These two functions make it easy to display all the Emacs option variables, and to change some of them if you wish.
M-x list-options displays a list of all Emacs option variables, in an Emacs buffer named `*List Options*'. Each option is shown with its documentation and its current value. Here is what a portion of it might look like:
;; exec-path: ("." "/usr/local/bin" "/usr/ucb" "/bin" "/usr/bin" "/u2/emacs/etc") *List of directories to search programs to run in subprocesses. Each element is a string (directory name) or nil (try the default directory). ;; ;; fill-column: 75 *Column beyond which automatic line-wrapping should happen. Automatically becomes buffer-local when set in any fashion. ;;
M-x edit-options goes one step further and immediately selects the `*List Options*' buffer; this buffer uses the major mode Options mode, which provides commands that allow you to point at an option and change its value:
nil, it becomes
t; otherwise it becomes
Any changes take effect immediately, and last until you exit from Emacs.