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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 (see section Multiple 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.
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'.
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 (see section Variables Controlling Display).
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. See section The Minibuffer.
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. See section Using Multiple 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. See section 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. See section 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. See section Narrowing. `Def' means that a keyboard macro is being defined. See section 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. See section Recursive Editing Levels.
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 user 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 t.
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