Commit 973cefd2 authored by Richard M. Stallman's avatar Richard M. Stallman

Explain "prefix arg". Explain how it can be a flag.

parent 262c8cea
......@@ -191,18 +191,23 @@ is by typing C-u and then the digits before you type the command. If
you have a META (or EDIT or ALT) key, there is another alternative way
to enter a numeric argument: type the digits while holding down the
META key. We recommend learning the C-u method because it works on
any terminal.
any terminal. The numeric argument is also called a "prefix argument",
because you type the argument before the command it applies to.
For instance, C-u 8 C-f moves forward eight characters.
>> Try using C-n or C-p with a numeric argument, to move the cursor
to a line near this one with just one command.
Most commands use the numeric argument as a repeat count. Certain
exceptional commands use it differently. C-v and M-v are among the
exceptions. When given an argument, they scroll the screen up or down
by that many lines, rather than by a screenfuls. For example, C-u 4
C-v scrolls the screen by 4 lines.
Most commands use the numeric argument as a repeat count, but some
commands use it in some other way. Several commands (but none of
those you have learned so far) use it as a flag--the presence of a
prefix argument, regardless of its value, makes the command do
something different.
C-v and M-v are another kind of exception. When given an argument,
they scroll the screen up or down by that many lines, rather than by a
screenful. For example, C-u 8 C-v scrolls the screen by 8 lines.
>> Try typing C-u 8 C-v now.
......
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