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GNU Info File | 1992-02-21 | 49KB | 831 lines

This is Info file ../info/emacs, produced by Makeinfo-1.43 from the input file emacs.tex. This file documents the GNU Emacs editor. Copyright (C) 1985, 1986, 1988 Richard M. Stallman. 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: emacs, Node: Top, Next: Distrib, Up: (DIR) The Emacs Editor **************** Emacs is the extensible, customizable, self-documenting real-time display editor. This Info file describes how to edit with Emacs and some of how to customize it, but not how to extend it. * Menu: * Distrib:: How to get the latest Emacs distribution. * License:: The GNU General Public License gives you permission to redistribute GNU Emacs on certain terms; and also explains that there is no warranty. * Intro:: An introduction to Emacs concepts. * Glossary:: The glossary. * Manifesto:: What's GNU? Gnu's Not Unix! Indexes, nodes containing large menus * Key Index:: An item for each standard Emacs key sequence. * Command Index:: An item for each command name. * Variable Index:: An item for each documented variable. * Concept Index:: An item for each concept. Important General Concepts * Screen:: How to interpret what you see on the screen. * Characters:: Emacs's character sets for file contents and for keyboard. * Keys:: Key sequences: what you type to request one editing action. * Commands:: Commands: named functions run by key sequences to do editing. * Entering Emacs:: Starting Emacs from the shell. * Command Switches:: Hairy startup options. * Exiting:: Stopping or killing Emacs. * Basic:: The most basic editing commands. * Undo:: Undoing recently made changes in the text. * Minibuffer:: Entering arguments that are prompted for. * M-x:: Invoking commands by their names. * Help:: Commands for asking Emacs about its commands. Important Text-Changing Commands * Mark:: The mark: how to delimit a "region" of text. * Killing:: Killing text. * Yanking:: Recovering killed text. Moving text. * Accumulating Text:: Other ways of copying text. * Rectangles:: Operating on the text inside a rectangle on the screen. * Registers:: Saving a text string or a location in the buffer. * Display:: Controlling what text is displayed. * Search:: Finding or replacing occurrences of a string. * Fixit:: Commands especially useful for fixing typos. Larger Units of Text * Files:: All about handling files. * Buffers:: Multiple buffers; editing several files at once. * Windows:: Viewing two pieces of text at once. Advanced Features * Major Modes:: Text mode vs. Lisp mode vs. C mode ... * Indentation:: Editing the white space at the beginnings of lines. * Text:: Commands and modes for editing English. * Programs:: Commands and modes for editing programs. * Running:: Compiling, running and debugging programs. * Abbrevs:: How to define text abbreviations to reduce the number of characters you must type. * Picture:: Editing pictures made up of characters using the quarter-plane screen model. * Sending Mail::Sending mail in Emacs. * Rmail:: Reading mail in Emacs. * Recursive Edit:: A command can allow you to do editing "within the command". This is called a `recursive editing level'. * Narrowing:: Restricting display and editing to a portion of the buffer. * Sorting:: Sorting lines, paragraphs or pages within Emacs. * Shell:: Executing shell commands from Emacs. * Hardcopy:: Printing buffers or regions. * Dissociated Press:: Dissociating text for fun. * Amusements:: Various games and hacks. * Emulation:: Emulating some other editors with Emacs. * Customization:: Modifying the behavior of Emacs. Recovery from Problems. * Quitting:: Quitting and aborting. * Lossage:: What to do if Emacs is hung or malfunctioning. * Bugs:: How and when to report a bug. Here are some other nodes which are really inferiors of the ones already listed, mentioned here so you can get to them in one step: Subnodes of Screen * Point:: The place in the text where editing commands operate. * Echo Area:: Short messages appear at the bottom of the screen. * Mode Line:: Interpreting the mode line. Subnodes of Basic * Blank Lines:: Commands to make or delete blank lines. * Continuation Lines:: Lines too wide for the screen. * Position Info:: What page, line, row, or column is point on? * Arguments:: Giving numeric arguments to commands. Subnodes of Minibuffer * Minibuffer File:: Entering file names with the minibuffer. * Minibuffer Edit:: How to edit in the minibuffer. * Completion:: An abbreviation facility for minibuffer input. * Repetition:: Re-executing previous commands that used the minibuffer. Subnodes of Mark * Setting Mark:: Commands to set the mark. * Using Region:: Summary of ways to operate on contents of the region. * Marking Objects:: Commands to put region around textual units. * Mark Ring:: Previous mark positions saved so you can go back there. Subnodes of Yanking * Kill Ring:: Where killed text is stored. Basic yanking. * Appending Kills:: Several kills in a row all yank together. * Earlier Kills:: Yanking something killed some time ago. Subnodes of Registers * RegPos:: Saving positions in registers. * RegText:: Saving text in registers. * RegRect:: Saving rectangles in registers. Subnodes of Display * Scrolling:: Moving text up and down in a window. * Horizontal Scrolling:: Moving text left and right in a window. * Selective Display:: Hiding