An abbrev is a text string which expands into a different text string when present in the buffer. For example, you might define a short word as an abbrev for a long phrase that you want to insert frequently. See Abbrevs.
Aborting means getting out of a recursive edit (q.v.). You can use the commands C-] and M-x top-level for this. See Quitting.
Auto Fill mode is a minor mode in which text you insert is automatically broken into lines of fixed width. See Filling.
Auto saving means that Emacs automatically stores the contents of an Emacs buffer in a specially-named file so the information will not be lost if the buffer is lost due to a system error or user error. See Auto Save.
A backup file records the contents that a file had before the current editing session. Emacs creates backup files automatically to help you track down or cancel changes you later regret. See Backup.
Emacs can balance parentheses manually or automatically. Manual balancing is done by the commands to move over balanced expressions (see Lists). Automatic balancing is done by blinking the parenthesis that matches one just inserted (see Matching Parens).
To bind a key is to change its binding (q.v.). See Rebinding.
A key gets its meaning in Emacs by having a binding which is a command (q.v.), a Lisp function that is run when the key is typed. See Binding. Customization often involves rebinding a character to a different command function. The bindings of all keys are recorded in the keymaps (q.v.). See Keymaps.
Blank lines are lines that contain only whitespace. Emacs has several commands for operating on the blank lines in a buffer.
The buffer is the basic editing unit; one buffer corresponds to one piece of text being edited. You can have several buffers, but at any time you are editing only one, the ‘selected’ buffer, though several buffers can be visible when you are using multiple windows. See Buffers.
Emacs keeps a buffer selection history which records how recently each Emacs buffer was selected. Emacs uses this list when choosing a buffer to select. See Buffers.
‘C’ in the name of a character is an abbreviation for Control. See C-.
‘C-M-’ in the name of a character is an abbreviation for Control-Meta. See C-M-.
Case conversion means changing text from upper case to lower case or vice versa. See Case, for the commands for case conversion.
Characters form the contents of an Emacs buffer; also, Emacs commands are invoked by keys (q.v.), which are sequences of one or more characters. See Keystrokes.
A command is a Lisp function specially defined to be able to serve as a key binding in Emacs. When you type a key (q.v.), Emacs looks up its binding (q.v.) in the relevant keymaps (q.v.) to find the command to run. See Commands.
A command name is the name of a Lisp symbol which is a command (see Commands). You can invoke any command by its name using M-x (see M-x).
A comment is text in a program which is intended only for the people reading the program, and is marked specially 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.
Compilation is the process of creating an executable program from source code. Emacs has commands for compiling files of Emacs Lisp code (see Lisp Libraries) and programs in C and other languages (see Compilation).
A complete key is a character or sequence of characters which, when typed by the user, fully specifies one action to be performed by Emacs. For example, X and Control-f and Control-x m are keys. 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 Keystrokes.
When Emacs automatically fills an abbreviation for a name into the entire name, that process is called completion. 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 occurs when you type TAB, SPC, or RET. See Completion.
When a line of text is longer than the width of the frame, it 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 Basic Editing.
ASCII characters with octal codes 0 through 037, and also code 0177, do not have graphic images assigned to them. These are the control characters. Any control character can be typed by holding down the CTRL key and typing some other character; some have special keys on the keyboard. RET, TAB, ESC, LFD, and DEL are all control characters. See Keystrokes.
A copyleft is a notice giving the public legal permission to redistribute a program or other work of art. Copylefts are used by leftists to enrich the public just as copyrights are used by rightists to gain power over the public.
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.
The line point is on (see Point).
The paragraph that point is in. If point is between paragraphs, the current paragraph is the one that follows point. See Paragraphs.
The defun (q.v.) that point is in. If point is between defuns, the current defun is the one that follows point. See Defuns.
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 Basic Editing.
Customization is making minor changes in the way Emacs works. It is often done by setting variables (see Variables) or by rebinding keys (see Keymaps).
