(emacs.info) Arguments

 
 Numeric Arguments
 =================
 
    In mathematics and computer usage, the word "argument" means "data
 provided to a function or operation."  You can give any Emacs command a
 "numeric argument" (also called a "prefix argument").  Some commands
 interpret the argument as a repetition count.  For example, `C-f' with
 an argument of ten moves forward ten characters instead of one.  With
 these commands, no argument is equivalent to an argument of one.
 Negative arguments tell most such commands to move or act in the
 opposite direction.
 
    If your terminal keyboard has a <META> key, the easiest way to
 specify a numeric argument is to type digits and/or a minus sign while
 holding down the <META> key.  For example,
      M-5 C-n
 
 would move down five lines.  The characters `Meta-1', `Meta-2', and so
 on, as well as `Meta--', do this because they are keys bound to
 commands (`digit-argument' and `negative-argument') that are defined to
 contribute to an argument for the next command.  Digits and `-'
 modified with Control, or Control and Meta, also specify numeric
 arguments.
 
    Another way of specifying an argument is to use the `C-u'
 (`universal-argument') command followed by the digits of the argument.
 With `C-u', you can type the argument digits without holding down
 modifier keys; `C-u' works on all terminals.  To type a negative
 argument, type a minus sign after `C-u'.  Just a minus sign without
 digits normally means -1.
 
    `C-u' followed by a character which is neither a digit nor a minus
 sign has the special meaning of "multiply by four."  It multiplies the
 argument for the next command by four.  `C-u' twice multiplies it by
 sixteen.  Thus, `C-u C-u C-f' moves forward sixteen characters.  This
 is a good way to move forward "fast," since it moves about 1/5 of a line
 in the usual size screen.  Other useful combinations are `C-u C-n',
 `C-u C-u C-n' (move down a good fraction of a screen), `C-u C-u C-o'
 (make "a lot" of blank lines), and `C-u C-k' (kill four lines).
 
    Some commands care only about whether there is an argument, and not
 about its value.  For example, the command `M-q' (`fill-paragraph') with
 no argument fills text; with an argument, it justifies the text as well.
 ( Filling, for more information on `M-q'.)  Plain `C-u' is a
 handy way of providing an argument for such commands.
 
    Some commands use the value of the argument as a repeat count, but do
 something peculiar when there is no argument.  For example, the command
 `C-k' (`kill-line') with argument N kills N lines, including their
 terminating newlines.  But `C-k' with no argument is special: it kills
 the text up to the next newline, or, if point is right at the end of
 the line, it kills the newline itself.  Thus, two `C-k' commands with
 no arguments can kill a nonblank line, just like `C-k' with an argument
 of one.  ( Killing, for more information on `C-k'.)
 
    A few commands treat a plain `C-u' differently from an ordinary
 argument.  A few others may treat an argument of just a minus sign
 differently from an argument of -1.  These unusual cases are described
 when they come up; they are always for reasons of convenience of use of
 the individual command.
 
    You can use a numeric argument to insert multiple copies of a
 character.  This is straightforward unless the character is a digit; for
 example, `C-u 6 4 a' inserts 64 copies of the character `a'.  But this
 does not work for inserting digits; `C-u 6 4 1' specifies an argument
 of 641, rather than inserting anything.  To separate the digit to
 insert from the argument, type another `C-u'; for example, `C-u 6 4 C-u
 1' does insert 64 copies of the character `1'.
 
    We use the term "prefix argument" as well as "numeric argument" to
 emphasize that you type the argument before the command, and to
 distinguish these arguments from minibuffer arguments that come after
 the command.
Info Catalog
(emacs.info) Position Info
(emacs.info) Basic
(emacs.info) Repeating
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