lines with lots of indentation. * Display Vars:: Information on variables for customizing display. Subnodes of Search * Incremental Search:: Search happens as you type the string. * Nonincremental Search:: Specify entire string and then search. * Word Search:: Search for sequence of words. * Regexp Search:: Search for match for a regexp. * Regexps:: Syntax of regular expressions. * Search Case:: To ignore case while searching, or not. * Replace:: Search, and replace some or all matches. * Unconditional Replace:: Everything about replacement except for querying. * Query Replace:: How to use querying. * Other Repeating Search:: Operating on all matches for some regexp. Subnodes of Fixit * Kill Errors:: Commands to kill a batch of recently entered text. * Transpose:: Exchanging two characters, words, lines, lists... * Fixing Case:: Correcting case of last word entered. * Spelling:: Apply spelling checker to a word, or a whole file. Subnodes of Files * File Names:: How to type and edit file name arguments. * Visiting:: Visiting a file prepares Emacs to edit the file. * Saving:: Saving makes your changes permanent. * Backup:: How Emacs saves the old version of your file. * Interlocking::How Emacs protects against simultaneous editing of one file by two users. * Reverting:: Reverting cancels all the changes not saved. * Auto Save:: Auto Save periodically protects against loss of data. * ListDir:: Listing the contents of a file directory. * Dired:: "Editing" a directory to delete, rename, etc. the files in it. * Misc File Ops:: Other things you can do on files. Subnodes of Buffers * Select Buffer:: Creating a new buffer or reselecting an old one. * List Buffers:: Getting a list of buffers that exist. * Misc Buffer:: Renaming; changing read-only status. * Kill Buffer:: Killing buffers you no longer need. * Several Buffers:: How to go through the list of all buffers and operate variously on several of them. Subnodes of Windows * Basic Window:: Introduction to Emacs windows. * Split Window:: New windows are made by splitting existing windows. * Other Window:: Moving to another window or doing something to it. * Pop Up Window:: Finding a file or buffer in another window. * Change Window:: Deleting windows and changing their sizes. Subnodes of Indentation * Indentation Commands:: Various commands and techniques for indentation. * Tab Stops:: You can set arbitrary "tab stops" and then indent to the next tab stop when you want to. * Just Spaces:: You can request indentation using just spaces. Subnodes of Text * Text Mode:: The major mode for editing text files. * Nroff Mode:: The major mode for editing input to the formatter nroff. * TeX Mode:: The major mode for editing input to the formatter TeX. * Outline Mode::The major mode for editing outlines. * Words:: Moving over and killing words. * Sentences:: Moving over and killing sentences. * Paragraphs:: Moving over paragraphs. * Pages:: Moving over pages. * Filling:: Filling or justifying text * Case:: Changing the case of text Subnodes of Programs * Program Modes:: Major modes for editing programs. * Lists:: Expressions with balanced parentheses. There are editing commands to operate on them. * Defuns:: Each program is made up of separate functions. There are editing commands to operate on them. * Grinding:: Adjusting indentation to show the nesting. * Matching:: Insertion of a close-delimiter flashes matching open. * Comments:: Inserting, illing and aligning comments. * Balanced Editing:: Inserting two matching parentheses at once, etc. * Lisp Completion:: Completion on symbol names in Lisp code. * Documentation:: Getting documentation of functions you plan to call. * Change Log:: Maintaining a change history for your program. * Tags:: Go direct to any function in your program in one command. Tags remembers which file it is in. * Fortran:: Fortran mode and its special features. Subnodes of Running * Compilation:: Compiling programs in languages other than Lisp (C, Pascal, etc.) * Lisp Modes:: Various modes for editing Lisp programs, with different facilities for running the Lisp programs. * Lisp Libraries:: Creating Lisp programs to run in Emacs. * Lisp Interaction:: Executing Lisp in an Emacs buffer. * Lisp Eval:: Executing a single Lisp expression in Emacs. * Lisp Debug:: Debugging Lisp programs running in Emacs. * External Lisp:: Communicating through Emacs with a separate Lisp. Subnodes of Abbrevs * Defining Abbrevs:: Defining an abbrev, so it will expand when typed. * Expanding Abbrevs:: Controlling expansion: prefixes, canceling expansion. * Editing Abbrevs:: Viewing or editing the entire list of defined abbrevs. * Saving Abbrevs:: Saving the entire list of abbrevs for another session. * Dynamic Abbrevs:: Abbreviations for words already in the buffer. Subnodes of Picture * Basic Picture:: Basic concepts and simple commands of Picture Mode. * Insert in Picture:: Controlling direction of cursor motion after "self-inserting" characters. * Tabs in Picture:: Various features for tab stops and indentation. * Rectangles in Picture:: Clearing and superimposing rectangles. Subnodes of Sending Mail * Mail Format:: Format of the mail being composed. * Mail Headers:: Details of allowed mail header fields. * Mail Mode:: Special commands for editing mail being composed. Subnodes of Rmail * Rmail Scrolling:: Scrolling through a message. * Rmail Motion:: Moving