The default for an argument is the value that is used if you do not specify one. When Emacs prompts you in the minibuffer for an argument, the default argument is used if you just type RET. See Minibuffer.
When you specify a file name that does not start with ‘/’ or ‘~’, it is interpreted relative to the current buffer’s default directory. See Default Directory.
A defun is a list at the top level of parenthesis or bracket structure
in a program. It is so named because most such lists in Lisp programs
are calls to the Lisp function defun. See Defuns.
The DEL character runs the command that deletes one character of text. See Basic Editing.
Deleting text means erasing it without saving it. Emacs deletes text only when it is expected not to be worth saving (all whitespace, or only one character). The alternative is killing (q.v.). See Deletion.
Deleting a file means removing it from the file system. See Misc File Ops.
Deleting a message means flagging it to be eliminated from your mail file. Until the mail file is expunged, you can undo this by undeleting the message.
When working under the multi-frame X-based version of SXEmacs, you can delete individual frames using the Close menu item from the File menu.
When you delete a subwindow of an Emacs frame, you eliminate it from the frame. Other windows expand to use up the space. The deleted window can never come back, but no actual text is lost. See Windows.
Files in the Unix file system are grouped into file directories. See Directories.
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.
A disabled command is one that you may not run without special confirmation. Commands are usually disabled because they are confusing for beginning users. See Disabling.
A file into which Emacs writes all the characters that the user types on the keyboard. Dribble files are used to make a record for debugging Emacs bugs. Emacs does not make a dribble file unless you tell it to. See Bugs.
The area at the bottom of the Emacs frame which is used for echoing the arguments to commands, for asking questions, and for printing brief messages (including error messages). See Echo Area.
Echoing refers to acknowledging the receipt of commands by displaying them (in the echo area). Emacs never echoes single-character keys; longer keys echo only if you pause while typing them.
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 printing an error message (q.v.). Type-ahead is discarded. Then Emacs is ready to read another editing command.
Error messages are single lines of output printed by Emacs when the user asks for something impossible to do (such as killing text forward when point is at the end of the buffer). They appear in the echo area, accompanied by a beep.
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), the ESC key is pressed and released, and applies to the next character typed.
The fill prefix is a string that Emacs enters at the beginning of each line when it performs filling. It is not regarded as part of the text to be filled. See Filling.
Filling text means moving text from line to line so that all the lines are approximately the same length. See Filling.
When running Emacs on a TTY terminal, “frame” means the terminal’s screen. When running Emacs under X, you can have multiple frames, each corresponding to a top-level X window and each looking like the screen on a TTY. Each frame contains one or more non-overlapping Emacs windows (possibly with associated scrollbars, under X), an echo area, and (under X) possibly a menubar, toolbar, and/or gutter.
Global means ‘independent of the current environment; in effect
throughout Emacs’. It is the opposite of local (q.v.).
Examples of the use of ‘global’ appear below.
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.
The global keymap (q.v.) contains key bindings that are in effect unless local key bindings in a major mode’s local keymap (q.v.) override them.See Keymaps.
Global substitution means replacing each occurrence of one string by another string through a large amount of text. See Replace.
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.
Graphic characters are those assigned pictorial images rather than just names. All the non-Meta (q.v.) characters except for the Control (q.v.) character 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 Basic Editing.
Grinding means adjusting the indentation in a program to fit the nesting structure. See Grinding.
Hardcopy means printed output. Emacs has commands for making printed listings of text in Emacs buffers. See Hardcopy.
You can type HELP at any time to ask what options you have, or to ask what any command does. HELP is really Control-h. See Help.
An inbox is a file in which mail is delivered by the operating system. Some mail handlers transfers mail from inboxes to mail files (q.v.) in which the mail is then stored permanently or until explicitly deleted.
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 features to help you set up the correct indentation. See Indentation.
Insertion means copying text into the buffer, either from the keyboard or from some other place in Emacs.
