Mercurial > hg > xemacs-beta
view man/new-users-guide/edit.texi @ 2367:ecf1ebac70d8
[xemacs-hg @ 2004-11-04 23:05:23 by ben]
commit mega-patch
configure.in: Turn off -Winline and -Wchar-subscripts.
Use the right set of cflags when compiling modules.
Rewrite ldap configuration to separate the inclusion of lber
(needed in recent Cygwin) from the basic checks for the
needed libraries.
add a function for MAKE_JUNK_C; initially code was added to
generate xemacs.def using this, but it will need to be rewritten.
add an rm -f for junk.c to avoid weird Cygwin bug with cp -f onto
an existing file.
Sort list of auto-detected functions and eliminate unused checks for
stpcpy, setlocale and getwd.
Add autodetection of Cygwin scanf problems
BETA: Rewrite section on configure to indicate what flags are important
and what not.
digest-doc.c, make-dump-id.c, profile.c, sorted-doc.c: Add proper decls for main().
make-msgfile.c: Document that this is old junk.
Move proposal to text.c.
make-msgfile.lex: Move proposal to text.c.
make-mswin-unicode.pl: Convert error-generating code so that the entire message will
be seen as a single unrecognized token.
mule/mule-ccl.el: Update docs.
lispref/mule.texi: Update CCL docs.
ldap/eldap.c: Mule-ize.
Use EXTERNAL_LIST_LOOP_2 instead of deleted EXTERNAL_LIST_LOOP.
* XEmacs 21.5.18 "chestnut" is released.
---------------------------------------------------------------
MULE-RELATED WORK:
---------------------------------------------------------------
---------------------------
byte-char conversion
---------------------------
buffer.c, buffer.h, insdel.c, text.c: Port FSF algorithm for byte-char conversion, replacing broken
previous version. Track the char position of the gap. Add
functions to do char-byte conversion downwards as well as upwards.
Move comments about algorithm workings to internals manual.
---------------------------
work on types
---------------------------
alloc.c, console-x-impl.h, dump-data.c, dump-data.h, dumper.c, dialog-msw.c, dired-msw.c, doc.c, editfns.c, esd.c, event-gtk.h, event-msw.c, events.c, file-coding.c, file-coding.h, fns.c, glyphs-eimage.c, glyphs-gtk.c, glyphs-msw.c, glyphs-shared.c, glyphs-x.c, glyphs.c, glyphs.h, gui.c, hpplay.c, imgproc.c, intl-win32.c, lrecord.h, lstream.c, keymap.c, lisp.h, libsst.c, linuxplay.c, miscplay.c, miscplay.h, mule-coding.c, nas.c, nt.c, ntheap.c, ntplay.c, objects-msw.c, objects-tty.c, objects-x.c, print.c, process-nt.c, process.c, redisplay.h, select-common.h, select-gtk.c, select-x.c, sgiplay.c, sound.c, sound.h, sunplay.c, sysfile.h, sysdep.c, syswindows.h, text.c, unexnt.c, win32.c, xgccache.c: Further work on types. This creates a full set of types for all
the basic semantics of `char' that I have so far identified, so that
its semantics can always be identified for the purposes of proper
Mule-safe code, and the raw use of `char' always avoided.
(1) More type renaming, for consistency of naming.
Char_ASCII -> Ascbyte
UChar_ASCII -> UAscbyte
Char_Binary -> CBinbyte
UChar_Binary -> Binbyte
SChar_Binary -> SBinbyte
(2) Introduce Rawbyte, CRawbyte, Boolbyte, Chbyte, UChbyte, and
Bitbyte and use them.
(3) New types Itext, Wexttext and Textcount for separating out
the concepts of bytes and textual units (different under UTF-16
and UTF-32, which are potential internal encodings).
(4) qxestr*_c -> qxestr*_ascii.
lisp.h: New; goes with other qxe() functions. #### Maybe goes in a
different section.
lisp.h: Group generic int-type defs together with EMACS_INT defs.
lisp.h: * lisp.h (WEXTTEXT_IS_WIDE)
New defns.
lisp.h: New type to replace places where int occurs as a boolean.
It's signed because occasionally people may want to use -1 as
an error value, and because unsigned ints are viral -- see comments
in the internals manual against using them.
dynarr.c: int -> Bytecount.