to another message. * Rmail Deletion:: Deleting and expunging messages. * Rmail Inbox:: How mail gets into the Rmail file. * Rmail Files:: Using multiple Rmail files. * Rmail Output:: Copying message out to files. * Rmail Labels:: Classifying messages by labeling them. * Rmail Summary:: Summaries show brief info on many messages. * Rmail Reply:: Sending replies to messages you are viewing. * Rmail Editing:: Editing message text and headers in Rmail. * Rmail Digest:: Extracting the messages from a digest message. Subnodes of Shell * Single Shell:: Commands to run one shell command and return. * Interactive Shell:: Permanent shell taking input via Emacs. * Shell Mode:: Special Emacs commands used with permanent shell. Subnodes of Customization * Minor Modes:: Each minor mode is one feature you can turn on independently of any others. * Variables:: Many Emacs commands examine Emacs variables to decide what to do; by setting variables, you can control their functioning. * Examining:: Examining or setting one variable's value. * Edit Options:: Examining or editing list of all variables' values. * Locals:: Per-buffer values of variables. * File Variables:: How files can specify variable values. * Keyboard Macros:: A keyboard macro records a sequence of keystrokes to be replayed with a single command. * Key Bindings:: The keymaps say what command each key runs. By changing them, you can "redefine keys". * Keymaps:: Definition of the keymap data structure. * Rebinding:: How to redefine one key's meaning conveniently. * Disabling:: Disabling a command means confirmation is required before it can be executed. This is done to protect beginners from surprises. * Syntax:: The syntax table controls how words and expressions are parsed. * Init File:: How to write common customizations in the `.emacs' file. Subnodes of Lossage (and recovery) * Stuck Recursive:: `[...]' in mode line around the parentheses. * Screen Garbled:: Garbage on the screen. * Text Garbled:: Garbage in the text. * Unasked-for Search::Spontaneous entry to incremental search. * Emergency Escape:: Emergency escape-- What to do if Emacs stops responding. * Total Frustration:: When you are at your wits' end. File: emacs, Node: Distrib, Next: License, Prev: Top, Up: Top Distribution ************ GNU Emacs is "free"; this means that everyone is free to use it and free to redistribute it on a free basis. GNU Emacs is not in the public domain; it is copyrighted and there are restrictions on its distribution, but these restrictions are designed to permit everything that a good cooperating citizen would want to do. What is not allowed is to try to prevent others from further sharing any version of GNU Emacs that they might get from you. The precise conditions are found in the GNU General Public License that comes with Emacs and also appears following this section. The easiest way to get a copy of GNU Emacs is from someone else who has it. You need not ask for permission to do so, or tell any one else; just copy it. If you have access to the Internet, you can get the latest distribution version of GNU Emacs from host `prep.ai.mit.edu' using anonymous login. See the file `/u2/emacs/GETTING.GNU.SOFTWARE' on that host to find out about your options for copying and which files to use. You may also receive GNU Emacs when you buy a computer. Computer manufacturers are free to distribute copies on the same terms that apply to everyone else. These terms require them to give you the full sources, including whatever changes they may have made, and to permit you to redistribute the GNU Emacs received from them under the usual terms of the General Public License. In other words, the program must be free for you when you get it, not just free for the manufacturer. If you cannot get a copy in any of those ways, you can order one from the Free Software Foundation. Though Emacs itself is free, our distribution service is not. An order form is included at the end of manuals printed by the Foundation. It is also included in the file `etc/DISTRIB' in the Emacs distribution. For further information, write to Free Software Foundation 675 Mass Ave Cambridge, MA 02139 USA The income from distribution fees goes to support the foundation's purpose: the development of more free software to distribute just like GNU Emacs. If you find GNU Emacs useful, please send a donation to the Free Software Foundation. This will help support development of the rest of the GNU system, and other useful software beyond that. Your donation is tax deductible. File: emacs, Node: License, Next: Intro, Prev: Distrib, Up: Top GNU GENERAL PUBLIC LICENSE ************************** Version 1, February 1989 Copyright (C) 1989 Free Software Foundation, Inc. 675 Mass Ave, Cambridge, MA 02139, USA Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed. Preamble ======== The license agreements of most software companies try to keep users at the mercy of those companies. By contrast, our General Public License is intended to guarantee your freedom to share and change free software--to make sure the software is free for all its users. The General Public License applies to the Free Software Foundation's software and to any other program whose authors commit to using it. You can use it for your programs, too. When we speak of free software, we are referring to freedom, not price. Specifically, the General Public