** Emacs has a new facility to help users manage the many<BR>
customization options.  To make a Lisp program work with this facility,
you need to use the new macros defgroup and defcustom.
<P>
You use defcustom instead of defvar, for defining a user option
variable.  The difference is that you specify two additional pieces of
information (usually): the "type" which says what values are
legitimate, and the "group" which specifies the hierarchy for
customization.
<P>
Thus, instead of writing
<P>
    (defvar foo-blurgoze nil
      "*Non-nil means that foo will act very blurgozely.")
<P>
you would now write this:
<P>
    (defcustom foo-blurgoze nil
      "*Non-nil means that foo will act very blurgozely."
      :type 'boolean
      :group foo)
<P>
The type `boolean' means that this variable has only
two meaningful states: nil and non-nil.  Other type values
describe other possibilities; see the manual for Custom
for a description of them.
<P>
The "group" argument is used to specify a group which the option
should belong to.  You define a new group like this:
<P>
    (defgroup ispell nil
      "Spell checking using Ispell."
      :group 'processes)
<P>
The "group" argument in defgroup specifies the parent group.  The root
group is called `emacs'; it should not contain any variables itself,
but only other groups.  The immediate subgroups of `emacs' correspond
to the keywords used by C-h p.  Under these subgroups come
second-level subgroups that belong to individual packages.
<P>
Each Emacs package should have its own set of groups.  A simple
package should have just one group; a more complex package should
have a hierarchy of its own groups.  The sole or root group of a
package should be a subgroup of one or more of the "keyword"
first-level subgroups.
<P>