---------------------------
Mule-izing
---------------------------
device-x.c: Partially Mule-ize.
dumper.c, dumper.h: Mule-ize. Use Rawbyte. Use stderr_out not printf. Use wext_*().
sysdep.c, syswindows.h, text.c: New Wexttext API for manipulation of external text that may be
Unicode (e.g. startup code under Windows).
emacs.c: Mule-ize. Properly deal with argv in external encoding.
Use wext_*() and Wexttext. Use Rawbyte.
#if 0 some old junk on SCO that is unlikely to be correct.
Rewrite allocation code in run-temacs.
emacs.c, symsinit.h, win32.c: Rename win32 init function and call it even earlier, to
initialize mswindows_9x_p even earlier, for use in startup code
(XEUNICODE_P).
process.c: Use _wenviron not environ under Windows, to get Unicode environment
variables.
event-Xt.c: Mule-ize drag-n-drop related stuff.
dragdrop.c, dragdrop.h, frame-x.c: Mule-ize.
text.h: Add some more stand-in defines for particular kinds of conversion;
use in Mule-ization work in frame-x.c etc.
---------------------------
Freshening
---------------------------
intl-auto-encap-win32.c, intl-auto-encap-win32.h: Regenerate.
---------------------------
Unicode-work
---------------------------
intl-win32.c, syswindows.h: Factor out common options to MultiByteToWideChar and
WideCharToMultiByte. Add convert_unicode_to_multibyte_malloc()
and convert_unicode_to_multibyte_dynarr() and use. Add stuff for
alloca() conversion of multibyte/unicode.
alloc.c: Use dfc_external_data_len() in case of unicode coding system.
alloc.c, mule-charset.c: Don't zero out and reinit charset Unicode tables. This fucks up
dump-time loading. Anyway, either we load them at dump time or
run time, never both.
unicode.c: Dump the blank tables as well.
---------------------------------------------------------------
DOCUMENTATION, MOSTLY MULE-RELATED:
---------------------------------------------------------------
EmacsFrame.c, emodules.c, event-Xt.c, fileio.c, input-method-xlib.c, mule-wnnfns.c, redisplay-gtk.c, redisplay-tty.c, redisplay-x.c, regex.c, sysdep.c: Add comment about Mule work needed.
text.h: Add more documentation describing why DFC routines were not written
to return their value. Add some other DFC documentation.
console-msw.c, console-msw.h: Add pointer to docs in win32.c.
emacs.c: Add comments on sources of doc info.
text.c, charset.h, unicode.c, intl-win32.c, intl-encap-win32.c, text.h, file-coding.c, mule-coding.c: Collect background comments and related to text matters and
internationalization, and proposals for work to be done, in text.c
or Internals manual, stuff related to specific textual API's in
text.h, and stuff related to internal implementation of Unicode
conversion in unicode.c. Put lots of pointers to the comments to
make them easier to find.
s/mingw32.h, s/win32-common.h, s/win32-native.h, s/windowsnt.h, win32.c: Add bunches of new documentation on the different kinds of
builds and environments under Windows and how they work.
Collect this info in win32.c. Add pointers to these docs in
the relevant s/* files.
emacs.c: Document places with long comments.
Remove comment about exiting, move to internals manual, put
in pointer.
event-stream.c: Move docs about event queues and focus to internals manual, put
in pointer.
events.h: Move docs about event stream callbacks to internals manual, put
in pointer.
profile.c, redisplay.c, signal.c: Move documentation to the Internals manual.
process-nt.c: Add pointer to comment in win32-native.el.
lisp.h: Add comments about some comment conventions.
lisp.h: Add comment about the second argument.
device-msw.c, redisplay-msw.c: @@#### comments are out-of-date.
---------------------------------------------------------------
PDUMP WORK (MOTIVATED BY UNICODE CHANGES)
---------------------------------------------------------------
alloc.c, buffer.c, bytecode.c, console-impl.h, console.c, device.c, dumper.c, lrecord.h, elhash.c, emodules.h, events.c, extents.c, frame.c, glyphs.c, glyphs.h, mule-charset.c, mule-coding.c, objects.c, profile.c, rangetab.c, redisplay.c, specifier.c, specifier.h, window.c, lstream.c, file-coding.h, file-coding.c: PDUMP:
Properly implement dump_add_root_block(), which never worked before,
and is necessary for dumping Unicode tables.
Pdump name changes for accuracy:
XD_STRUCT_PTR -> XD_BLOCK_PTR.
XD_STRUCT_ARRAY -> XD_BLOCK_ARRAY.