License is designed to make sure that you have the freedom to give away or sell copies of free software, that you receive source code or can get it if you want it, that you can change the software or use pieces of it in new free programs; and that you know you can do these things. To protect your rights, we need to make restrictions that forbid anyone to deny you these rights or to ask you to surrender the rights. These restrictions translate to certain responsibilities for you if you distribute copies of the software, or if you modify it. For example, if you distribute copies of a such a program, whether gratis or for a fee, you must give the recipients all the rights that you have. You must make sure that they, too, receive or can get the source code. And you must tell them their rights. We protect your rights with two steps: (1) copyright the software, and (2) offer you this license which gives you legal permission to copy, distribute and/or modify the software. Also, for each author's protection and ours, we want to make certain that everyone understands that there is no warranty for this free software. If the software is modified by someone else and passed on, we want its recipients to know that what they have is not the original, so that any problems introduced by others will not reflect on the original authors' reputations. The precise terms and conditions for copying, distribution and modification follow. TERMS AND CONDITIONS 1. This License Agreement applies to any program or other work which contains a notice placed by the copyright holder saying it may be distributed under the terms of this General Public License. The "Program", below, refers to any such program or work, and a "work based on the Program" means either the Program or any work containing the Program or a portion of it, either verbatim or with modifications. Each licensee is addressed as "you". 2. You may copy and distribute verbatim copies of the Program's source code as you receive it, in any medium, provided that you conspicuously and appropriately publish on each copy an appropriate copyright notice and disclaimer of warranty; keep intact all the notices that refer to this General Public License and to the absence of any warranty; and give any other recipients of the Program a copy of this General Public License along with the Program. You may charge a fee for the physical act of transferring a copy. 3. You may modify your copy or copies of the Program or any portion of it, and copy and distribute such modifications under the terms of Paragraph 1 above, provided that you also do the following: * cause the modified files to carry prominent notices stating that you changed the files and the date of any change; and * cause the whole of any work that you distribute or publish, that in whole or in part contains the Program or any part thereof, either with or without modifications, to be licensed at no charge to all third parties under the terms of this General Public License (except that you may choose to grant warranty protection to some or all third parties, at your option). * If the modified program normally reads commands interactively when run, you must cause it, when started running for such interactive use in the simplest and most usual way, to print or display an announcement including an appropriate copyright notice and a notice that there is no warranty (or else, saying that you provide a warranty) and that users may redistribute the program under these conditions, and telling the user how to view a copy of this General Public License. * You may charge a fee for the physical act of transferring a copy, and you may at your option offer warranty protection in exchange for a fee. Mere aggregation of another independent work with the Program (or its derivative) on a volume of a storage or distribution medium does not bring the other work under the scope of these terms. 4. You may copy and distribute the Program (or a portion or derivative of it, under Paragraph 2) in object code or executable form under the terms of Paragraphs 1 and 2 above provided that you also do one of the following: * accompany it with the complete corresponding machine-readable source code, which must be distributed under the terms of Paragraphs 1 and 2 above; or, * accompany it with a written offer, valid for at least three years, to give any third party free (except for a nominal charge for the cost of distribution) a complete machine-readable copy of the corresponding source code, to be distributed under the terms of Paragraphs 1 and 2 above; or, * accompany it with the information you received as to where the corresponding source code may be obtained. (This alternative is allowed only for noncommercial distribution and only if you received the program in object code or executable form alone.) Source code for a work means the preferred form of the work for making modifications to it. For an executable file, complete source code means all the source code for all modules it contains; but, as a special exception, it need not include source code for modules which are standard libraries that accompany the operating system on which the executable file runs, or for standard header files or definitions files that accompany that operating system. 