split-window-below

split-window-below is an interactive compiled Lisp function in `window.el'.

It is bound to C-x 2, <menu-bar> <file> <new-window-below>.

(split-window-below &optional SIZE)

Split the selected window into two windows, one above the other.
The selected window is above. The newly split-off window is
below and displays the same buffer. Return the new window.

If optional argument SIZE is omitted or nil, both windows get the
same height, or close to it. If SIZE is positive, the upper
(selected) window gets SIZE lines. If SIZE is negative, the
lower (new) window gets -SIZE lines.

If the variable `split-window-keep-point' is non-nil, both
windows get the same value of point as the selected window.
Otherwise, the window starts are chosen so as to minimize the
amount of redisplay; this is convenient on slow terminals.