Compatibility
-------------

   Gnus was designed to be fully compatible with GNUS.  Almost all key
bindings have been kept.  More key bindings have been added, of course,
but only in one or two obscure cases have old bindings been changed.

   Our motto is:
                         In a cloud bones of steel.


   All commands have kept their names.  Some internal functions have
changed their names.

   The `gnus-uu' package has changed drastically. *note Decoding
Articles::..

   One major compatibility question is the presence of several summary
buffers.  All variables that are relevant while reading a group are
buffer-local to the summary buffer they belong in.  Although many
important variables have their values copied into their global
counterparts whenever a command is executed in the summary buffer, this
change might lead to incorrect values being used unless you are careful.

   All code that relies on knowledge of GNUS internals will probably
fail.  To take two examples: Sorting `gnus-newsrc-alist' (or changing
it in any way, as a matter of fact) is strictly verboten.  Gnus
maintains a hash table that points to the entries in this alist (which
speeds up many functions), and changing the alist directly will lead to
peculiar results.

   Old hilit19 code does not work at all.  In fact, you should probably
remove all hilit code from all Gnus hooks (`gnus-group-prepare-hook'
and `gnus-summary-prepare-hook').  Gnus provides various integrated
functions for highlighting.  These are faster and more accurate.  To
make life easier for everybody, Gnus will by default remove all hilit
calls from all hilit hooks.  Uncleanliness!  Away!

   Packages like `expire-kill' will no longer work.  As a matter of
fact, you should probably remove all old GNUS packages (and other code)
when you start using Gnus.  More likely than not, Gnus already does
what you have written code to make GNUS do.  (Snicker.)

   Even though old methods of doing things are still supported, only the
new methods are documented in this manual.  If you detect a new method
of doing something while reading this manual, that does not mean you
have to stop doing it the old way.

   Gnus understands all GNUS startup files.

   Overall, a casual user who hasn't written much code that depends on
GNUS internals should suffer no problems.  If problems occur, please
let me know by issuing that magic command `M-x gnus-bug'.