Justification means adding extra spaces to lines of text to make them come exactly to a specified width. See Justification.
Keyboard macros are a way of defining new Emacs commands from sequences of existing ones, with no need to write a Lisp program. See Keyboard Macros.
A key is a sequence of characters that, when input to Emacs, specify or begin to specify a single action for Emacs to perform. That is, the sequence is considered a single unit. If the key is enough to specify one action, it is a complete key (q.v.); if it is less than enough, it is a prefix key (q.v.). See Keystrokes.
The keymap is the data structure that records the bindings (q.v.) of
keys to the commands that they run. For example, the keymap binds the
character C-n to the command function next-line.
See Keymaps.
The kill ring is the place where all text you have killed recently is saved. You can re-insert any of the killed text still in the ring; this is called yanking (q.v.). See Yanking.
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 to erase text do killing, as opposed to deletion (q.v.). See Killing.
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.
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 Lists.
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. Local is the opposite of ‘global’ (q.v.). Specific uses of ‘local’ in Emacs terminology appear below.
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.
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 keys. See Keymaps.
A local value of a variable (q.v.) applies to only one buffer. See Locals.
M- in the name of a character is an abbreviation for META, one of the modifier keys that can accompany any character. See Keystrokes.
‘M-C-’ in the name of a character is an abbreviation for Control-Meta; it means the same thing as ‘C-M-’. 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-.
M-x is the key which is used to call an Emacs command by name. You use it to call commands that are not bound to keys. See M-x.
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.
The 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.
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 the whole region, that is, all the text from point to the mark. See Mark.
The mark ring is used to hold several recent previous locations of the mark, just in case you want to move back to them. See Mark Ring.
See ‘mail’.
Meta is the name of a modifier bit which a command character may have. It is present in a character if the character is typed with the META key held down. Such characters are given names that start with Meta-. For example, Meta-< 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.
A Meta character is one whose character code includes the Meta bit.
The minibuffer is the window that Emacs displays inside the echo area (q.v.) when it prompts you for arguments to commands. See Minibuffer.
A minor mode is an optional feature of Emacs which can be switched on or off independent of the major mode. Each minor mode has a command to turn it on or off. See Minor Modes.
The mode line is the line at the bottom of each text window (q.v.), which gives status information on the buffer displayed in that window. See Mode Line.
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 means erasing it from one place and inserting it in another. This is done by killing (q.v.) and then yanking (q.v.). See Killing.
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 means creating a restriction (q.v.) that limits editing in the current buffer to only a part of the text in the buffer. Text outside that part is inaccessible to the user until the boundaries are widened again, but it is still there, and saving the file saves the invisible text. See Narrowing.
LFD characters in the buffer terminate lines of text and are called newlines. See Newline.
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.
An option is a variable (q.v.) that allows you to customize Emacs by giving it a new value. See Variables.
Overwrite mode is a minor mode. When it is enabled, ordinary text characters replace the existing text after point rather than pushing it to the right. See Minor Modes.
A page is a unit of text, delimited by formfeed characters (ASCII Control-L, code 014) coming at the beginning of a line. Some Emacs commands are provided for moving over and operating on pages. See Pages.
Paragraphs are the medium-size unit of English text. There are special Emacs commands for moving over and operating on paragraphs. See Paragraphs.
We say that Emacs parses words or expressions in the text being edited. Really, all it knows how to do is find the other end of a word or expression. See Syntax.
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.
A prefix key is a key (q.v.) whose sole function is to introduce a set of multi-character keys. Control-x is an example of a prefix key; any two-character sequence starting with C-x is also a legitimate key. See Keystrokes.
A prompt is text printed to ask the user for input. Printing 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 which happens when you pause in the middle of typing a multi-character key is also a kind of prompting (see Echo Area).
Quitting means cancelling a partially typed command or a running command, using C-g. See Quitting.
Quoting means depriving a character of its usual special significance. In Emacs this is usually done with Control-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 Basic Editing.
