汇编清屏

Interrupt:   10h     Functions:  06h and 07h

Initializes a specified window of the display to ASCII blank
characters with a given attribute, or scrolls the contents of
a window by a specified number of lines.

Input
AH = 06h to scroll up
   = 07h to scroll down
AL = Number of lines to scroll (if zero, entire window is blanked)
BH = Attribute to be used for blanked area
CH = y coordinate, upper left corner of window
CL = x coordinate, upper left corner of window
DH = y coordinate, lower right corner of window
DL = x coordinate, lower right corner of window