11.8 Other Help Commands

C-h i (info) runs the Info program, which is used for browsing through structured documentation files. The entire Emacs manual is available within Info. Eventually all the documentation of the GNU system will be available. Type h after entering Info to run a tutorial on using Info.

With a numeric argument, C-h i selects an Info buffer with the number appended to the default ‘*info*’ buffer name (e.g. ‘*info*<2>’). This is useful if you want to browse multiple Info manuals simultaneously. If you specify just C-u as the prefix argument, C-h i prompts for the name of a documentation file. This way, you can browse a file which doesn't have an entry in the top-level Info menu. It is also handy when you need to get to the documentation quickly, and you know the exact name of the file.

There are two special help commands for accessing Emacs documentation through Info. C-h F function <RET> enters Info and goes straight to the documentation of the Emacs function function. C-h K key enters Info and goes straight to the documentation of the key key. These two keys run the commands Info-goto-emacs-command-node and Info-goto-emacs-key-command-node. You can use C-h K to find the documentation of a menu item: just select that menu item when C-h K prompts for a key.

C-h F and C-h K know about commands and keys described in manuals other than the Emacs manual. Thus, they make it easier to find the documentation of commands and keys when you are not sure which manual describes them, like when using some specialized mode.

When editing a program, if you have an Info version of the manual for the programming language, you can use the command C-h S (info-lookup-symbol) to refer to the manual documentation for a symbol (keyword, function or variable). The details of how this command works depend on the major mode.

If something surprising happens, and you are not sure what commands you typed, use C-h l (view-lossage). C-h l displays the last 100 command characters you typed in. If you see commands that you don't know, you can use C-h c to find out what they do.

To review messages that recently appeared in the echo area, use C-h e (view-echo-area-messages). This displays the buffer *Messages*, where those messages are kept.

Emacs has numerous major modes, each of which redefines a few keys and makes a few other changes in how editing works. C-h m (describe-mode) displays documentation on the current major mode, which normally describes all the commands that are changed in this mode.

C-h b (describe-bindings) and C-h s (describe-syntax) present other information about the current Emacs mode. C-h b displays a list of all the key bindings now in effect, showing the local bindings defined by the current minor modes first, then the local bindings defined by the current major mode, and finally the global bindings (see Key Bindings). C-h s displays the contents of the syntax table, with explanations of each character's syntax (see Syntax).

You can get a similar list for a particular prefix key by typing C-h after the prefix key. (There are a few prefix keys for which this does not work—those that provide their own bindings for C-h. One of these is <ESC>, because <ESC> C-h is actually C-M-h, which marks a defun.)