bug#3752: 23.0.95; I can not understant a sentence in Intro to Emacs Lisp .

--text follows this line--
In section 8.5.1 in the manual `Introduction to Emacs Lisp'.  I can
not understant what is `readily settable variable' in second
paragraph.  Thanks . [email protected]

In GNU Emacs 23.0.95.1 (i686-pc-linux-gnu, GTK+ Version 2.14.7)
 of 2009-06-21 on laptop
Windowing system distributor `The X.Org Foundation', version 11.0.10503000
configured using `configure  '--prefix=/usr' '--build=i686-pc-linux-gnu'
'--host=i686-pc-linux-gnu' '--mandir=/usr/share/man'
'--infodir=/usr/share/info' '--datadir=/usr/share' '--sysconfdir=/etc'
'--localstatedir=/var/lib' '--program-suffix=-emacs-23'
'--infodir=/usr/share/info/emacs-23' '--with-sound' '--with-x'
'--without-toolkit-scroll-bars' '--with-gif' '--with-jpeg' '--with-png'
'--with-rsvg' '--with-tiff' '--with-xpm' '--with-xft' '--without-libotf'
'--without-m17n-flt' '--with-x-toolkit=gtk' '--without-hesiod'
'--without-kerberos' '--without-kerberos5' '--with-gpm' '--with-dbus'
'build_alias=i686-pc-linux-gnu' 'host_alias=i686-pc-linux-gnu' 'CFLAGS=-O2
-march=pentium-m -pipe' 'LDFLAGS=-Wl,-O1''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: en_US.UTF-8
  value of $LC_CTYPE: zh_CN.UTF-8
  value of $LC_MESSAGES: en_US.UTF-8
  value of $LC_MONETARY: en_US.UTF-8
  value of $LC_NUMERIC: en_US.UTF-8
  value of $LC_TIME: en_US.UTF-8
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=SCIM
  locale-coding-system: utf-8-unix
  default-enable-multibyte-characters: t

Minor modes in effect:
  reftex-mode: t
  TeX-fold-mode: t
  flyspell-mode: t
  TeX-source-specials-mode: t
  minibuffer-depth-indicate-mode: t
  icicle-mode: t
  show-paren-mode: t
  display-time-mode: t
  global-auto-complete-mode: t
  auto-complete-mode: t
  desktop-save-mode: t
  yas/minor-mode: t
  auto-image-file-mode: t
  outline-minor-mode: t
  shell-dirtrack-mode: t
  tooltip-mode: t
  tool-bar-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  global-auto-composition-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: t
  abbrev-mode: t

Recent input:
<drag-mouse-1> <help-echo> <down-mouse-1> <mouse-1>
<down-mouse-5> <mouse-5> <help-echo> <help-echo> <down-mouse-1>
<help-echo> <help-echo> <help-echo> <down-mouse-4>
<mouse-4> <down-mouse-1> <mouse-movement> <mouse-movement>
<help-echo> <drag-mouse-1> <help-echo> <down-mouse-1>
<mouse-1> <down-mouse-1> <mouse-1> <help-echo> <help-echo>
<down-mouse-4> <mouse-4> <double-down-mouse-4> <double-mouse-4>
<down-mouse-5> <mouse-5> <down-mouse-4> <mouse-4> <help-echo>
<tool-bar> <Exit> <help-echo> <tool-bar> <Exit> <help-echo>
<tool-bar> <Exit> <help-echo> <help-echo> <help-echo>
<tool-bar> <kill-buffer> <down-mouse-4> <mouse-4> <down-mouse-4>
<mouse-4> <double-down-mouse-4> <double-mouse-4> <down-mouse-4>
<mouse-4> <double-down-mouse-4> <double-mouse-4> <help-echo>
<down-mouse-3> <mouse-3> <help-echo> <down-mouse-1>
<mouse-1> <help-echo> <menu-bar> <buffer> C-h <help-echo>
<tool-bar> <kill-buffer> <menu-bar> <buffer> C-h <help-echo>
<tool-bar> <kill-buffer> <help-echo> <menu-bar> <buffer>
C-h <help-echo> <help-echo> <help-echo> <help-echo>
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo>
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo>
<help-echo> <menu-bar> <file> <kill-buffer> <help-echo>
<menu-bar> <buffer> C-h <help-echo> <help-echo> <help-echo>
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo>
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo>
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo>
<help-echo> <menu-bar> <file> <kill-buffer> <help-echo>
<help-echo> <menu-bar> <buffer> C-h <help-echo> <help-echo>
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo>
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo>
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo>
<help-echo> <help-echo> <help-echo> <menu-bar> <file>
<kill-buffer> <help-echo> <help-echo> <help-echo> <help-echo>
<menu-bar> <buffer> C-h <down-mouse-4> <mouse-4> <double-down-mouse-4>
<double-mouse-4> <help-echo> <help-echo> <help-echo>
<help-echo> <help-echo> <help-echo> <help-echo> <menu-bar>
<file> <kill-buffer> <help-echo> <help-echo> <help-echo>
<help-echo> <help-echo> <down-mouse-3> <mouse-3> <help-echo>
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo>
<help-echo> <help-echo> <tool-bar> <latex> <help-echo>
<help-echo> <down-mouse-5> <mouse-5> <down-mouse-1>
<mouse-movement> <mouse-1> <return> <right> <right>
<right> <right> <right> <right> <right> <right> <down-mouse-1>
<mouse-1> SPC <delete> <delete> <delete> <delete> <delete>
<delete> <delete> <down-mouse-1> <mouse-1> <down-mouse-1>
<mouse-1> SPC <help-echo> <help-echo> <help-echo> <tool-bar>
<save-buffer> <down-mouse-1> <mouse-movement> <mouse-movement>
<drag-mouse-1> C-c C-p C-r <help-echo> <down-mouse-1>
<mouse-1> <help-echo> <down-mouse-3> <mouse-3> <help-echo>
<down-mouse-1> <mouse-movement> <mouse-movement> <drag-mouse-1>
<help-echo> <down-mouse-1> <mouse-movement> <mouse-1>
% <help-echo> <down-mouse-3> <mouse-3> <backspace>
<help-echo> <tool-bar> <undo> <help-echo> <tool-bar>
<undo> <help-echo> <help-echo> <help-echo> <down-mouse-1>
<help-echo> <mouse-movement> <mouse-1> <help-echo>
<down-mouse-1> <mouse-movement> <help-echo> <mouse-movement>
<mouse-movement> <drag-mouse-1> <help-echo> C-c C-p
C-c C-r <down-mouse-1> <mouse-1> <help-echo> <help-echo>
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo>
<help-echo> <help-echo> <help-echo> M-x r e p o <tab>
r <tab> <return>

Recent messages:
Type `C-c C-l' to display results of compilation.
Quit
Saving file /media/bak/latex/_region_.tex...
Wrote /media/bak/latex/_region_.tex
Type `C-c C-l' to display results of compilation.
locating previews...
Mark set
Type `C-c C-l' to display results of compilation.
Undo! [2 times]
Computing completion candidates...