auto-fill-mode by default?
To turn on auto-fill-mode just once for one buffer, use M-x
auto-fill-mode.
To turn it on for every buffer in a certain mode, you must use the hook
for that mode. For example, to turn on auto-fill mode for all
text buffers, including the following in your .emacs file:
(add-hook 'text-mode-hook 'turn-on-auto-fill)
If you want auto-fill mode on in all major modes, do this:
(setq-default auto-fill-function 'do-auto-fill)