汇编语言(王爽 第三版)实验十六

    assume cs:code

    stack segment
    db 128 dup (0)
    stack ends
    
    code segment
start:    mov ax,stack
    mov ss,ax
    mov sp,128

    mov ax,cs
    mov ds,ax
    
    mov ax,0
    mov es,ax

    mov di,204h
    mov si,offset int9
    mov cx,offset int9end-offset int9
    cld
    rep movsb

    push es:[9*4]
    pop es:[200h]
    push es:[9*4+2]
    pop es:[202h]

    cli
    mov word ptr es:[9*4],204h
    mov word ptr es:[9*4+2],0
    sti

    mov ax,4c00h
    int 21h

int9:    push ax
    push bx
    push cx
    push es
    in al,60h
    pushf
    call dword ptr cs:[200h]
    cmp al,02
    je do1
    cmp al,03
    je do2
    cmp al,04
    je do3
    cmp al,05
    je do4
    jmp short int9ret

do1:    call sub1
    jmp short int9ret
do2:    call sub2
    jmp short int9ret
do3:    call sub3
    jmp short int9ret
do4:    call sub4
    jmp short int9ret

int9ret:pop es
    pop cx
    pop bx
    pop ax
    iret
    
sub1:    push bx
    push cx
    push es
    mov bx,0b800h
    mov es,bx
    mov bx,0
    mov cx,2000
sub1s:    mov byte ptr es:[bx],‘ ‘
    add bx,2
    loop sub1s
    pop es
    pop cx
    pop bx
    ret

sub2:    push ax
    push bx
    push cx
    push es
    mov bx,0b800h
    mov es,bx
    mov bx,1
    mov cx,2000
    mov al,00000001b
sub2s:    and byte ptr es:[bx],11111000b
    or es:[bx],al
    add bx,2
    loop sub2s
    pop es
    pop cx
    pop bx
    pop ax
    ret

sub3:    push ax
    push bx
    push cx
    push es
    mov bx,0b800h
    mov es,bx
    mov bx,1
    mov cx,2000
    mov al,01110000b
sub3s:    and byte ptr es:[bx],10001111b
    or es:[bx],al
    add bx,2
    loop sub3s
    pop es
    pop cx
    pop bx
    pop ax
    ret

sub4:    push cx
    push si
    push di
    push es
    push ds

    mov si,0b800h
    mov es,si
    mov ds,si
    mov si,160
    mov di,0
    cld
    mov cx,24
sub4s:    push cx
    mov cx,160
    rep movsb
    pop cx
    loop sub4s
    mov cx,80
    mov si,0
sub4s1:    mov byte ptr [160*24+si],‘ ‘
    add si,2
    loop sub4s1
    pop ds
    pop es
    pop di
    pop si
    pop cx
    ret
int9end:nop
    code ends
    end start