(defun scroll-up-one-line ()
  (interactive)
  (scroll-up 1))

(defun scroll-down-one-line ()
  (interactive)
  (scroll-down 1))

(defun scroll-bg-up-one-line ()
  (interactive)
  (scroll-up 1)
  (next-line 1))

(defun scroll-bg-down-one-line ()
  (interactive)
  (scroll-down 1)
  (previous-line 1))

(global-set-key [(control ?.)]   'scroll-up-one-line)        ; C-.
(global-set-key [(control ?;)]   'scroll-down-one-line)      ; C-;
(global-set-key [(control ?>)]   'scroll-bg-up-one-line)        ; C->
(global-set-key [(control ?:)]   'scroll-bg-down-one-line)      ; C-: