backtrace when it signals an error or when you type C-g (see Glossary---Quitting). See Checklist. Backup File A backup file records the contents that a file had before the current editing session. Emacs makes backup files automatically to help you track down or cancel changes you later regret making. See Backup. Balancing Parentheses Emacs can balance parentheses (or other matching delimiters) either manually or automatically. You do manual balancing with the commands to move over parenthetical groupings (see Moving by Parens). Automatic balancing works by blinking or highlighting the delimiter that matches the one you just inserted, or inserting the matching delimiter for you (see Matching Parens). Balanced Expressions A balanced expression is a syntactically recognizable expression, such as a symbol, number, string constant, block, or parenthesized expression in C. See Balanced Expressions. Balloon Help Base Buffer A base buffer is a buffer whose text is shared by an indirect buffer (q.v.). Bidirectional Text Some human languages, such as English, are written from left to right. Others, such as Arabic, are written from right to left. Emacs supports both of these forms, as well as any mixture of them—this is “bidirectional text”. See Bidirectional Editing. Bind To bind a key sequence means to give it a binding (q.v.). See Rebinding. Binding A key sequence gets its meaning in Emacs by having a binding, which is a command (q.v.), a Lisp function that is run when you type that sequence. See Binding. Customization often involves rebinding a character to a different command function. The bindings of all key sequences are recorded in the keymaps (q.v.). See Keymaps. Blank Lines Blank lines are lines that contain only whitespace. Emacs has several commands for operating on the blank lines in the buffer. See Blank Lines. Bookmark Bookmarks are akin to registers (q.v.) in that they record positions in buffers to which you can return later. Unlike registers, bookmarks persist between Emacs sessions. See Bookmarks. Border A border is a thin space along the edge of the frame, used just for spacing, not for displaying anything. An Emacs frame has an ordinary external border, outside of everything including the menu bar, plus an internal border that surrounds the text windows, their scroll bars and fringes, and separates them from the menu bar and tool bar. You can customize both borders with options and resources (see Borders X). Borders are not the same as fringes (q.v.). Buffer The buffer is the basic editing unit; one buffer corresponds to one text being edited. You normally have several buffers, but at any time you are editing only one, the current buffer, though several can be visible when you are using multiple windows or frames (q.v.). Most buffers are visiting (q.v.) some file. See Buffers. Buffer Selection History Emacs keeps a buffer selection history that records how recently each Emacs buffer has been selected. This is used for choosing a buffer to select. See Buffers. Bug A bug is an incorrect or unreasonable behavior of a program, or inaccurate or confusing documentation. Emacs developers treat bug reports, both in Emacs code and its documentation, very seriously and ask you to report any bugs you find. See Bugs. Button Down Event A button down event is the kind of input event (q.v.) generated right away when you press down on a mouse button. See Mouse Buttons. By Default Byte Compilation C- C- in the name of a character is an abbreviation for Control. See C-. C-M- C-M- in the name of a character is an abbreviation for Control-Meta. If your terminal lacks a real META key, you type a Control-Meta character by typing ESC and then typing the corresponding Control character. See C-M-. Case Conversion Case conversion means changing text from upper case to lower case or vice versa. See Case. Case Folding Case folding means ignoring the differences between case variants of the same letter: upper-case, lower-case, and title-case. Emacs performs case folding by default in text search. See Lax Search. Character Characters form the contents of an Emacs buffer. Also, key sequences (q.v.) are usually made up of characters (though they may include other input events as well). See User Input. Character Folding Character folding means ignoring differences between similarly looking characters, such as between a, and a and á. Emacs performs character folding by default in text search. See Lax Search. Character Set Emacs supports a number of character sets, each of which represents a particular alphabet or script. See International. Character Terminal Click Event A click event is the kind of input event (q.v.) generated when you press a mouse button and release it without moving the mouse. See Mouse Buttons. Client Clipboard A clipboard is a buffer provided by the window system for transferring text between applications. On the X Window System, the clipboard is provided in addition to the primary selection (q.v.); on MS-Windows and Mac, the clipboard is used instead of the primary selection. See Clipboard. Coding System A coding system is an encoding for representing text characters in a file or in a stream of information. Emacs has the ability to convert text to or from a variety of coding systems when reading or writing it. See Coding Systems. Command A command is a Lisp function specially defined to be able to serve as a key binding in Emacs. When you type a key sequence (q.v.), its binding (q.v.) is looked up in the relevant keymaps (q.v.) to find the command to run. See Commands. Command History Command Name A command name is the name of a Lisp symbol that is a command (see Commands). You can invoke any command by its name using M-x (see Running Commands by Name). Comment A comment is text in a program which is intended only for humans reading the program, and which is specially marked so that it will be ignored when the program is loaded or compiled. Emacs offers special commands for creating, aligning and killing comments. See Comments. Common Lisp Common Lisp is a dialect of Lisp (q.v.) much larger and more powerful