This is Info file ../../info/xemacs.info, produced by Makeinfo version 1.68 from the input file xemacs.texi. This file documents the XEmacs editor. Copyright (C) 1985, 1986, 1988 Richard M. Stallman. Copyright (C) 1991, 1992, 1993, 1994 Lucid, Inc. Copyright (C) 1993, 1994 Sun Microsystems, Inc. Copyright (C) 1995 Amdahl Corporation. Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided also that the sections entitled "The GNU Manifesto", "Distribution" and "GNU General Public License" are included exactly as in the original, and provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that the sections entitled "The GNU Manifesto", "Distribution" and "GNU General Public License" may be included in a translation approved by the author instead of in the original English.  File: xemacs.info, Node: Bugs, Prev: Lossage, Up: Top Reporting Bugs ============== Sometimes you will encounter a bug in Emacs. Although we cannot promise we can or will fix the bug, and we might not even agree that it is a bug, we want to hear about bugs you encounter in case we do want to fix them. To make it possible for us to fix a bug, you must report it. In order to do so effectively, you must know when and how to do it. When Is There a Bug ------------------- If Emacs executes an illegal instruction, or dies with an operating system error message that indicates a problem in the program (as opposed to something like "disk full"), then it is certainly a bug. If Emacs updates the display in a way that does not correspond to what is in the buffer, then it is certainly a bug. If a command seems to do the wrong thing but the problem corrects itself if you type `C-l', it is a case of incorrect display updating. Taking forever to complete a command can be a bug, but you must make certain that it was really Emacs's fault. Some commands simply take a long time. Type `C-g' and then `C-h l' to see whether the input Emacs received was what you intended to type; if the input was such that you KNOW it should have been processed quickly, report a bug. If you don't know whether the command should take a long time, find out by looking in the manual or by asking for assistance. If a command you are familiar with causes an Emacs error message in a case where its usual definition ought to be reasonable, it is probably a bug. If a command does the wrong thing, that is a bug. But be sure you know for certain what it ought to have done. If you aren't familiar with the command, or don't know for certain how the command is supposed to work, then it might actually be working right. Rather than jumping to conclusions, show the problem to someone who knows for certain. Finally, a command's intended definition may not be best for editing with. This is a very important sort of problem, but it is also a matter of judgment. Also, it is easy to come to such a conclusion out of ignorance of some of the existing features. It is probably best not to complain about such a problem until you have checked the documentation in the usual ways, feel confident that you understand it, and know for certain that what you want is not available. If you are not sure what the command is supposed to do after a careful reading of the manual, check the index and glossary for any terms that may be unclear. If you still do not understand, this indicates a bug in the manual. The manual's job is to make everything clear. It is just as important to report documentation bugs as program bugs. If the online documentation string of a function or variable disagrees with the manual, one of them must be wrong, so report the bug. How to Report a Bug ------------------- When you decide that there is a bug, it is important to report it and to report it in a way which is useful. What is most useful is an exact description of what commands you type, starting with the shell command to run Emacs, until the problem happens. Always include the version number of Emacs that you are using; type `M-x emacs-version' to print this. The most important principle in reporting a bug is to report FACTS, not hypotheses or categorizations. It is always easier to report the facts, but people seem to prefer to strain to posit explanations and report them instead. If the explanations are based on guesses about how Emacs is implemented, they will be useless; we will have to try to figure out what the facts must have been to lead to such speculations. Sometimes this is impossible. But in any case, it is unnecessary work for us. For example, suppose that you type `C-x C-f /glorp/baz.ugh ', visiting a file which (you know) happens to be rather large, and Emacs prints out `I feel pretty today'. The best way to report the bug is with a sentence like the preceding one, because it gives all the facts and nothing but the facts. Do not assume that the problem is due to the size of the file and say, "When I visit a large file, Emacs prints out `I feel pretty today'." This is what we mean by "guessing explanations". The problem is just as likely to be due to the fact that there is a `z' in the file name. If this is so, then when we got your report, we would try out the problem with some "large file", probably with no `z' in its name, and not find anything wrong. There is no way in the world that we could guess that we should try visiting a file with a `z' in its name. Alternatively, the problem might be due to the fact that the file starts with exactly 25 spaces. For this reason, you should make sure that you inform us of the exact contents of any file that is needed to reproduce the bug. What if the problem only occurs when you have typed the `C-x a l' command previously? This is why we ask you to give the exact sequence of characters you typed since starting to use Emacs. You should not even say "visit a file" instead of `C-x C-f' unless you know that it makes no difference which visiting command is used. Similarly, rather than saying "if I have three characters on the line," say "after I type ` A B C C-p'," if that is the way you entered the text. If you are not in Fundamental mode when the problem occurs, you should say what mode you are in. If the manifestation of the bug is an Emacs error message, it is important to report not just the text of the error message but a backtrace showing how the Lisp program in Emacs arrived at the error. To make the backtrace, you must execute the Lisp expression `(setq debug-on-error t)' before the error happens (that is to say, you must execute that