5. You may not copy, modify, sublicense, distribute or transfer the Program except as expressly provided under this General Public License. Any attempt otherwise to copy, modify, sublicense, distribute or transfer the Program is void, and will automatically terminate your rights to use the Program under this License. However, parties who have received copies, or rights to use copies, from you under this General Public License will not have their licenses terminated so long as such parties remain in full compliance. 6. By copying, distributing or modifying the Program (or any work based on the Program) you indicate your acceptance of this license to do so, and all its terms and conditions. 7. Each time you redistribute the Program (or any work based on the Program), the recipient automatically receives a license from the original licensor to copy, distribute or modify the Program subject to these terms and conditions. You may not impose any further restrictions on the recipients' exercise of the rights granted herein. 8. The Free Software Foundation may publish revised and/or new versions of the General Public License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. Each version is given a distinguishing version number. If the Program specifies a version number of the license which applies to it and "any later version", you have the option of following the terms and conditions either of that version or of any later version published by the Free Software Foundation. If the Program does not specify a version number of the license, you may choose any version ever published by the Free Software Foundation. 9. If you wish to incorporate parts of the Program into other free programs whose distribution conditions are different, write to the author to ask for permission. For software which is copyrighted by the Free Software Foundation, write to the Free Software Foundation; we sometimes make exceptions for this. Our decision will be guided by the two goals of preserving the free status of all derivatives of our free software and of promoting the sharing and reuse of software generally. NO WARRANTY 10. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION. 11. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. END OF TERMS AND CONDITIONS Appendix: How to Apply These Terms to Your New Programs ======================================================= If you develop a new program, and you want it to be of the greatest possible use to humanity, the best way to achieve this is to make it free software which everyone can redistribute and change under these terms. To do so, attach the following notices to the program. It is safest to attach them to the start of each source file to most effectively convey the exclusion of warranty; and each file should have at least the "copyright" line and a pointer to where the full notice is found. ONE LINE TO GIVE THE PROGRAM'S NAME AND A BRIEF IDEA OF WHAT IT DOES. Copyright (C) 19YY NAME OF AUTHOR This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 1, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. Also add information on how to contact you by electronic and paper mail. If the program is interactive, make it output a short notice like this when it starts in an interactive mode: Gnomovision version 69, Copyright (C) 19YY NAME OF AUTHOR Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type `show w'. This is free software, and you are welcome to redistribute it under certain conditions; type `show c' for details. The hypothetical commands `show w' and `show c' should show the appropriate parts of the General Public License. Of course, the commands you use may be called something other than `show w' and `show c'; they could even be mouse-clicks or menu items--whatever suits your program. You should also get your employer (if you work as a programmer) or your school, if any, to sign a "copyright disclaimer" for the program, if necessary. Here a sample; alter the names: Yoyodyne, Inc., hereby disclaims all copyright interest in the program `Gnomovision' (a program to direct compilers to make passes at assemblers) written by James Hacker. SIGNATURE OF TY COON, 1 April 1989 Ty Coon, President of Vice That's all there is to it! File: emacs, Node: Intro, Next: Glossary, Prev: License, Up: Top Introduction ************ You are reading about GNU Emacs, the GNU incarnation of the advanced, self-documenting, customizable, extensible real-time display editor Emacs. (The `G' in `GNU' is not silent.) We say that Emacs is a "display" editor because normally the text being edited is visible on the screen and is updated automatically as you type your commands. *Note Display: Screen. We call it a "real-time" editor because the display is updated very frequently, usually after each character or pair of characters you type. This minimizes the amount of information you must keep in your head as you edit. *Note Real-time: Basic. We call Emacs advanced because it provides facilities that go beyond simple insertion and deletion: filling of text; automatic indentation of programs; viewing two or more files at once; and dealing in terms of characters, words, lines, sentences, paragraphs, and pages, as well as expressions and comments in several different programming languages. It is much easier to type one command meaning "go to the end of the paragraph" than to find that spot with simple cursor keys. "Self-documenting" means that at any time you can type a special