than Emacs Lisp. Emacs provides a subset of Common Lisp in the CL package. See Overview in Common Lisp Extensions. Compilation Compilation is the process of creating an executable program from source code. Emacs has commands for compiling files of Emacs Lisp code (see Byte Compilation in the Emacs Lisp Reference Manual) and programs in C and other languages (see Compilation). Complete Key A complete key is a key sequence that fully specifies one action to be performed by Emacs. For example, X and C-f and C-x m are complete keys. Complete keys derive their meanings from being bound (q.v.) to commands (q.v.). Thus, X is conventionally bound to a command to insert ‘X’ in the buffer; C-x m is conventionally bound to a command to begin composing a mail message. See Keys. Completion Completion is what Emacs does when it automatically expands an abbreviation for a name into the entire name. Completion is done for minibuffer (q.v.) arguments when the set of possible valid inputs is known; for example, on command names, buffer names, and file names. Completion usually occurs when TAB, SPC or RET is typed. See Completion. Continuation Line When a line of text is longer than the width of the window, it normally (but see Glossary---Truncation) takes up more than one screen line when displayed. We say that the text line is continued, and all screen lines used for it after the first are called continuation lines. See Continuation Lines. A related Emacs feature is filling (q.v.). Control Character A control character is a character that you type by holding down the Ctrl key. Some control characters also have their own keys, so that you can type them without using Ctrl. For example, RET, TAB, ESC and DEL are all control characters. See User Input. Copyleft A copyleft is a notice giving the public legal permission to redistribute and modify a program or other work of art, but requiring modified versions to carry similar permission. Copyright is normally used to keep users divided and helpless; with copyleft we turn that around to empower users and encourage them to cooperate. The particular form of copyleft used by the GNU project is called the GNU General Public License. See Copying. Ctrl The Ctrl or control key is what you hold down in order to enter a control character (q.v.). See Glossary---C-. Current Buffer The current buffer in Emacs is the Emacs buffer on which most editing commands operate. You can select any Emacs buffer as the current one. See Buffers. Current Line The current line is the line that point is on (see Point). Current Paragraph The current paragraph is the paragraph that point is in. If point is between two paragraphs, the current paragraph is the one that follows point. See Paragraphs. Current Defun The current defun is the defun (q.v.) that point is in. If point is between defuns, the current defun is the one that follows point. See Defuns. Cursor The cursor is the rectangle on the screen which indicates the position (called point; q.v.) at which insertion and deletion takes place. The cursor is on or under the character that follows point. Often people speak of “the cursor” when, strictly speaking, they mean “point”. See Cursor. Customization Customization is making minor changes in the way Emacs works, to reflect your preferences or needs. It is often done by setting variables (see Variables) or faces (see Face Customization), or by rebinding key sequences (see Keymaps). Cut and Paste See Glossary---Killing, and Glossary---Yanking. Daemon A daemon is a standard term for a system-level process that runs in the background. Daemons are often started when the system first starts up. When Emacs runs in daemon-mode, it runs in the background and does not open a display. You can then connect to it with the emacsclient program. See Emacs Server. Default Argument The default for an argument is the value that will be assumed if you do not specify one. When the minibuffer is used to read an argument, the default argument is used if you just type RET. See Minibuffer. Default A default is the value that is used for a certain purpose when you do not explicitly specify a value to use. Default Directory When you specify a file name that does not start with ‘/’ or ‘~’, it is interpreted relative to the current buffer’s default directory. (On MS systems, file names that start with a drive letter ‘x:’ are treated as absolute, not relative.) See Default Directory. Defun A defun is a major definition at the top level in a program. The name “defun” comes from Lisp, where most such definitions use the construct defun. See Defuns. DEL DEL is a character that runs the command to delete one character of text before the cursor. It is typically either the Delete key or the BACKSPACE key, whichever one is easy to type. See DEL. Deletion Deletion means erasing text without copying it into the kill ring (q.v.). The alternative is killing (q.v.). See Deletion. Deletion of Files Deleting a file means erasing it from the file system. (Note that some systems use the concept of a trash can, or recycle bin, to allow you to undelete files.) See Miscellaneous File Operations. Deletion of Messages Deleting a message (in Rmail, and other mail clients) means flagging it to be eliminated from your mail file. Until you expunge (q.v.) the Rmail file, you can still undelete the messages you have deleted. See Rmail Deletion. Deletion of Windows Deleting a window means eliminating it from the screen. Other windows expand to use up the space. The text that was in the window is not lost, and you can create a new window with the same dimensions as the old if you wish. See Windows. Directory File directories are named collections in the file system, within which you can place individual files or subdirectories. They are sometimes referred to as “folders”. See Directories. Directory Local Variable A directory local variable is a local variable (q.v.) that applies to all the files within a certain directory. See Directory Variables. Dired Dired is the Emacs facility that displays the contents of a file directory and allows you to “edit the