expression and then make the bug happen). This causes the Lisp debugger to run (*note Lisp Debug::.). The debugger's backtrace can be copied as text into the bug report. This use of the debugger is possible only if you know how to make the bug happen again. Do note the error message the first time the bug happens, so if you can't make it happen again, you can report at least that. Check whether any programs you have loaded into the Lisp world, including your `.emacs' file, set any variables that may affect the functioning of Emacs. Also, see whether the problem happens in a freshly started Emacs without loading your `.emacs' file (start Emacs with the `-q' switch to prevent loading the init file). If the problem does NOT occur then, it is essential that we know the contents of any programs that you must load into the Lisp world in order to cause the problem to occur. If the problem does depend on an init file or other Lisp programs that are not part of the standard Emacs system, then you should make sure it is not a bug in those programs by complaining to their maintainers first. After they verify that they are using Emacs in a way that is supposed to work, they should report the bug. If you can tell us a way to cause the problem without visiting any files, please do so. This makes it much easier to debug. If you do need files, make sure you arrange for us to see their exact contents. For example, it can often matter whether there are spaces at the ends of lines, or a newline after the last line in the buffer (nothing ought to care whether the last line is terminated, but tell that to the bugs). The easy way to record the input to Emacs precisely is to write a dribble file; execute the Lisp expression: (open-dribble-file "~/dribble") using `Meta-' or from the `*scratch*' buffer just after starting Emacs. From then on, all Emacs input will be written in the specified dribble file until the Emacs process is killed. For possible display bugs, it is important to report the terminal type (the value of environment variable `TERM'), the complete termcap entry for the terminal from `/etc/termcap' (since that file is not identical on all machines), and the output that Emacs actually sent to the terminal. The way to collect this output is to execute the Lisp expression: (open-termscript "~/termscript") using `Meta-' or from the `*scratch*' buffer just after starting Emacs. From then on, all output from Emacs to the terminal will be written in the specified termscript file as well, until the Emacs process is killed. If the problem happens when Emacs starts up, put this expression into your `.emacs' file so that the termscript file will be open when Emacs displays the screen for the first time. Be warned: it is often difficult, and sometimes impossible, to fix a terminal-dependent bug without access to a terminal of the type that stimulates the bug. The newsgroup `comp.emacs.xemacs' may be used for bug reports, other discussions and requests for assistance. If you don't have access to this newgroup, you can subscribe to the mailing list version: the newsgroup is bidirectionally gatewayed into the mailing list `xemacs@xemacs.org'. To be added or removed from this mailing list, send mail to `xemacs-request@xemacs.org'. Do not send requests for addition to the mailing list itself. The mailing lists and newsgroups are archived on our anonymous FTP server, `ftp.xemacs.org', and at various other archive sites around the net. You should also check the `FAQ' in `/pub/xemacs' on our anonymous FTP server. It provides some introductory information and help for initial configuration problems.  File: xemacs.info, Node: Glossary, Next: Manifesto, Prev: Intro, Up: Top Glossary ******** Abbrev 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. *Note Abbrevs::. Aborting Aborting means getting out of a recursive edit (q.v.). You can use the commands `C-]' and `M-x top-level' for this. *Note Quitting::. Auto Fill mode Auto Fill mode is a minor mode in which text you insert is automatically broken into lines of fixed width. *Note Filling::. Auto Saving 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. *Note Auto Save::. Backup File 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. *Note Backup::. Balance Parentheses Emacs can balance parentheses manually or automatically. Manual balancing is done by the commands to move over balanced expressions (*note Lists::.). Automatic balancing is done by blinking the parenthesis that matches one just inserted (*note Matching Parens: Matching.). Bind To bind a key is to change its binding (q.v.). *Note Rebinding::. Binding 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. *Note Binding: Commands. Customization often involves rebinding a character to a different command function. The bindings of all keys are recorded in the keymaps (q.v.). *Note Keymaps::. Blank Lines Blank lines are lines that contain only whitespace. Emacs has several commands for operating on the blank lines in a buffer. 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. *Note Buffers::. Buffer Selection History 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. *Note Buffers::. C- `C' in the name of a character is an abbreviation for Control. *Note C-: Keystrokes. C-M- `C-M-' in the name of a character is an abbreviation for Control-Meta. *Note C-M-: Keystrokes. Case Conversion Case conversion means changing text from upper case to lower case or vice versa. *Note Case::, for the commands for case conversion. Characters 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. *Note Keystrokes::. 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 (q.v.), Emacs looks up its binding (q.v.) in the relevant keymaps (q.v.) to find the command to run. *Note Commands::. Command Name A command name is the name of a Lisp symbol which is a command (*note Commands::.). You can invoke any command by its name using `M-x' (*note M-x::.). Comments 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. *Note Comments::. Compilation Compilation is the process of creating an executable program from source code. Emacs has commands for compiling files of Emacs Lisp code (*note Lisp Libraries::.) and programs in C and other languages (*note Compilation::.). Complete Key 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. *Note Keystrokes::. Completion 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 , , or . *Note Completion::. Continuation Line 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. *Note Continuation: Basic. Control-Character 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 key and typing some other character; some have special keys on the keyboard. , , , , and are all control characters. *Note Keystrokes::. Copyleft 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. 