This section describes a number of basic concepts, which will be used again and again in the following descriptions. Most of it should be familiar to EMACS users. New users are advised not to get stuck reading this section, because most of the information will become clear the first time you play with the editor on a computer.

Screen Layout

MicroEMACS divides the screen into two areas. The very last line on the screen, which is used to display messages and ask one line questions, is called the echo line . Typing in the echo line is like typing commands to the operating system. More details later in the section The Echo Line.

The remainder of the screen is filled with text windows . When MicroEMACS is first started, there will be one or two text windows, depending on how many files you specify on the invocation line. If there is only one window, it fills the screen. If there are two windows, each occupies half the screen. Windows can be created, deleted, and adjusted in size using MicroEMACS commands.

Mode Lines

The last line of a window (the line, usually in reverse video, that starts with MicroEMACS) is the mode line for the window. It contains information about what is being displayed in the window. Mode lines separate windows from each other and from the echo line.

Four important bits of information are displayed in the mode line. These are the buffer mode (if any) in parentheses, the buffer name , the file name , and the buffer changed flag .

A window is always displaying a buffer. The name of the buffer being displayed in the window is shown in the mode line, right after the MicroEMACS and the buffer mode.

A buffer may have a file associated with it. Usually this is the last file read into or written from the buffer. If a file is associated with the buffer, the name of the file is displayed in the mode line, prefixed by File:. On operating systems in which file names are case insensitive (for example, VMS) the file name will always be in lower case.

MicroEMACS knows if a buffer has been changed since it was last written to its associated file. It informs you of this fact by displaying a * in the mode line immediately to the left of the MicroEMACS string.

Keyboard Conventions

Internally, MicroEMACS represents keyboard characters in a special 11 bit code. This code consists of 8 bits of character data (ASCII plus whatever characters your terminal puts in the right side graphics set), and 3 flags, the CONTROL flag, the META flag, and the CTLX flag. Combinations of the three flags are possible, with the exception that META and CTLX cannot be set at the same time.

This manual represents 11 bit characters in a standard way. If you have a character A, then that character with the CONTROL bit set is written as C-A. That character with the META bit set is written as M-A. That character with the CTLX bit set is written as C-X A. If both the META and CONTROL bits are set, it is written as M-C-A. If both the CTLX and CONTROL bits are set, it is written as C-X C-A.

Terminals (usually) cannot deal directly deal with the 11 bit character set. Characters with the flag bits set are entered by prefixing the desired character with another character, as follows:

• To get a character with the CONTROL bit set, hold down the CTRL key while entering the character. An alternative method is to prefix the character with Control-^ (the word Control here, and in the next few examples, means the key marked Control or CTRL on the ASCII keyboard).

• To get a character with the META bit set, prefix the character with Control-[, Escape, or ESC. An alternative method that works on FlexOS is to hold down the ALT key while entering the character. This method also works on PC-DOS, but only with ALT-A through ALT-Z.

• To get a character with the CTLX bit set, prefix the character with Control-X.

• To get a character with the CONTROL and META bits set, prefix the character with Control-\. An alternative method is to prefix the character with ESC, then hold down CTRL while entering the character.

• Those of you who understand ASCII are probably asking what you get if you prefix a character with Control-]. This character is not a prefix; it is reserved for future use as an "exit from recursive editing level" command.

CONTROL characters are very important, so there is a shorthand way of typing them, as follows:

• Characters between Control-@ (Control-Space on some keyboards) and Control-Z are mapped to the characters @ through Z with the CONTROL bit set.

• Characters between Control-a and Control-z are mapped to the characters A through Z with the CONTROL bit set.

This shorthand means that that M-C-V, for example, can be entered either as ESC followed by Control-V, or as Control-\ followed by V. As another example, C-X C-B is entered as Control-X followed by Control-B.

The PC Keyboard

MicroEMACS understands all of the cursor keypad and function keys on PC compatible machines, and the equivalent keys on other machines that run FlexOS (such as the VME/10). These keys include the function keys (F1-F10), shifted function keys (S-F1 to S-F10), cursor keys (Up, Down, Left, Right, PgUp, PgDn, Home, End), Delete, and Insert. These keys may be combined with the ALT and CTRL keys.

On PCs, you can use the ALT key as the META flag, instead of the ESC key. For example, the M-L command (lower-word) can be executed in either of two ways:

• Hit ESC followed by L.

• Hold down ALT and hit L.

On PC-DOS and Linux, the ALT key only works with alphabetic characters (A through Z). Using ALT and CTRL together is also not supported.

On FlexOS, the ALT key works with both alpha and non-alpha characters, and simultaneously with the CTRL key. Thus, the command M-C-V (display-version) can be executed by holding down ALT and CTRL, while pressing V (not an easy task, in this writer's opinion).

On the VME/10, some of the cursor keys are not available, due to the inherent physical limitations of the keyboard itself.

See the Wall Chart section of this manual for the predefined bindings of some the special PC keys.

The Zenith Z-19/29 Keyboard

MicroEMACS treats the numeric keypad on the Z-19/29 similarly to the EDT/VMS customizations in common use at DRI. It does this by putting the terminal in "alternate keypad mode", so that the keypad produces escape sequences instead of numbers. The arrow keys (2, 4, 6 and 8) move one line or one character at a time; when shifted they move by pages or word. When preceded by the F6 key (BLUE on Z-19), the arrow keys move to the beginning or end of the current line or buffer. The 5 key is the same as C-S (forw-search), and shift-5 is search-again. See the Wall Chart section of this manual for further key bindings for the Z-19/29.