directory”, performing operations on the files in the directory. See Dired. Disabled Command A disabled command is one that you may not run without special confirmation. The usual reason for disabling a command is that it is confusing for beginning users. See Disabling. Down Event Short for “button down event” (q.v.). Drag Event A drag event is the kind of input event (q.v.) generated when you press a mouse button, move the mouse, and then release the button. See Mouse Buttons. Dribble File A dribble file is a file into which Emacs writes all the characters that you type on the keyboard. Dribble files can be used to make a record for debugging Emacs bugs. Emacs does not make a dribble file unless you tell it to. See Bugs. Echo Area The echo area is the bottom line of the screen, used for echoing the arguments to commands, for asking questions, and showing brief messages (including error messages). The messages are stored in the buffer *Messages* so you can review them later. See Echo Area. Echoing Echoing is acknowledging the receipt of input events by displaying them (in the echo area). Emacs never echoes single-character key sequences; longer key sequences echo only if you pause while typing them. Electric We say that a character is electric if it is normally self-inserting (q.v.), but the current major mode (q.v.) redefines it to do something else as well. For example, some programming language major modes define particular delimiter characters to reindent the line, or insert one or more newlines in addition to self-insertion. End Of Line End of line is a character or a sequence of characters that indicate the end of a text line. On GNU and Unix systems, this is a newline (q.v.), but other systems have other conventions. See end-of-line. Emacs can recognize several end-of-line conventions in files and convert between them. Environment Variable An environment variable is one of a collection of variables stored by the operating system, each one having a name and a value. Emacs can access environment variables set by its parent shell, and it can set variables in the environment it passes to programs it invokes. See Environment. EOL Error An error occurs when an Emacs command cannot execute in the current circumstances. When an error occurs, execution of the command stops (unless the command has been programmed to do otherwise) and Emacs reports the error by displaying an error message (q.v.). Error Message An error message is output displayed by Emacs when you ask it to do something impossible (such as, killing text forward when point is at the end of the buffer), or when a command malfunctions in some way. Such messages appear in the echo area, accompanied by a beep. ESC ESC is a character used as a prefix for typing Meta characters on keyboards lacking a META key. Unlike the META key (which, like the SHIFT key, is held down while another character is typed), you press the ESC key as you would press a letter key, and it applies to the next character you type. Expression Expunging Expunging an Rmail, Gnus newsgroup, or Dired buffer is an operation that truly discards the messages or files you have previously flagged for deletion. Face A face is a style of displaying characters. It specifies attributes such as font family and size, foreground and background colors, underline and strike-through, background stipple, etc. Emacs provides features to associate specific faces with portions of buffer text, in order to display that text as specified by the face attributes. See Faces. File Local Variable A file local variable is a local variable (q.v.) specified in a given file. See File Variables, and Glossary---Directory Local Variable. File Locking Emacs uses file locking to notice when two different users start to edit one file at the same time. See Interlocking. File Name A file name is a name that refers to a file. File names may be relative or absolute; the meaning of a relative file name depends on the current directory, but an absolute file name refers to the same file regardless of which directory is current. On GNU and Unix systems, an absolute file name starts with a slash (the root directory) or with ‘~/’ or ‘~user/’ (a home directory). On MS-Windows/MS-DOS, an absolute file name can also start with a drive letter and a colon, e.g., ‘d:’. Some people use the term “pathname” for file names, but we do not; we use the word “path” only in the term “search path” (q.v.). File-Name Component A file-name component names a file directly within a particular directory. On GNU and Unix systems, a file name is a sequence of file-name components, separated by slashes. For example, foo/bar is a file name containing two components, ‘foo’ and ‘bar’; it refers to the file named ‘bar’ in the directory named ‘foo’ in the current directory. MS-DOS/MS-Windows file names can also use backslashes to separate components, as in foo\bar. Fill Prefix The fill prefix is a string that should be expected at the beginning of each line when filling is done. It is not regarded as part of the text to be filled. See Filling. Filling Filling text means adjusting the position of line-breaks to shift text between consecutive lines, so that all the lines are approximately the same length. See Filling. Some other editors call this feature “line wrapping”. Font Lock Font Lock is a mode that highlights parts of buffer text in different faces, according to the syntax. Some other editors refer to this as “syntax highlighting”. For example, all comments (q.v.) might be colored red. See Font Lock. Fontset A fontset is a named collection of fonts. A fontset specification lists character sets and which font to use to display each of them. Fontsets make it easy to change several fonts at once by specifying the name of a fontset, rather than changing each font separately. See Fontsets. Formfeed Character See Glossary---Page. Frame A frame is a rectangular cluster of Emacs windows. Emacs starts out with one frame, but you can create more. You can subdivide each frame into Emacs windows (q.v.). When you are using a window system (q.v.), more than one frame can be