On graphical displays, Emacs can indicate the buffer boundaries in the fringes. If you enable this feature, the first line and the last line are marked with angle images in the fringes. This can be combined with up and down arrow images which say whether it is possible to scroll the window.
The buffer-local variable indicate-buffer-boundaries controls
how the buffer boundaries and window scrolling is indicated in the
fringes. If the value is
right, both angle and
arrow bitmaps are displayed in the left or right fringe, respectively.
If value is an alist (see Association Lists in the Emacs
Lisp Reference Manual), each element
position) specifies the position of one of the indicators. The
indicator must be one of
down, or t which specifies the default position for the
indicators not present in the alist. The position is one of
nil which specifies not to show
((top . left) (t . right)) places the top angle
bitmap in left fringe, the bottom angle bitmap in right fringe, and
both arrow bitmaps in right fringe. To show just the angle bitmaps in
the left fringe, but no arrow bitmaps, use
((top . left)
(bottom . left)).