character, `Control-h', to find out what your options are. You can also use it to find out what any command does, or to find all the commands that pertain to a topic. *Note Help::. "Customizable" means that you can change the definitions of Emacs commands in little ways. For example, if you use a programming language in which comments start with `<**' and end with `**>', you can tell the Emacs comment manipulation commands to use those strings (*note Comments::.). Another sort of customization is rearrangement of the command set. For example, if you prefer the four basic cursor motion commands (up, down, left and right) on keys in a diamond pattern on the keyboard, you can have it. *Note Customization::. "Extensible" means that you can go beyond simple customization and write entirely new commands, programs in the Lisp language to be run by Emacs's own Lisp interpreter. Emacs is an "on-line extensible" system, which means that it is divided into many functions that call each other, any of which can be redefined in the middle of an editing session. Any part of Emacs can be replaced without making a separate copy of all of Emacs. Most of the editing commands of Emacs are written in Lisp already; the few exceptions could have been written in Lisp but are written in C for efficiency. Although only a programmer can write an extension, anybody can use it afterward. File: emacs, Node: Screen, Next: Characters, Prev: Concept Index, Up: Top The Organization of the Screen ****************************** Emacs divides the screen into several areas, each of which contains its own sorts of information. The biggest area, of course, is the one in which you usually see the text you are editing. When you are using Emacs, the screen is divided into a number of "windows". Initially there is one text window occupying all but the last line, plus the special "echo area" or "minibuffer window" in the last line. The text window can be subdivided horizontally or vertically into multiple text windows, each of which can be used for a different file (*note Windows::.). The window that the cursor is in is the "selected window", in which editing takes place. The other windows are just for reference unless you select one of them. Each text window's last line is a "mode line" which describes what is going on in that window. It is in inverse video if the terminal supports that, and contains text that starts like `-----Emacs: SOMETHING'. Its purpose is to indicate what buffer is being displayed above it in the window; what major and minor modes are in use; and whether the buffer's text has been changed. * Menu: * Point:: The place in the text where editing commands operate. * Echo Area:: Short messages appear at the bottom of the screen. * Mode Line:: Interpreting the mode line. File: emacs, Node: Point, Next: Echo Area, Prev: Screen, Up: Screen Point ===== When Emacs is running, the terminal's cursor shows the location at which editing commands will take effect. This location is called "point". Other commands move point through the text, so that you can edit at different places in it. While the cursor appears to point AT a character, point should be thought of as BETWEEN two characters; it points BEFORE the character that the cursor appears on top of. Sometimes people speak of "the cursor" when they mean "point", or speak of commands that move point as "cursor motion" commands. Terminals have only one cursor, and when output is in progress it must appear where the typing is being done. This does not mean that point is moving. It is only that Emacs has no way to show you the location of point except when the terminal is idle. If you are editing several files in Emacs, each file has its own point location. A file that is not being displayed remembers where point is so that it can be seen when you look at that file again. When there are multiple text windows, each window has its own point location. The cursor shows the location of point in the selected window. This also is how you can tell which window is selected. If the same buffer appears in more than one window, point can be moved in each window independently. The term `point' comes from the character `.', which was the command in TECO (the language in which the original Emacs was written) for accessing the value now called `point'. File: emacs, Node: Echo Area, Next: Mode Line, Prev: Point, Up: Screen The Echo Area ============= The line at the bottom of the screen (below the mode line) is the "echo area". It is used to display small amounts of text for several purposes. "Echoing" means printing out the characters that you type. Emacs never echoes single-character commands, and multi-character commands are echoed only if you pause while typing them. As soon as you pause for more than a second in the middle of a command, all the characters of the command so far are echoed. This is intended to "prompt" you for the rest of the command. Once echoing has started, the rest of the command is echoed immediately when you type it. This behavior is designed to give confident users fast response, while giving hesitant users maximum feedback. You can change this behavior by setting a variable (*note Display Vars::.). If a command cannot be executed, it may print an "error message" in the echo area. Error messages are accompanied by a beep or by flashing the screen. Also, any input you have typed ahead