visible at the same time. See Frames. Some other editors use the term “window” for this, but in Emacs a window means something else. Free Software Free software is software that gives you the freedom to share, study and modify it. Emacs is free software, part of the GNU project (q.v.), and distributed under a copyleft (q.v.) license called the GNU General Public License. See Copying. Free Software Foundation The Free Software Foundation (FSF) is a charitable foundation dedicated to promoting the development of free software (q.v.). For more information, see the FSF website. Fringe On a graphical display (q.v.), there’s a narrow portion of the frame (q.v.) between the text area and the window’s border. These “fringes” are used to display symbols that provide information about the buffer text (see Fringes). Emacs displays the fringe using a special face (q.v.) called fringe. See fringe. FSF FTP FTP is an acronym for File Transfer Protocol. This is one standard method for retrieving remote files (q.v.). Function Key A function key is a key on the keyboard that sends input but does not correspond to any character. See Function Keys. Global Global means “independent of the current environment; in effect throughout Emacs”. It is the opposite of local (q.v.). Particular examples of the use of “global” appear below. Global Abbrev A global definition of an abbrev (q.v.) is effective in all major modes that do not have local (q.v.) definitions for the same abbrev. See Abbrevs. Global Keymap The global keymap (q.v.) contains key bindings that are in effect everywhere, except when overridden by local key bindings in a major mode’s local keymap (q.v.). See Keymaps. Global Mark Ring The global mark ring records the series of buffers you have recently set a mark (q.v.) in. In many cases you can use this to backtrack through buffers you have been editing, or in which you have found tags (see Glossary---Tags Table). See Global Mark Ring. Global Substitution Global substitution means replacing each occurrence of one string by another string throughout a large amount of text. See Replace. Global Variable The global value of a variable (q.v.) takes effect in all buffers that do not have their own local (q.v.) values for the variable. See Variables. GNU GNU is a recursive acronym for GNU’s Not Unix, and it refers to a Unix-compatible operating system which is free software (q.v.). See Manifesto. GNU is normally used with Linux as the kernel since Linux works better than the GNU kernel. For more information, see the GNU website. Graphic Character Graphic characters are those assigned pictorial images rather than just names. All the non-Meta (q.v.) characters except for the Control (q.v.) characters are graphic characters. These include letters, digits, punctuation, and spaces; they do not include RET or ESC. In Emacs, typing a graphic character inserts that character (in ordinary editing modes). See Inserting Text. Graphical Display A graphical display is one that can display images and multiple fonts. Usually it also has a window system (q.v.). Highlighting Highlighting text means displaying it with a different foreground and/or background color to make it stand out from the rest of the text in the buffer. Emacs uses highlighting in several ways. It highlights the region whenever it is active (see Mark). Incremental search also highlights matches (see Incremental Search). See Glossary---Font Lock. Hardcopy Hardcopy means printed output. Emacs has various commands for printing the contents of Emacs buffers. See Printing. HELP HELP is the Emacs name for C-h or F1. You can type HELP at any time to ask what options you have, or to ask what a command does. See Help. Help Echo Help echo is a short message displayed in the echo area (q.v.) when the mouse pointer is located on portions of display that require some explanations. Emacs displays help echo for menu items, parts of the mode line, tool-bar buttons, etc. On graphical displays, the messages can be displayed as tooltips (q.v.). See Tooltips. Home Directory Your home directory contains your personal files. On a multi-user GNU or Unix system, each user has his or her own home directory. When you start a new login session, your home directory is the default directory in which to start. A standard shorthand for your home directory is ‘~’. Similarly, ‘~user’ represents the home directory of some other user. Hook A hook is a list of functions to be called on specific occasions, such as saving a buffer in a file, major mode activation, etc. By customizing the various hooks, you can modify Emacs’s behavior without changing any of its code. See Hooks. Hyper Hyper is the name of a modifier bit that a keyboard input character may have. To make a character Hyper, type it while holding down the Hyper key. Such characters are given names that start with Hyper- (usually written H- for short). See User Input. Iff “Iff” means “if and only if”. This terminology comes from mathematics. Try to avoid using this term in documentation, since many are unfamiliar with it and mistake it for a typo. Inbox An inbox is a file in which mail is delivered by the operating system. Rmail transfers mail from inboxes to Rmail files in which the mail is then stored permanently or until explicitly deleted. See Rmail Inbox. Incremental Search Emacs provides an incremental search facility, whereby Emacs begins searching for a string as soon as you type the first character. As you type more characters, it refines the search. See Incremental Search. Indentation Indentation means blank space at the beginning of a line. Most programming languages have conventions for using indentation to illuminate the structure of the program, and Emacs has special commands to adjust indentation. See Indentation. Indirect Buffer An indirect buffer is a buffer that shares the text of another buffer, called its base buffer (q.v.). See Indirect Buffers. Info Info is the hypertext format used by the GNU project for writing documentation. Input Event An input event represents, within Emacs, one action taken by the user on the terminal. Input