INT 10h,  06h (6)        Scroll Window Up

    Scrolls a specified window upward a specified number of lines.

       On entry:      AH         06h
                      AL         Number of lines to scroll (if 0, clear entire
                                 window)
                      BH         Display attribute for blank lines
                      CH         Row number of upper left corner
                      CL         Column number of upper left corner
                      DH         Row number of lower right corner
                      DL         Column number of lower right corner

       Returns:       None

       Registers destroyed:      AX, SP, BP, SI, DI

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    Lines are inserted at the bottom with all lines moving up. The new
    lines are filled with blank characters of a specified display
    attribute (value in BH). The lines that disappear at the top of the
    window are lost.

       Notes:         If the number of lines to scroll is specified as 0,
                      the entire window is filled with blanks.

                      Use Service 07h to scroll the window down.

                      This service affects only the currently active
                      display page.