INT 10H 06H: Scroll Up / Clear Screen Rectangle
Expects: AH 06H
AL number of lines to scroll in (0=blank entire rectangle)
BH video attribute to be used on blank line(s)
CH,CL row,clm of lower-right corner of rectangle to scroll/blank
DH,DL row,clm of upper-left corner of rectangle to scroll/blank
Info: You may use this to scroll screen text up; that is, move each
line of text higher on the screen and add one or more blank lines
at the bottom.
This fn can be used to scroll a rectangular subset of the screen.
It may also be used to clear the entire screen or any rectangular
Notes: ž The standard way to clear the screen is to set DX to 0000H, CL
to 0040:[004a]-1 (usually 79), CH to 0040: (usually 24),
BH to 07H (white-on black video attribute), and AL to 00H (to
clear the entire screen).
ž To scroll the text up (as when the user presses the down
arrow), set CX and DX to cover the entire screen (or a
rectangular subset), and set AL to 1.
ž CGAs: When most of the screen is a color other than black, you
should avoid using this function for scrolling. Original CGA
BIOSes display an annoying flicker with each scroll operation.
It is usually best to write a special routine to move the text
yourself. See CGA Video Snow and CLS Flash.
See Also: INT 10H 07H (scroll down)
INT 10H: Video Services