events include typing characters, typing function keys, pressing or releasing mouse buttons, and switching between Emacs frames. See User Input. Input Method An input method is a system for entering non-ASCII text characters by typing sequences of ASCII characters (q.v.). See Input Methods. Insertion Insertion means adding text into the buffer, either from the keyboard or from some other place in Emacs. Interlocking Isearch Justification Justification means adding extra spaces within lines of text in order to adjust the position of the text edges. See Fill Commands. Key Binding Keyboard Macro Keyboard macros are a way of defining new Emacs commands from sequences of existing ones, with no need to write a Lisp program. You can use a macro to record a sequence of commands, then play them back as many times as you like. See Keyboard Macros. Keyboard Shortcut A keyboard shortcut is a key sequence (q.v.) that invokes a command. What some programs call “assigning a keyboard shortcut”, Emacs calls “binding a key sequence”. See Glossary---Binding. Key Sequence A key sequence (key, for short) is a sequence of input events (q.v.) that are meaningful as a single unit. If the key sequence is enough to specify one action, it is a complete key (q.v.); if it is not enough, it is a prefix key (q.v.). See Keys. Keymap The keymap is the data structure that records the bindings (q.v.) of key sequences to the commands that they run. For example, the global keymap binds the character C-n to the command function next-line. See Keymaps. Keyboard Translation Table The keyboard translation table is an array that translates the character codes that come from the terminal into the character codes that make up key sequences. Kill Ring The kill ring is where all text you have killed (see Glossary---Killing) recently is saved. You can reinsert any of the killed text still in the ring; this is called yanking (q.v.). See Yanking. Killing Killing means erasing text and saving it on the kill ring so it can be yanked (q.v.) later. Some other systems call this “cutting”. Most Emacs commands that erase text perform killing, as opposed to deletion (q.v.). See Killing. Killing a Job Killing a job (such as, an invocation of Emacs) means making it cease to exist. Any data within it, if not saved in a file, is lost. See Exiting. Language Environment Your choice of language environment specifies defaults for the input method (q.v.) and coding system (q.v.). See Language Environments. These defaults are relevant if you edit non-ASCII text (see International). Line Wrapping Lisp Lisp is a programming language. Most of Emacs is written in a dialect of Lisp, called Emacs Lisp, which is extended with special features that make it especially suitable for text editing tasks. List A list is, approximately, a text string beginning with an open parenthesis and ending with the matching close parenthesis. In C mode and other non-Lisp modes, groupings surrounded by other kinds of matched delimiters appropriate to the language, such as braces, are also considered lists. Emacs has special commands for many operations on lists. See Moving by Parens. Local Local means “in effect only in a particular context”; the relevant kind of context is a particular function execution, a particular buffer, or a particular major mode. It is the opposite of “global” (q.v.). Specific uses of “local” in Emacs terminology appear below. Local Abbrev A local abbrev definition is effective only if a particular major mode is selected. In that major mode, it overrides any global definition for the same abbrev. See Abbrevs. Local Keymap A local keymap is used in a particular major mode; the key bindings (q.v.) in the current local keymap override global bindings of the same key sequences. See Keymaps. Local Variable A local value of a variable (q.v.) applies to only one buffer. See Locals. M- M- in the name of a character is an abbreviation for Meta, one of the modifier keys that can accompany any character. See M-. M-C- M-C- in the name of a character is an abbreviation for Control-Meta; it means the same thing as C-M- (q.v.). M-x M-x is the key sequence that is used to call an Emacs command by name. This is how you run commands that are not bound to key sequences. See Running Commands by Name. Mail Mail means messages sent from one user to another through the computer system, to be read at the recipient’s convenience. Emacs has commands for composing and sending mail, and for reading and editing the mail you have received. See Sending Mail. See Rmail, for one way to read mail with Emacs. Mail Composition Method A mail composition method is a program runnable within Emacs for editing and sending a mail message. Emacs lets you select from several alternative mail composition methods. See Mail Methods. Major Mode The Emacs major modes are a mutually exclusive set of options, each of which configures Emacs for editing a certain sort of text. Ideally, each programming language has its own major mode. See Major Modes. Margin The space between the usable part of a window (including the fringe) and the window edge. Mark The mark points to a position in the text. It specifies one end of the region (q.v.), point being the other end. Many commands operate on all the text from point to the mark. Each buffer has its own mark. See Mark. Mark Ring The mark ring is used to hold several recent previous locations of the mark, in case you want to move back to them. Each buffer has its own mark ring; in addition, there is a single global mark ring (q.v.). See Mark Ring. Menu Bar The menu bar is a line at the top of an Emacs frame. It contains words you can click on with the mouse to bring up menus, or you can use a keyboard interface to navigate it. See Menu Bars. Message See Glossary---Mail. Meta Meta is the name of a modifier bit which you can use in a command character. To enter a meta character, you hold down the Meta key while typing the character. We refer to such characters with names that start with Meta- (usually written M- for short). For example, M-< is typed by holding down Meta and at the same time typing < (which itself is done, on most terminals, by holding down SHIFT and typing ,). See Meta. On some terminals, the Meta key is actually labeled Alt or Edit. Meta Character A Meta character is one whose character code includes the Meta bit. Minibuffer The minibuffer is the window that appears when necessary inside the echo area (q.v.), used for reading arguments to commands. See Minibuffer. Minibuffer History The minibuffer history records the text you have specified in the past for minibuffer arguments, so you can conveniently use the same text again. See Minibuffer History. Minor Mode A minor mode is an optional feature of Emacs, which can be switched on or off independently of all other features. Each minor mode has a command to turn it on or off. Some minor modes are global (q.v.), and some are local (q.v.). See Minor Modes. Minor Mode Keymap A minor mode keymap is a keymap that belongs to a minor mode and is active when that mode is enabled. Minor mode keymaps take precedence over the buffer’s local keymap, just as the local keymap takes precedence over the global keymap. See Keymaps. Mode Line The mode line is the line at the bottom of each window (q.v.), giving status information on the buffer displayed in that window. See Mode Line. Modified Buffer A buffer (q.v.) is modified if its text has been changed since the last time the buffer was saved (or since it was created, if it has never been saved). See Saving. Moving Text Moving text means erasing it from one place and inserting it in another. The usual way to move text is by killing (q.v.) it and then yanking (q.v.) it. See Killing. MULE Prior to Emacs 23, MULE was the name of a software package which provided a MULtilingual Enhancement to Emacs, by adding support for multiple character sets (q.v.). MULE was later integrated into Emacs, and much of it was replaced when Emacs gained internal Unicode support in version 23. Some parts of Emacs that deal with character set support still use the MULE name. See International. Multibyte Character A multibyte character is a character that takes up several bytes in a buffer. Emacs uses multibyte characters to represent non-ASCII text, since the number of non-ASCII characters is much more than 256. See International Characters. Named Mark A named mark is a register (q.v.), in its role of recording a location in text so that you can move point to that location. See Registers. Narrowing Narrowing means creating a restriction (q.v.) that limits editing in the current buffer to only a part of the text. Text outside that part is inaccessible for editing (or viewing) until the boundaries are widened again, but it is still there, and saving the file saves it all. See Narrowing. Newline Control-J characters in the buffer terminate lines of text and are therefore also called newlines. See Glossary---End Of Line. nil nil is a value usually interpreted as a logical “false”. Its opposite is t, interpreted as “true”. Numeric Argument A numeric argument is a number, specified before a command, to change the effect of the command. Often the numeric argument serves as a repeat count. See Arguments. Overwrite Mode Overwrite mode is a minor mode. When it is enabled, ordinary text characters replace the existing text after point rather than pushing it to one side. See Minor Modes. Package A package is a collection of Lisp code that you download and automatically install from within Emacs. Packages provide a convenient way to add new features. See Packages. Page A page is a unit of text, delimited by formfeed characters (ASCII control-L, code 014) at the beginning of a line. Some Emacs commands are provided for moving over and operating on pages. See Pages. Paragraph Paragraphs are the medium-size unit of human-language text. There are special Emacs commands for moving over and operating on paragraphs. See Paragraphs. Parsing We say that certain Emacs commands parse words or expressions in the text being edited. Really, all they know how to do is find the other end of a word or expression. Point Point is the place in the buffer at which insertion and deletion occur. Point is considered to be between two characters, not at one character. The terminal’s cursor (q.v.) indicates the location of point. See Point. Prefix Argument Prefix Key A prefix key is a key sequence (q.v.) whose sole function is to introduce a set of longer key sequences. C-x is an example of prefix key; any two-character sequence starting with C-x is therefore a legitimate key sequence. See Keys. Primary Selection The primary selection is one particular X selection (q.v.); it is the selection that most X applications use for transferring text to and from other applications. The Emacs kill commands set the primary selection and the yank command uses the primary selection when appropriate. See Killing. Prompt A prompt is text used to ask you for input. Displaying a prompt is called prompting. Emacs prompts always appear in the echo area (q.v.). One kind of prompting happens when the minibuffer is used to read an argument (see Minibuffer); the echoing that happens when you pause in the middle of typing a multi-character key sequence is also a kind of prompting (see Echo Area). Query-Replace Query-replace is an interactive string replacement feature provided by Emacs. See Query Replace. Quitting Quitting means canceling a partially typed command or a running command, using C-g (or C-BREAK on MS-DOS). See Quitting. Quoting Quoting means depriving a character of its usual special significance. The most common kind of quoting in Emacs is with C-q. What constitutes special significance depends on the context and on convention. For example, an ordinary character as an Emacs command inserts itself; so in this context, a special character is any character that does not normally insert itself (such as DEL, for example), and quoting it makes it insert itself as if it were not special. Not all contexts allow quoting. See Quoting. Quoting File Names Quoting a file name turns off the special significance of constructs such as ‘’, ‘~’ and ‘:’. See Quoted File Names.

A read-only buffer is one whose text you are not allowed to change. Normally Emacs makes buffers read-only when they contain text which has a special significance to Emacs; for example, Dired buffers. Visiting a file that is write-protected also makes a read-only buffer. See Buffers.

Rectangle

A rectangle consists of the text in a given range of columns on a given range of lines. Normally you specify a rectangle by putting point at one corner and putting the mark at the diagonally opposite corner. See Rectangles.

Recursive Editing Level

A recursive editing level is a state in which part of the execution of a command involves asking you to edit some text. This text may or may not be the same as the text to which the command was applied. The mode line indicates recursive editing levels with square brackets (‘[’ and ‘]’). See Recursive Edit.

Redisplay

Redisplay is the process of correcting the image on the screen to correspond to changes that have been made in the text being edited. See Redisplay.

Regexp
Region

The region is the text between point (q.v.) and the mark (q.v.). Many commands operate on the text of the region. See Region.

Register

Registers are named slots in which text, buffer positions, or rectangles can be saved for later use. See Registers. A related Emacs feature is bookmarks (q.v.).

Regular Expression

A regular expression is a pattern that can match various text strings; for example, ‘a[0-9]+’ matches ‘a’ followed by one or more digits. See Regexps.

Remote File

A remote file is a file that is stored on a system other than your own. Emacs can access files on other computers provided that they are connected to the same network as your machine, and (obviously) that you have a supported method to gain access to those files. See Remote Files.

Repeat Count
Replacement
Restriction

A buffer’s restriction is the amount of text, at the beginning or the end of the buffer, that is temporarily inaccessible. Giving a buffer a nonzero amount of restriction is called narrowing (q.v.); removing a restriction is called widening (q.v.). See Narrowing.

RET

RET is a character that in Emacs runs the command to insert a newline into the text. It is also used to terminate most arguments read in the minibuffer (q.v.). See Return.

Reverting

Reverting means returning to the original state. Emacs lets you revert a buffer by re-reading its file from disk. See Reverting.

Saving

Saving a buffer means copying its text into the file that was visited (q.v.) in that buffer. This is the way text in files actually gets changed by your Emacs editing. See Saving.

Scroll Bar

A scroll bar is a tall thin hollow box that appears at the side of a window. You can use mouse commands in the scroll bar to scroll the window. The scroll bar feature is supported only under windowing systems. See Scroll Bars.

Scrolling

Scrolling means shifting the text in the Emacs window so as to see a different part of the buffer. See Scrolling.

Searching

Searching means moving point to the next occurrence of a specified string or the next match for a specified regular expression. See Search.

Search Path

A search path is a list of directory names, to be used for searching for files for certain purposes. For example, the variable load-path` holds a search path for finding Lisp library files. See Lisp Libraries.

Secondary Selection

The secondary selection is one particular X selection (q.v.); some X applications can use it for transferring text to and from other applications. Emacs has special mouse commands for transferring text using the secondary selection. See Secondary Selection.

Selected Frame

The selected frame is the one your input currently operates on. See Frames.

Selected Window

The selected window is the one your input currently operates on. See Basic Window.

Selecting a Buffer

Selecting a buffer means making it the current (q.v.) buffer. See Select Buffer.

Selection

Windowing systems allow an application program to specify selections whose values are text. A program can also read the selections that other programs have set up. This is the principal way of transferring text between window applications. Emacs has commands to work with the primary (q.v.) selection and the secondary (q.v.) selection, and also with the clipboard (q.v.).

Self-Documentation

Self-documentation is the feature of Emacs that can tell you what any command does, or give you a list of all commands related to a topic you specify. You ask for self-documentation with the help character, C-h. See Help.

Self-Inserting Character

A character is self-inserting if typing that character inserts that character in the buffer. Ordinary printing and whitespace characters are self-inserting in Emacs, except in certain special major modes.

Sentences

Emacs has commands for moving by or killing by sentences. See Sentences.

Server

Within Emacs, you can start a “server” process, which listens for connections from “clients”. This offers a faster alternative to starting several Emacs instances. See Emacs Server, and Glossary---Daemon.

Sexp

A sexp (short for “s-expression”) is the basic syntactic unit of Lisp in its textual form: either a list, or Lisp atom. Sexps are also the balanced expressions (q.v.) of the Lisp language; this is why the commands for editing balanced expressions have ‘sexp’ in their name. See Sexps.

Simultaneous Editing

Simultaneous editing means two users modifying the same file at once. Simultaneous editing, if not detected, can cause one user to lose his or her work. Emacs detects all cases of simultaneous editing, and warns one of the users to investigate. See Simultaneous Editing.

SPC

SPC is the space character, which you enter by pressing the space bar.

Speedbar

The speedbar is a special tall frame that provides fast access to Emacs buffers, functions within those buffers, Info nodes, and other interesting parts of text within Emacs. See Speedbar.

Spell Checking

Spell checking means checking correctness of the written form of each one of the words in a text. Emacs can use various external spelling-checker programs to check the spelling of parts of a buffer via a convenient user interface. See Spelling.

String

A string is a kind of Lisp data object that contains a sequence of characters. Many Emacs variables are intended to have strings as values. The Lisp syntax for a string consists of the characters in the string with a ‘"’ before and another ‘"’ after. A ‘"’ that is part of the string must be written as ‘\"’ and a ‘\’ that is part of the string must be written as ‘\\’. All other characters, including newline, can be included just by writing them inside the string; however, backslash sequences as in C, such as ‘\n’ for newline or ‘\241’ using an octal character code, are allowed as well.