XD_C_STRING -> XD_ASCII_STRING.
*_structure_* -> *_block_*.
lrecord.h: some comments added about
dump_add_root_block() vs dump_add_root_block_ptr().
extents.c: remove incorrect comment about pdump problems with gap array.
---------------------------------------------------------------
ALLOCATION
---------------------------------------------------------------
abbrev.c, alloc.c, bytecode.c, casefiddle.c, device-msw.c, device-x.c, dired-msw.c, doc.c, doprnt.c, dragdrop.c, editfns.c, emodules.c, file-coding.c, fileio.c, filelock.c, fns.c, glyphs-eimage.c, glyphs-gtk.c, glyphs-msw.c, glyphs-x.c, gui-msw.c, gui-x.c, imgproc.c, intl-win32.c, lread.c, menubar-gtk.c, menubar.c, nt.c, objects-msw.c, objects-x.c, print.c, process-nt.c, process-unix.c, process.c, realpath.c, redisplay.c, search.c, select-common.c, symbols.c, sysdep.c, syswindows.h, text.c, text.h, ui-byhand.c: New macros {alloca,xnew}_{itext,{i,ext,raw,bin,asc}bytes} for
more convenient allocation of these commonly requested items.
Modify functions to use alloca_ibytes, alloca_array, alloca_extbytes,
xnew_ibytes, etc. also XREALLOC_ARRAY, xnew.
alloc.c: Rewrite the allocation functions to factor out repeated code.
Add assertions for freeing dumped data.
lisp.h: Moved down and consolidated with other allocation stuff.
lisp.h, dynarr.c: New functions for allocation that's very efficient when mostly in
LIFO order.
lisp.h, text.c, text.h: Factor out some stuff for general use by alloca()-conversion funs.
text.h, lisp.h: Fill out convenience routines for allocating various kinds of
bytes and put them in lisp.h. Use them in place of xmalloc(),
ALLOCA().
text.h: Fill out the convenience functions so the _MALLOC() kinds match
the alloca() kinds.
---------------------------------------------------------------
ERROR-CHECKING
---------------------------------------------------------------
text.h: Create ASSERT_ASCTEXT_ASCII() and ASSERT_ASCTEXT_ASCII_LEN()
from similar Eistring checkers and change the Eistring checkers to
use them instead.
---------------------------------------------------------------
MACROS IN LISP.H
---------------------------------------------------------------
lisp.h: Redo GCPRO declarations. Create a "base" set of functions that can
be used to generate any kind of gcpro sets -- regular, ngcpro,
nngcpro, private ones used in GC_EXTERNAL_LIST_LOOP_2.
buffer.c, callint.c, chartab.c, console-msw.c, device-x.c, dialog-msw.c, dired.c, extents.c, ui-gtk.c, rangetab.c, nt.c, mule-coding.c, minibuf.c, menubar-msw.c, menubar.c, menubar-gtk.c, lread.c, lisp.h, gutter.c, glyphs.c, glyphs-widget.c, fns.c, fileio.c, file-coding.c, specifier.c: Eliminate EXTERNAL_LIST_LOOP, which does not check for circularities.
Use EXTERNAL_LIST_LOOP_2 instead or EXTERNAL_LIST_LOOP_3
or EXTERNAL_PROPERTY_LIST_LOOP_3 or GC_EXTERNAL_LIST_LOOP_2
(new macro). Removed/redid comments on EXTERNAL_LIST_LOOP.
---------------------------------------------------------------
SPACING FIXES
---------------------------------------------------------------
callint.c, hftctl.c, number-gmp.c, process-unix.c: Spacing fixes.
---------------------------------------------------------------
FIX FOR GEOMETRY PROBLEM IN FIRST FRAME
---------------------------------------------------------------
unicode.c: Add workaround for newlib bug in sscanf() [should be fixed by
release 1.5.12 of Cygwin].
toolbar.c: bug fix for problem of initial frame being 77 chars wide on Windows.
will be overridden by my other ws.
---------------------------------------------------------------
FIX FOR LEAKING PROCESS HANDLES:
---------------------------------------------------------------
process-nt.c: Fixes for leaking handles. Inspired by work done by Adrian Aichner
<adrian@xemacs.org>.
---------------------------------------------------------------
FIX FOR CYGWIN BUG (Unicode-related):
---------------------------------------------------------------
unicode.c: Add workaround for newlib bug in sscanf() [should be fixed by
release 1.5.12 of Cygwin].