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. *Note Buffers::. Current Line The line point is on (*note Point::.). Current Paragraph The paragraph that point is in. If point is between paragraphs, the current paragraph is the one that follows point. *Note Paragraphs::. Current Defun The defun (q.v.) that point is in. If point is between defuns, the current defun is the one that follows point. *Note 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'. *Note Cursor: Basic. Customization Customization is making minor changes in the way Emacs works. It is often done by setting variables (*note Variables::.) or by rebinding keys (*note Keymaps::.). Default Argument 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 . *Note Minibuffer::. 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. *Note Default Directory: Minibuffer File. Defun 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'. *Note Defuns::. The character runs the command that deletes one character of text. *Note DEL: Basic. Deletion 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.). *Note Deletion: Killing. Deletion of Files Deleting a file means removing it from the file system. *Note Misc File Ops::. Deletion of Messages 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. Deletion of Frames When working under the multi-frame X-based version of XEmacs, you can delete individual frames using the Close menu item from the File menu. Deletion of Windows 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. *Note Windows::. Directory Files in the Unix file system are grouped into file directories. *Note Directories: ListDir. 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. *Note Dired::. Disabled Command A disabled command is one that you may not run without special confirmation. Commands are usually disabled because they are confusing for beginning users. *Note Disabling::. Dribble File 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. *Note Bugs::. Echo Area 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). *Note Echo Area::. Echoing 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. 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 printing an error message (q.v.). Type-ahead is discarded. Then Emacs is ready to read another editing command. Error Messages 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. is a character used as a prefix for typing Meta characters on keyboards lacking a key. Unlike the key (which, like the key, is held down while another character is typed), the key is pressed and released, and applies to the next character typed. Fill Prefix 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. *Note Filling::. Filling Filling text means moving text from line to line so that all the lines are approximately the same length. *Note Filling::. Frame 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. Global 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. 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. *Note Abbrevs::. Global Keymap 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.*Note Keymaps::. Global Substitution Global substitution means replacing each occurrence of one string by another string through a large amount of text. *Note 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. *Note Variables::. 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.) character are graphic characters. These include letters, digits, punctuation, and spaces; they do not include or . In Emacs, typing a graphic character inserts that character (in ordinary editing modes). *Note Basic Editing: Basic. Grinding Grinding means adjusting the indentation in a program to fit the nesting structure. *Note Grinding: Indentation. Hardcopy Hardcopy means printed output. Emacs has commands for making printed listings of text in Emacs buffers. *Note Hardcopy::. You can type at any time to ask what options you have, or to ask what any command does. is really `Control-h'. *Note Help::. Inbox 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 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. *Note Indentation::. Insertion Insertion means copying text into the buffer, either from the keyboard or from some other place in Emacs. Justification Justification means adding extra spaces to lines of text to make them come exactly to a specified width. *Note Justification: Filling. Keyboard Macros Keyboard macros are a way of defining new Emacs commands from sequences of existing ones, with no need to write a Lisp program. *Note Keyboard Macros::. Key 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.). *Note Keystrokes::. Keymap 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'. *Note Keymaps::. Kill Ring 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.). *Note 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 to erase text do killing, as opposed to deletion (q.v.). *Note Killing::. Killing Jobs 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. *Note Exiting::. 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. *Note Lists::. 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. Local 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. *Note 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 keys. *Note Keymaps::. Local Variable A local value of a variable (q.v.) applies to only one buffer. *Note Locals::. M- `M-' in the name of a character is an abbreviation for , one of the modifier keys that can accompany any character. *Note Keystrokes::. M-C- `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 key, you type a Control-Meta character by typing and then typing the corresponding Control character. *Note C-M-: Keystrokes. M-x `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. *Note M-x::. 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. *Note Sending Mail::. Major Mode 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. *Note Major Modes::. 