z, ^F, ^B:
If count is not specified, it shall default to the window
edit option - 2.
Write lines from the edit buffer starting at:
(the current line) - ((count - 2) / 2)
until:
(((count + 1) / 2) * 2) - 1
lines, or the last line in the edit buffer has been written. A
line consisting of the smaller of the number of columns in the
display divided by two or 40 ``-'' characters shall be written
immediately before and after the specified is written. These two
lines shall count against the total number of lines to be written.
A blank line shall be written after the last line is written.
z, ^F and ^B all behave identically.
^D: Display the next scroll value lines, change the current line.
^U: Change the current line, do nothing else.
^E, ^Y: Do nothing.
^L: Clear the screen and redisplay the current line.
H, L, M:
Move to the first nonblank of the current line and do nothing
else.