---------------------------------------------------------------
WARNING FIXES:
---------------------------------------------------------------
console-stream.c: `reinit' is unused.
compiler.h, event-msw.c, frame-msw.c, intl-encap-win32.c, text.h: Add stuff to deal with ANSI-aliasing warnings I got.
regex.c: Gather includes together to avoid warning.
---------------------------------------------------------------
CHANGES TO INITIALIZATION ROUTINES:
---------------------------------------------------------------
buffer.c, emacs.c, console.c, debug.c, device-x.c, device.c, dragdrop.c, emodules.c, eval.c, event-Xt.c, event-gtk.c, event-msw.c, event-stream.c, event-tty.c, events.c, extents.c, faces.c, file-coding.c, fileio.c, font-lock.c, frame-msw.c, glyphs-widget.c, glyphs.c, gui-x.c, insdel.c, lread.c, lstream.c, menubar-gtk.c, menubar-x.c, minibuf.c, mule-wnnfns.c, objects-msw.c, objects.c, print.c, scrollbar-x.c, search.c, select-x.c, text.c, undo.c, unicode.c, window.c, symsinit.h: Call reinit_*() functions directly from emacs.c, for clarity.
Factor out some redundant init code. Move disallowed stuff
that had crept into vars_of_glyphs() into complex_vars_of_glyphs().
Call init_eval_semi_early() from eval.c not in the middle of
vars_of_() in emacs.c since there should be no order dependency
in the latter calls.
---------------------------------------------------------------
ARMAGEDDON:
---------------------------------------------------------------
alloc.c, emacs.c, lisp.h, print.c: Rename inhibit_non_essential_printing_operations to
inhibit_non_essential_conversion_operations.
text.c: Assert on !inhibit_non_essential_conversion_operations.
console-msw.c, print.c: Don't do conversion in SetConsoleTitle or FindWindow to avoid
problems during armageddon. Put #errors for NON_ASCII_INTERNAL_FORMAT
in places where problems would arise.
---------------------------------------------------------------
CHANGES TO THE BUILD PROCEDURE:
---------------------------------------------------------------
config.h.in, s/cxux.h, s/usg5-4-2.h, m/powerpc.h: Add comment about correct ordering of this file.
Rearrange everything to follow this -- put all #undefs together
and before the s&m files. Add undefs for HAVE_ALLOCA, C_ALLOCA,
BROKEN_ALLOCA_IN_FUNCTION_CALLS, STACK_DIRECTION. Remove unused
HAVE_STPCPY, HAVE_GETWD, HAVE_SETLOCALE.
m/gec63.h: Deleted; totally broken, not used at all, not in FSF.
m/7300.h, m/acorn.h, m/alliant-2800.h, m/alliant.h, m/altos.h, m/amdahl.h, m/apollo.h, m/att3b.h, m/aviion.h, m/celerity.h, m/clipper.h, m/cnvrgnt.h, m/convex.h, m/cydra5.h, m/delta.h, m/delta88k.h, m/dpx2.h, m/elxsi.h, m/ews4800r.h, m/gould.h, m/hp300bsd.h, m/hp800.h, m/hp9000s300.h, m/i860.h, m/ibmps2-aix.h, m/ibmrs6000.h, m/ibmrt-aix.h, m/ibmrt.h, m/intel386.h, m/iris4d.h, m/iris5d.h, m/iris6d.h, m/irist.h, m/isi-ov.h, m/luna88k.h, m/m68k.h, m/masscomp.h, m/mg1.h, m/mips-nec.h, m/mips-siemens.h, m/mips.h, m/news.h, m/nh3000.h, m/nh4000.h, m/ns32000.h, m/orion105.h, m/pfa50.h, m/plexus.h, m/pmax.h, m/powerpc.h, m/pyrmips.h, m/sequent-ptx.h, m/sequent.h, m/sgi-challenge.h, m/symmetry.h, m/tad68k.h, m/tahoe.h, m/targon31.h, m/tekxd88.h, m/template.h, m/tower32.h, m/tower32v3.h, m/ustation.h, m/vax.h, m/wicat.h, m/xps100.h: Delete C_ALLOCA, HAVE_ALLOCA, STACK_DIRECTION,
BROKEN_ALLOCA_IN_FUNCTION_CALLS. All of this is auto-detected.
When in doubt, I followed recent FSF sources, which also have
these things deleted.
author | ben |
---|---|
date | Thu, 04 Nov 2004 23:08:28 +0000 |
parents | abe6d1db359e |
children | e43d0da85762 |
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@comment node-name, next, previous, up @node Edit, Customization Basics, Windows and Menus, Top @chapter Basic Editing Commands @kindex C-h t @findex help-with-tutorial This chapter will introduce you to some basic editing commands. You can also learn the basic editing commands by typing @kbd{Control-h t} (@code{help-with-tutorial} OR by selecting @b{Emacs Tutorial} from the @b{Help} menu on the menu bar. Most of the Emacs commands will use the @key{CONTROL} key or the @key{META} key. The following abbreviations will be used for the @key{CONTROL} and @key{META} key in this manual: @table @kbd @item C-<chr> This means that you should hold down the @key{CONTROL} key while typing @kbd{<chr>}. For example, if the command is @kbd{C-g}, you should hold the @key{CONTROL} key and type @key{g}. @item M-<chr> This means that you should hold down the @kbd{META} key while typing @kbd{<chr>}. If there is no @kbd{META} key on your keyboard, use the @kbd{ESC} key instead. For example, if the command is @kbd{M-x}, then type @kbd{ESC}, release it and type @kbd{x}. @end table The following abbreviations will be used for some other keys: @table @key @item SPC Space bar. @item RET Return key. @item LFD Linefeed key. @item TAB Tab. @item ESC Escape. @item SFT Shift. @end table @comment node-name, next, previous, up @menu * Insert:: Insert text in Emacs by simply typing at the cursor position. * Cursor Position:: Moving Around the cursor in the buffer, * Erase:: Different commands for erasing text * Numeric Argument:: Giving Numeric Arguments to commands * Undo:: Undoing Changes made by mistake @end menu @node Insert, Cursor Position, Edit, Edit @section Inserting Text @cindex insertion @cindex overstrike To insert printing characters into the text you are editing, just type them. Emacs will automatically insert the characters that you type into the buffer at the cursor. The cursor moves forward, but if you prefer to have text characters replace (overwrite) existing text characters, you can enable the @b{Overstrike} option from the @b{Options} menu in the menu bar. @kindex DEL @cindex deletion To @dfn{delete} text you have just inserted, use @key{DEL}. @key{DEL} deletes the character @var{before} the cursor (not the one that the cursor is on top of or under; that is the character @var{after} the cursor). The cursor and all characters after it move backwards. Therefore, if you type a printing character and then type @key{DEL}, they cancel out. @kindex RET @cindex newline @findex auto-fill-mode To end a line and start typing a new one, type @key{RET}. This inserts a newline character in the buffer. If point is in the middle of a line, @key{RET} splits the line. Typing @key{DEL} when the cursor is at the beginning of a line rubs out the newline before the line, thus joining the line with the preceding line. Emacs automatically splits lines when they become too long, if you turn on a special mode called @dfn{Auto Fill} mode. @xref{Filling,,,xemacs,XEmacs User's Manual}, for information on using Auto Fill mode. @comment node-name, next, previous, up @node Cursor Position, Erase, Insert, Edit @section Moving Around @cindex cursor control @cindex cursor position The following commands will allow you to move the cursor around the screen. The actual function names corresponding to these commands are given in parenthesis. You can also invoke these commands by typing @kbd{M-x <function name>}. You can do this for any command in XEmacs. @kindex C-a @kindex C-e @kindex C-fx @kindex C-b @kindex C-n @kindex C-p @kindex C-v @kindex M-v @kindex C-t @kindex M-> @kindex M-< @findex beginning-of-line @findex end-of-line @findex forward-char @findex backward-char @findex next-line @findex previous-line @findex transpose-chars @findex beginning-of-buffer @findex end-of-buffer @findex goto-char @findex goto-line @table @kbd @item C-b Move the cursor backward one character (@code{backward-char}). @item C-f Move the cursor forward one character (@code{forward-char}). @item C-p Move the cursor up one line vertically (@code{previous-line}). @item C-n Move the cursor down one line vertically (@code{next-line}). @item C-a Move the cursor to the beginning of the line (@code{beginning-of-line}). @item C-e Move the cursor to the end of the line (@code{end-of-line}). @item M-f @findex forward-word Move the cursor forward one word (@code{forward-word}). @item M-b @findex backward-word Move the cursor backward one word (@code{backward-word}). @item M-< Move the cursor to the top of the buffer (@code{beginning-of-buffer}). @item M-> Move the cursor to the end of the buffer (@code{end-of-buffer}). @item M-x goto-char RET <number> RET To enable this command type @kbd{M-x goto-char}, and hit @key{RETURN} key. In the @dfn{echo area} you will see: @example Goto char: @end example @noindent You should then type in a number right after the colon and hit the @kbd{RETURN} key again. After reading a number @var{n} this command will move the cursor to character number @var{n}. Position 1 is the beginning of the buffer. For example, if you type @kbd{M-x goto-char RET 200 RET}, then the cursor will move to the 200th character starting from the beginning of the buffer. @item M-x goto-line RET <number> RET @cindex goto-line To enable this command type @kbd{M-x goto-line}, and hit the @key{RETURN} key. After you see @kbd{Goto line:} in the @dfn{echo area}, type in a number @var{n} and hit @key{RETURN} key again. This command will position the cursor on the nth line starting from the beginning of the buffer. @item M-x what-line RET This command will display the current line number in the echo area. @end table @comment node-name, next, previous, up @node Erase, Numeric Argument, Cursor Position, Edit @section Erasing Text @cindex erasing @cindex deleting @kindex C-d @kindex C-k @kindex M-d @kindex M-DEL @kindex M-k @kindex M-z @findex delete-backward-char @findex delete-char @findex kill-line @findex kill-word @findex backward-kill-word @findex kill-sentence @findex zap-to-char @table @kbd @item @key{DEL} If you press @key{DEL} i.e. the @dfn{delete} key, it will delete the character before the cursor (@code{delete-backward-char}). @item C-d This will delete the character after the cursor (@code{delete-char}). @item C-k Kill to the end of the line (@code{kill-line}). If you kill the line by mistake you can @dfn{yank} or @samp{paste} it back by typing @kbd{C-y}. @xref{Moving Text}, for more information on yanking. @item M-d Kill forward to the end of the next word (@code{kill-word}). @item M-@key{DEL} Kill back to the beginning of the previous word (@code{backward-kill-word}). @item M-k Kill to the end of current sentence (@code{kill-sentence}). @item M-z @var{char} Kill up to next occurrence of @var{char} (@code{zap-to-char}). To use this command type @kbd{M-z}. You will see the following statement in the echo area : @example Zap to char: @end example Type any char and press the @key{RET} key. For example, if you type @samp{p} then the entire text starting from the position of the cursor until the first occurrence of @samp{p} is killed. @end table @comment node-name, next, previous, up @node Numeric Argument, Undo, Erase, Edit @section Giving Numeric Arguments @cindex numeric argument @cindex digit argument @cindex negative argument @kindex C-u @kindex M-@t{-} Any Emacs command can be given a @dfn{numeric argument}. Some commands interpret the argument as a repetition count. For example, if you want to move forward ten characters, you could type @kbd{C-f} ten times. However, a more efficient way to do this would be to give an argument of ten to the key @kbd{C-f} (the command @code{forward-char}, move forward one character). Negative arguments are also allowed. Often they tell a command to move or act backwards. For example, if you want to move down ten lines, type the following: @example C-u 10 C-n RET @end example @noindent After you press @key{RET} key, the cursor will move ten lines downward. You can also type: @example M-10 C-n RET @end example @noindent Both @kbd{C-u} and @kbd{M-} allow you to give numeric arguments. If you want to move ten lines backward, you can also give negative arguments, like: @example C-u -10 C-n RET @end example @noindent OR you could also type: @example M--10 C-n RET @end example @noindent You can obviously use @kbd{C-b} to move backward rather than giving negative arguments to @kbd{C-n}. @xref{Numeric Arguments,,,xemacs,XEmacs User's Manual}, for more information on numeric arguments. @comment node-name, next, previous, up @node Undo, , Numeric Argument, Edit @section Undoing Changes @cindex undo @cindex mistakes, correcting When you are editing a buffer, you might type something by mistake. Emacs allows you to undo all changes you make to a buffer (but not more than 8000 characters). Each buffer in Emacs keeps a record of the changes made to it individually, so the undo command applies to the current buffer. There are two undo commands: @table @kbd @kindex C-x u @item C-x u Undo one batch of changes (usually, one command's worth). (@code{undo}). @item C-_ The same as above, but this command might not be obvious to type on some keyboards so it might be better to use the above command. @end table @xref{Undoing Changes,,,xemacs,XEmacs User's Manual}, for more information on undoing changes.