Not all of the key bindings that allow the shifted arrows to work like EDT are built into MicroEMACS. This is because they conflict with the traditional definitions of M-B and M-C. Therefore, these rebindings are placed in a profile called edt.pro. If you want MicroEMACS to read these bindings when it starts up, and you don't care about losing the old meanings of M-B and M-C, then copy edt.pro to the default profile name, as described below in the Profiles section.

The VT-100 Keyboard

MicroEMACS understands the arrow keys and the keypad on VT-100 style keyboards. Only the PF1 through PF4 keys on the keypad have any special meaning; the digits, the - key, and the , key are treated just like the non keypad versions of those characters. The Enter key is treated exactly like the Return key.

The arrow keys may be used for moving around. The left arrow is the same as C-B, the right arrow is the same as C-F, the up arrow is the same as C-P, and the down arrow is the same as C-N.

The four function keys are command keys. The PF1 key is the same as M-X (the PF1 key is where the Gold key normally resides on DEC products, so it is a good choice for the key that asks for extended commands). The PF2 key is the same as C-Q (quote character). The PF3 key is the same as C-S (search forward). The PF4 key is the same as C-R (search reverse). These assignments have not been proven optimal, so they may get changed in the future.

The LK201 Keyboard

The escape key, used in all META commands, is very poorly placed on the LK201 keyboard. To make typing a bit easier, the grave accent is also considered to be a META prefix on the LK201; the grave accent is right where you expect the escape key to be located. A grave accent must be quoted to exter it into the text.

The arrow keys and all of the keys on the keypad work just like they do on the VT-100 keyboard.

The keys immediately above the arrow keys try to do what their name implies. Next Screen is the same as C-V. Prev Screen is the same as M-V. Select is the same as C-@ (set mark). Remove is the same as C-W (kill region). Insert here is the same as C-Y (yank from killbuffer). Find is the same as C-S (search forward).

The F6, F7, F8, F9, F10, and F14 keys are unused. The F11 is escape, which is a META prefix key. The F12 key is backspace. The F13 key is linefeed.

The Help key is unused. The Do key is the same as C-X E (execute keyboard macro).

The F17 key is the same as C-X P (previous window). The F18 key is the same as C-X N (next window). The F19 key is the same as C-X Z (grow window). The F20 key is the same as C-X C-Z (shrink window).

Key Bindings

Normally when you type a key, MicroEMACS attempts to interprets the key as a command. Internally, MicroEMACS keeps a table of each possible key, and the command assocated with that key. This association is called the "key binding."
Even text keys, such as the letters, numbers, and punctuation, are "bound" to a command called "ins-self" that just inserts the key that invoked it into the text.

Not all commands are bound to a particular key. These commands can still be entered by using the (M-X) (ESC X) "extended-command" prefix, or by binding them to a key with the "bind-to-key" command. See the section Key Binding Commands for more information.

In subsequent sections, the command descriptions will give not only the key that the command is normally bound to, but also the command name, which is useful when you want to change the key bindings.

The Echo Line

The echo line has two purposes; displaying messages and asking one line questions.

Two types of messages are displayed in the echo line. Informational messages tell you something useful, but do not imply in any way that something is wrong. These messages are always enclosed in square brackets ([ and ]). Error messages indicate that something has prevented a command from being executed. They are never enclosed in square brackets, and will be accompanied by a beep from the terminal's bell if the sound of the bell is not too obnoxious.

The echo line is cleared by the next keystroke.

The echo line is also used for asking and answering questions. After the prompt, you can type any characters you like. The reply is always terminated by a Return. Before you commit to the reply, you can edit the reply using the following characters:

• Backspace or Rubout: delete the character to the left of the cursor.

• Control-A: move the cursor to the beginning of the line.

• Control-B: move the cursor one character to the left.

• Control-D: delete the character under the cursor.

• Control-E: move the cursor to end of the line.

• Control-F: move the cursor one character to the right.

• Control-K: delete from the cursor to the end of the line.

• Control-Q: enter the next character literally into the line (useful for entering control characters).

• Control-U: delete the entire line.

You can also abort the command in progress by typing Control-G. Command processors are designed to ask all questions before doing nasty things, so that you will never do damage by aborting a command.

The echo line supports autocompletion. If you are entering a command name, a filename, or a buffer name, you can use the Space or Tab keys to tell MicroEMACS to complete as much of the entry as possible, based on what you have entered so far. If you are entering a filename, pressing Control-S will fill in the directory part of the current buffer's filename, making it easier to find a file in the same directory. Pressing the ? or Control-D keys will open a new temporary window containing the possible list of choices.

If you are entering a search string, pressing Control-S will fill in the previous search string.

Command Arguments

All commands can be given a numeric argument. Most commands use this argument as a repeat count. Commands can tell if an argument has been supplied, and will use a default argument if no user argument is present. Usually, the default argument is 1.

A C-U preceding a command always introduces an argument.

If a numeric argument is just a string of C-U characters, then the value of the argument is 4^(number of C-U characters), where "^" means "to the power." Therefore C-U is 4, C-U C-U is 16, C-U C-U C-U is 256, and so on. Some commands care if an argument is present, but don't look at its value; the C-U character is a good way to say "here is an argument".

If there is a signed decimal number after the string of C-U characters it specifies the value of the argument. In this case the number of C-U characters does not matter. An argument of 10 can be represented by C-U 10, C-U C-U 10, or even C-U C-U C-U C-U 10.

Dot, Mark, and the Region

Most editing commands act on the character or characters surrounding the current location in the current buffer. The thing that marks the current location is always called dot . The dot always points between two characters. This isn't the way that the cursor works on most display terminals, so, by convention, dot is always immediately to the left of the character on which the hardware cursor is placed.

There is also a second remembered position in the buffer, called the mark . There are commands that set the value of mark.

Some commands act on a block of text called the region . The region is all of the characters between dot and mark. The relative positions of dot and mark do not matter.