The init file contains one or more Lisp function call
expressions. Each consists of a function name followed by
arguments, all surrounded by parentheses. For example, (setq
fill-column 60) represents a call to the function setq which is
used to set the variable fill-column (see Filling) to 60.
The second argument to setq is an expression for the new value
of the variable. This can be a constant, a variable, or a function call
expression. In the init file, constants are used most of the time.
They can be:
If a sequence of digits is followed by a period and another sequence of digits, it is interpreted as a floating point number.
The number prefixes ‘#b’, ‘#o’, and ‘#x’ are supported to
represent numbers in binary, octal, and hexadecimal notation (or radix).
Newlines and special characters may be present literally in strings. They can also be represented as backslash sequences: ‘\n’ for newline, ‘\b’ for backspace, ‘\r’ for return, ‘\t’ for tab, ‘\f’ for formfeed (control-l), ‘\e’ for escape, ‘\\’ for a backslash, ‘\"’ for a double-quote, or ‘\ooo’ for the character whose octal code is ooo. Backslash and double-quote are the only characters for which backslash sequences are mandatory.
You can use ‘\C-’ as a prefix for a control character, as in
‘\C-s’ for ASCII Control-S, and ‘\M-’ as a prefix for
a Meta character, as in ‘\M-a’ for Meta-A or ‘\M-\C-a’ for
Control-Meta-A.
?x, ?\n, ?\", ?\). Note that
strings and characters are not interchangeable in Lisp; some contexts
require one and some contexts require the other.
t stands for `true'.
nil stands for `false'.