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, such as Dired buffers. Visiting a file that is write-protected also makes a read-only buffer. See Buffers.
A recursive editing level is a state in which part of the execution of a command involves asking the user 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 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.
See ‘regular expression’.
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.
Registers are named slots in which text or buffer positions or rectangles can be saved for later use. See Registers.
A regular expression is a pattern that can match various text strings; for example, ‘l[0-9]+’ matches ‘l’ followed by one or more digits. See Regexps.
See ‘global substitution’.
A buffer’s restriction is the amount of text, at the beginning or the end of the buffer, that is temporarily invisible and inaccessible. Giving a buffer a nonzero amount of restriction is called narrowing (q.v.). See Narrowing.
RET is the character than 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.
Saving a buffer means copying its text into the file that was visited (q.v.) in that buffer. To actually change a file you have edited in Emacs, you have to save it. See Saving.
Scrolling means shifting the text in the Emacs window to make a different part of the buffer visible. See Scrolling.
Searching means moving point to the next occurrence of a specified string. See Search.
Selecting a buffer means making it the current (q.v.) buffer. See Selecting.
Self-documentation is the feature of Emacs which can tell you what any command does, or can 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.
Emacs has commands for moving by or killing by sentences. See Sentences.
An sexp (short for ‘s-expression,’ itself short for ‘symbolic expression’) is the basic syntactic unit of Lisp in its textual form: either a list, or Lisp atom. Many Emacs commands operate on sexps. The term ‘sexp’ is generalized to languages other than Lisp to mean a syntactically recognizable expression. See Sexps.
Simultaneous editing means two users modifying the same file at once. If simultaneous editing is not detected, you may lose your work. Emacs detects all cases of simultaneous editing and warns the user to investigate them. See Simultaneous Editing.
A string is a kind of Lisp data object which 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. Write a ‘"’ that is part of the string as ‘\"’ and a ‘\’ that is part of the string as ‘\\’. You can include all other characters, including newline, just by writing them inside the string. You can also include escape sequences as in C, such as ‘\n’ for newline or ‘\241’ using an octal character code.
See ‘global substitution’.
The syntax table tells Emacs which characters are part of a word, which characters balance each other like parentheses, etc. See Syntax.
A tag table is a file that serves as an index to the function definitions in one or more other files. See Tags.
A termscript file contains a record of all characters Emacs sent to the terminal. It is used for tracking down bugs in Emacs redisplay. Emacs does not make a termscript file unless explicitly instructed to do so. See Bugs.
Text has two meanings (see Text):
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.
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, sexps (q.v.), or lines (see Transpose).
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 also ‘continuation line’. See Basic Editing.
Undoing means making your previous editing go in reverse, bringing back the text that existed earlier in the editing session. See Undo.
A variable is Lisp object that can store an arbitrary value. Emacs uses some variables for internal purposes, and has others (known as ‘options’ (q.v.)) you can set 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 of this manual. See Variables, for information on variables.
Visiting a file means loading its contents into a buffer (q.v.) where they can be edited. See Visiting.
Whitespace is any run of consecutive formatting characters (spaces, tabs, newlines, and backspaces).
Widening is removing any restriction (q.v.) on the current buffer; it is the opposite of narrowing (q.v.). See Narrowing.
Emacs divides the frame into one or more windows, each of which can display the contents of one buffer (q.v.) at any time. See Frame, for basic information on how Emacs uses the frame. See Windows, for commands to control the use of windows. Note that if you are running Emacs under X, terminology can be confusing: Each Emacs frame occupies a separate X window and can, in turn, be divided into different subwindows.
Synonymous with ‘abbrev’.
Word search is searching for a sequence of words, considering the punctuation between them as insignificant. See Word Search.
Yanking means reinserting text previously killed. It can be used to undo a mistaken kill, or for copying or moving text. Some other systems call this “pasting”. See Yanking.