is thrown away when an error happens. Some commands print informative messages in the echo area. These messages look much like error messages, but they are not announced with a beep and do not throw away input. Sometimes the message tells you what the command has done, when this is not obvious from looking at the text being edited. Sometimes the sole purpose of a command is to print a message giving you specific information. For example, the command `C-x =' is used to print a message describing the character position of point in the text and its current column in the window. Commands that take a long time often display messages ending in `...' while they are working, and add `done' at the end when they are finished. The echo area is also used to display the "minibuffer", a window that is used for reading arguments to commands, such as the name of a file to be edited. When the minibuffer is in use, the echo area begins with a prompt string that usually ends with a colon; also, the cursor appears in that line because it is the selected window. You can always get out of the minibuffer by typing `C-g'. *Note Minibuffer::. File: emacs, Node: Mode Line, Prev: Echo Area, Up: Screen The Mode Line ============= Each text window's last line is a "mode line" which describes what is going on in that window. When there is only one text window, the mode line appears right above the echo area. The mode line is in inverse video if the terminal supports that, starts and ends with dashes, and contains text like `Emacs: SOMETHING'. If a mode line has something else in place of `Emacs: SOMETHING', then the window above it is in a special subsystem such as Dired. The mode line then indicates the status of the subsystem. Normally, the mode line has the following appearance: --CH-Emacs: BUF (MAJOR MINOR)----POS------ This gives information about the buffer being displayed in the window: the buffer's name, what major and minor modes are in use, whether the buffer's text has been changed, and how far down the buffer you are currently looking. CH contains two stars `**' if the text in the buffer has been edited (the buffer is "modified"), or `--' if the buffer has not been edited. Exception: for a read-only buffer, it is `%%'. BUF is the name of the window's chosen "buffer". The chosen buffer in the selected window (the window that the cursor is in) is also Emacs's selected buffer, the one that editing takes place in. When we speak of what some command does to "the buffer", we are talking about the currently selected buffer. *Note Buffers::. POS tells you whether there is additional text above the top of the screen, or below the bottom. If your file is small and it is all on the screen, POS is `All'. Otherwise, it is `Top' if you are looking at the beginning of the file, `Bot' if you are looking at the end of the file, or `NN%', where NN is the percentage of the file above the top of the screen. MAJOR is the name of the "major mode" in effect in the buffer. At any time, each buffer is in one and only one of the possible major modes. The major modes available include Fundamental mode (the least specialized), Text mode, Lisp mode, and C mode. *Note Major Modes::, for details of how the modes differ and how to select one. MINOR is a list of some of the "minor modes" that are turned on at the moment in the window's chosen buffer. `Fill' means that Auto Fill mode is on. `Abbrev' means that Word Abbrev mode is on. `Ovwrt' means that Overwrite mode is on. *Note Minor Modes::, for more information. `Narrow' means that the buffer being displayed has editing restricted to only a portion of its text. This is not really a minor mode, but is like one. *Note Narrowing::. `Def' means that a keyboard macro is being defined. *Note Keyboard Macros::. Some buffers display additional information after the minor modes. For example, Rmail buffers display the current message number and the total number of messages. Compilation buffers and Shell mode display the status of the subprocess. In addition, if Emacs is currently inside a recursive editing level, square brackets (`[...]') appear around the parentheses that surround the modes. If Emacs is in one recursive editing level within another, double square brackets appear, and so on. Since this information pertains to Emacs in general and not to any one buffer, the square brackets appear in every mode line on the screen or not in any of them. *Note Recursive Edit::. Emacs can optionally display the time and system load in all mode lines. To enable this feature, type `M-x display-time'. The information added to the mode line usually appears after the file name, before the mode names and their parentheses. It looks like this: HH:MMpm L.LL [D] (Some fields may be missing if your operating system cannot support them.) HH and MM are the hour and minute, followed always by `am' or `pm'. L.LL is the average number of running processes in the whole system recently. D is an approximate index of the ratio of disk activity to cpu activity for all users. The word `Mail' appears after the load level if there is mail for you that you have not read yet. Customization note: the variable `mode-line-inverse-video' controls whether the mode line is displayed in inverse video (assuming the terminal supports it); `nil' means no inverse video. The default is File: emacs, Node: Characters, Next: Keys, Prev: Screen, Up: Top The Emacs Character Set ======================= GNU Emacs uses the ASCII character set, which defines 128 different character codes. Some of these codes are assigned graphic symbols such as `a' and `='; the rest are control characters, such as `Control-a' (also called `C-a' for short). `C-a' gets its name from the fact that you type it by holding down the CTRL key and then pressing `a'. There is no distinction between `C-a' and `C-A'; they are the same character. Some control characters have special names, and special keys you can type them with: RET, TAB, LFD, DEL and ESC. The space character is usually referred to below as SPC, even though strictly speaking it is a graphic character whose graphic happens to be blank. Emacs extends the 7-bit ASCII code to an 8-bit code by adding an extra bit to each character. This makes 256 possible command characters. The additional bit is called Meta. Any ASCII character can be made Meta; examples of Meta characters include `Meta-a' (`M-a', for short), `M-A' (not the same character as `M-a', but those two characters normally have the same meaning in Emacs), `M-RET', and `M-C-a'. For traditional reasons, `M-C-a' is usually called `C-M-a'; logically speaking, the order in which the modifier keys CTRL and META are mentioned does not matter. Some terminals have a META key, and allow you to type Meta characters by holding this key down. Thus, `Meta-a' is typed by holding down META and pressing `a'. The META key works much like the SHIFT key. Such a key is not always labeled META, however, as this function is often a special option for a key with some other primary purpose. If there is no META key, you can still type Meta characters using two-character sequences starting with ESC. Thus, to enter `M-a', you could type `ESC a'. To enter `C-M-a', you would type `ESC C-a'. ESC is allowed on terminals with Meta keys, too, in case you have formed a habit of using it. Emacs believes the terminal has a META key if the variable `meta-flag' is non-`nil'. Normally this is set automatically according to the termcap entry for your terminal type. However, sometimes the termcap entry is wrong, and then it is useful to set this variable yourself. *Note Variables::, for how to do this. Emacs buffers also use an 8-bit character set, because bytes have 8 bits, but only the ASCII characters are considered meaningful. ASCII graphic characters in Emacs buffers are displayed with their graphics. LFD is the same as a newline character; it is displayed by starting a new line. TAB is displayed by moving to the next tab stop column (usually every 8 columns). Other control characters are displayed as a caret (`^') followed by the non-control version of the character; thus, `C-a' is displayed as `^A'. Non-ASCII characters 128 and up are displayed with octal escape sequences; thus, character code 243 (octal), also called `M-#' when used as an input character, is displayed as `\243'. File: emacs, Node: Keys, Next: Commands, Prev: Characters, Up: Top A "complete key"--where `key' is short for "key sequence"--is a sequence of keystrokes that are understood by Emacs as a unit, as a single command (possibly undefined). Most single characters constitute complete keys in the standard Emacs command set; there are also some multi-character keys. Examples of complete keys are `C-a', `X', RET, `C-x C-f' and `C-x 4 C-f'. A "prefix key" is a sequence of keystrokes that are the beginning of a complete key, but not a whole one. Prefix keys and complete keys are collectively called "keys". A prefix key is the beginning of a series of longer sequences that are valid keys; adding any single character to the end of the prefix gives a valid key, which could be defined as an Emacs command, or could be a prefix itself. For example, `C-x' is standardly defined as a prefix, so `C-x' and the next input character combine to make a two-character key. There are 256 different two-character keys starting with `C-x', one for each possible second character. Many of these two-character keys starting with `C-x' are standardly defined as Emacs commands. Notable examples include `C-x C-f' and `C-x s' (*note Files::.). Adding one character to a prefix key does not have to form a complete key. It could make another, longer prefix. For example, `C-x 4' is itself a prefix that leads to 256 different three-character keys, including `C-x 4 f', `C-x 4 b' and so on. It would be possible to define one of those three-character sequences as a prefix, creating a series of four-character keys, but we did not define any of them this way. By contrast, the two-character sequence `C-f C-k' is not a key, because the `C-f' is a complete key in itself. It's impossible to give `C-f C-k' an independent meaning as a command as long as `C-f' retains its meaning. `C-f C-k' is two commands. All told, the prefix keys in Emacs are `C-c', `C-x', `C-h', `C-x 4', and ESC. But this is not built in; it is just a matter of Emacs's standard key bindings. In customizing Emacs, you could make new prefix keys, or eliminate these. *Note Key Bindings::. Whether a sequence is a key can be changed by customization. For example, if you redefine `C-f' as a prefix, `C-f C-k' automatically becomes a key (complete, unless you define it too as a prefix). Conversely, if you remove the prefix definition of `C-x 4', then `C-x 4 f' (or `C-x 4 ANYTHING') is no longer a key.