;  shows int 10h
        mov     dx, 0           ;sets row and col to zero
        mov     bh, 0           ;set video page
        mov     ah, 2           ;set cursor
        int     10h             ;sets cursor to upper left corner
        mov     ah, 9           ;write characters
        mov     cx, 2000        ;num of characters on screen
        mov     al, ' '         ;put out spaces
        mov     bl, 40h         ;red background
        mov     bh, 0           ;video page
        int     10h

        int     20h