Keys and their RepresentationThis section describes the legal Epsilon keys, and the representation that Epsilon uses when referring to keys and reading command files. The key representation used when writing extension language programs appears in Keys.
Epsilon recognizes hundreds of distinct key combinations you can type on the keyboard (including control and alt keys). You can bind a command to each of these keys. Each key can also function as a prefix key, allowing even more key combinations. By default, Ctrl-x and Ctrl-c serve as prefix keys.
First, the keyboard provides the standard 128
ASCII characters. All the white keys in the central part of the PC
keyboard, possibly in combination with the Shift and Control keys,
generate ASCII characters. So do the <Esc>, <Backspace>,
<Tab>, and <Enter> keys. They generate Control
You can get an additional 256 keys by holding down the Alt key while typing the above keys. In Epsilon, you can also enter an Alt key by typing an <Esc> before the key. Similarly, the Control-^ key says to interpret the following key as if you had held down the Control key while typing that key.
If you want to enter an actual <Esc> or Control-^ instead, type a Control-Q before it. The Ctrl-q key "quotes" the following key against special interpretations. See Bindings.
In command files and some other contexts, Epsilon represents Control keys by C-<char>, with <char> replaced by the original key. Thus Control-t appears as C-T. The case of the <char> doesn't matter for control characters when Epsilon reads a command file, but the C- must appear in upper case. The Delete character (ASCII code 127) appears as C-?. Note that this has nothing to do with the key marked "Del" on the PC keyboard. The Alt keys appear with A- appended to the beginning of their usual symbol, as in A-f for Alt-f and A-C-h for Alt-Control-H.
Epsilon represents function keys by F-1, F-2, ... F-63. The F must appear in upper case. You can also specify the Shift, Control, and Alt versions of function keys, in any combination. In a command file, you specify the Shift, Control, and Alt versions with a prefix of S-, C-, or A-, respectively. For example, Epsilon refers to the key you get by holding down the Shift and Alt keys and pressing the F8 key as A-S-F-8.
Keys on the cursor keypad work in a similar way. Epsilon recognizes several synonyms for these keys, as listed in the table. Epsilon generally uses the first name listed, but will accept any of the names from a command file.
Epsilon normally treats the shifted versions of these keys (and others) as synonyms for the unshifted versions. When you press Shift-<Left>, Epsilon runs the command bound to <Left>. The commands bound to most of these keys then examine the Shift key and decide whether to begin or stop selecting text. (Holding down the shift key while using the cursor keys is one way to select text in Epsilon.)
Epsilon refers to the numeric keypad keys with the names given in the table.
In a command file, you can also represent keys by their conventional names, by writing <Newline> or <Escape>, or by number, writing <#0> for the null character ^@, for example. Epsilon understands the same key names here as in regular expression patterns (see the table in Entering Special Characters).
Macros defined in command files may also use the syntax
Several keys on the PC keyboard act as synonyms for other keys: the
grey keys *,