4.3BSD/usr/contrib/emacs/lisp/window.elc

(defun split-window-vertically (arg) "\
Split current window into two windows, one above the other.
This window becomes the uppermost of the two, and gets
ARG lines.  No arg means split equally." (interactive "P") (byte-code "ÀˆÂ	…Ã	!\"‡" [nil arg split-window prefix-numeric-value] 4))

(defun split-window-horizontally (arg) "\
Split current window into two windows side by side.
This window becomes the leftmost of the two, and gets
ARG columns.  No arg means split equally." (interactive "P") (byte-code "ÀˆÃ	…Ä	!
#‡" [nil arg t split-window prefix-numeric-value] 5))

(defun enlarge-window-horizontally (arg) "\
Make current window ARG columns wider." (interactive "p") (byte-code "ˆÃ	\"‡" [arg t nil enlarge-window] 3))

(defun shrink-window-horizontally (arg) "\
Make current window ARG columns narrower." (interactive "p") (byte-code "ˆÃ	\"‡" [arg t nil shrink-window] 3))

(define-key ctl-x-map "2" (quote split-window-vertically))

(define-key ctl-x-map "5" (quote split-window-horizontally))

(define-key ctl-x-map "}" (quote enlarge-window-horizontally))

(define-key ctl-x-map "{" (quote shrink-window-horizontally))