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 the whole region, that is, all the text from point to the mark. *Note Mark::. Mark Ring The mark ring is used to hold several recent previous locations of the mark, just in case you want to move back to them. *Note Mark Ring::. Message See `mail'. Meta 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 key held down. Such characters are given names that start with `Meta-'. For example, `Meta-<' is typed by holding down and at the same time typing `<' (which itself is done, on most terminals, by holding down and typing `,'). *Note Meta: Keystrokes. Meta Character A Meta character is one whose character code includes the Meta bit. Minibuffer The minibuffer is the window that Emacs displays inside the echo area (q.v.) when it prompts you for arguments to commands. *Note Minibuffer::. Minor Mode 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. *Note Minor Modes::. Mode Line 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. *Note 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). *Note Saving::. Moving Text 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.). *Note Killing::. 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. *Note Registers::. Narrowing 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. *Note Narrowing::. Newline characters in the buffer terminate lines of text and are called newlines. *Note Newline: Keystrokes. 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. *Note Arguments::. Option An option is a variable (q.v.) that allows you to customize Emacs by giving it a new value. *Note Variables::. 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 the right. *Note Minor Modes::. Page 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. *Note Pages::. Paragraphs Paragraphs are the medium-size unit of English text. There are special Emacs commands for moving over and operating on paragraphs. *Note Paragraphs::. Parsing 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. *Note Syntax::. 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. *Note Point: Basic. Prefix Key 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. *Note Keystrokes::. Prompt 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 (*note Minibuffer::.); the echoing which happens when you pause in the middle of typing a multi-character key is also a kind of prompting (*note Echo Area::.). Quitting Quitting means cancelling a partially typed command or a running command, using `C-g'. *Note Quitting::. Quoting 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 , for example), and quoting it makes it insert itself as if it were not special. Not all contexts allow quoting. *Note Quoting: Basic. Read-only Buffer 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 asDired buffers. Visiting a file that is write-protected also makes a read-only buffer. *Note Buffers::. Recursive Editing Level 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 `]'). *Note 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. *Note Redisplay: Frame. Regexp See `regular expression'. Region The region is the text between point (q.v.) and the mark (q.v.). Many commands operate on the text of the region. *Note Region: Mark. Registers Registers are named slots in which text or buffer positions or rectangles can be saved for later use. *Note Registers::. Regular Expression 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. *Note Regexps::. Replacement See `global substitution'. Restriction 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.). *Note Narrowing::. 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.). *Note Return: Keystrokes. Saving 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. *Note Saving::. Scrolling Scrolling means shifting the text in the Emacs window to make a different part ot the buffer visible. *Note Scrolling: Display. Searching Searching means moving point to the next occurrence of a specified string. *Note Search::. Selecting Selecting a buffer means making it the current (q.v.) buffer. *Note Selecting: Buffers. Self-documentation 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'. *Note Help::. Sentences Emacs has commands for moving by or killing by sentences. *Note Sentences::. Sexp 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. *Note Sexps: Lists. Simultaneous Editing 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. *Note Simultaneous Editing: Interlocking. String 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. String Substitution See `global substitution'. Syntax Table The syntax table tells Emacs which characters are part of a word, which characters balance each other like parentheses, etc. *Note Syntax::. Tag Table A tag table is a file that serves as an index to the function definitions in one or more other files. *Note Tags::. Termscript File 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. *Note Bugs::. Text Text has two meanings (*note Text::.): * Data consisting of a sequence of characters, as opposed to binary numbers, images, graphics commands, executable programs, and the like. The contents of an Emacs buffer are always text in this sense. * Data consisting of written human language, as opposed to programs, or something that follows the stylistic conventions of human language. 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.). *Note Quitting::. 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, sexps (q.v.), or lines (*note Transpose::.). 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 also `continuation line'. *Note Truncation: Basic. Undoing Undoing means making your previous editing go in reverse, bringing back the text that existed earlier in the editing session. *Note Undo::. Variable 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. *Note Variables::, for information on variables. Visiting Visiting a file means loading its contents into a buffer (q.v.) where they can be edited. *Note Visiting::. Whitespace Whitespace is any run of consecutive formatting characters (spaces, tabs, newlines, and backspaces). Widening Widening is removing any restriction (q.v.) on the current buffer; it is the opposite of narrowing (q.v.). *Note Narrowing::. Window Emacs divides the frame into one or more windows, each of which can display the contents of one buffer (q.v.) at any time. *Note Frame::, for basic information on how Emacs uses the frame. *Note 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. Word Abbrev Synonymous with `abbrev'. Word Search Word search is searching for a sequence of words, considering the punctuation between them as insignificant. *Note Word Search::. Yanking 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". *Note Yanking::.