String Substitution
Syntax Highlighting
Syntax Table

The syntax table tells Emacs which characters are part of a word, which characters balance each other like parentheses, etc. See Syntax Tables in The Emacs Lisp Reference Manual.

Super

Super is the name of a modifier bit that a keyboard input character may have. To make a character Super, type it while holding down the SUPER key. Such characters are given names that start with Super- (usually written s- for short). See User Input.

Suspending

Suspending Emacs means stopping it temporarily and returning control to its parent process, which is usually a shell. Unlike killing a job (q.v.), you can later resume the suspended Emacs job without losing your buffers, unsaved edits, undo history, etc. See Exiting.

TAB

TAB is the tab character. In Emacs it is typically used for indentation or completion.

Tags Table

A tags table is a file that serves as an index to the function definitions in one or more other files. See Tags Tables.

Termscript File

A termscript file contains a record of all characters sent by Emacs to the terminal. It is used for tracking down bugs in Emacs redisplay. Emacs does not make a termscript file unless you tell it to. See Bugs.

Text

“Text” has two meanings (see Text):

• Data consisting of a sequence of characters, as opposed to binary numbers, executable programs, and the like. The basic contents of an Emacs buffer (aside from the text properties, q.v.) are always text in this sense.
• Data consisting of written human language (as opposed to programs), or following the stylistic conventions of human language.
Text Terminal

A text terminal, or character terminal, is a display that is limited to displaying text in character units. Such a terminal cannot control individual pixels it displays. Emacs supports a subset of display features on text terminals.

Text Properties

Text properties are annotations recorded for particular characters in the buffer. Images in the buffer are recorded as text properties; they also specify formatting information. See Editing Format Info.

Theme

A theme is a set of customizations (q.v.) that give Emacs a particular appearance or behavior. For example, you might use a theme for your favorite set of faces (q.v.).

Tool Bar

The tool bar is a line (sometimes multiple lines) of icons at the top of an Emacs frame. Clicking on one of these icons executes a command. You can think of this as a graphical relative of the menu bar (q.v.). See Tool Bars.

Tooltips

Tooltips are small windows displaying a help echo (q.v.) text, which explains parts of the display, lists useful options available via mouse clicks, etc. See Tooltips.

Top Level

Top level is the normal state of Emacs, in which you are editing the text of the file you have visited. You are at top level whenever you are not in a recursive editing level (q.v.) or the minibuffer (q.v.), and not in the middle of a command. You can get back to top level by aborting (q.v.) and quitting (q.v.). See Quitting.

Transient Mark Mode

The default behavior of the mark (q.v.) and region (q.v.), in which setting the mark activates it and highlights the region, is called Transient Mark mode. In GNU Emacs 23 and onwards, it is enabled by default. See Disabled Transient Mark.

Transposition

Transposing two units of text means putting each one into the place formerly occupied by the other. There are Emacs commands to transpose two adjacent characters, words, balanced expressions (q.v.) or lines (see Transpose).

Trash Can
Truncation

Truncating text lines in the display means leaving out any text on a line that does not fit within the right margin of the window displaying it. See Truncation, and Glossary---Continuation Line.

TTY
Undoing

Undoing means making your previous editing go in reverse, bringing back the text that existed earlier in the editing session. See Undo.

Unix

Unix is a class of multi-user computer operating systems with a long history. There are several implementations today. The GNU project (q.v.) aims to develop a complete Unix-like operating system that is free software (q.v.).

User Option

A user option is a face (q.v.) or a variable (q.v.) that exists so that you can customize Emacs by setting it to a new value. See Easy Customization.

Variable

A variable is an object in Lisp that can store an arbitrary value. Emacs uses some variables for internal purposes, and has others (known as “user options”; q.v.) just so that you can set their values to control the behavior of Emacs. The variables used in Emacs that you are likely to be interested in are listed in the Variables Index in this manual (see Variable Index). See Variables, for information on variables.

Version Control

Version control systems keep track of multiple versions of a source file. They provide a more powerful alternative to keeping backup files (q.v.). See Version Control.

Visiting

Visiting a file means loading its contents into a buffer (q.v.) where they can be edited. See Visiting.

Whitespace

Whitespace is any run of consecutive formatting characters (space, tab, newline, and backspace).

Widening

Widening is removing any restriction (q.v.) on the current buffer; it is the opposite of narrowing (q.v.). See Narrowing.

Window

Emacs divides a frame (q.v.) into one or more windows, each of which can display the contents of one buffer (q.v.) at any time. See Screen, for basic information on how Emacs uses the screen. See Windows, for commands to control the use of windows. Some other editors use the term “window” for what we call a “frame” (q.v.) in Emacs.

Window System

A window system is software that operates on a graphical display (q.v.), to subdivide the screen so that multiple applications can have their] own windows at the same time. All modern operating systems include a window system.

Word Abbrev
Word Search

Word search is searching for a sequence of words, considering the punctuation between them as insignificant. See Word Search.

Yanking

Yanking means reinserting text previously killed (q.v.). It can be used to undo a mistaken kill, or for copying or moving text. Some other systems call this “pasting”. See Yanking.

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