;按键1清屏。
;按键2设置前景色。
;按键3设置背景色。
;按键4向上滚动一行。

;(1)清屏：将显存中当前屏幕中的字符设为空格符；
;(2)设置前景色：设置显存中当前屏幕中处于奇地址的属性字节的第0、1、2位；
;(3)设置背景色：设置显存中当前屏幕中处于击地址的属性字节的第4、5、6位；
;(4)向上滚动一行：依次将第n+1行的内容复制到第n行处；最后一行为空。
assume cs:code,ds:data

data segment
        dw 8 dup(0)
        
code segment
start:
                        mov ax,data
                        mov ds,ax                                ;设ds
                        mov ax,0
                        mov es,ax                                ;设es
                        mov ax,es:[9*4]                        
                        mov ds:[0],ax                        ;保存int9的ip
                        mov ax,es:[9*4+2]
                        mov ds:[2],ax                        ;保存int9的cs
                        mov ax,offset INT9                
                        mov es:[9*4],ax                        ;子程序偏移放在int9的ip中
                        mov es:[9*4+2],cs                ;cs放在int9cs中
;===============================================================================================
;显示A~Z26个字符                        
                        mov ax,0b800h 
            mov es,ax                ;重设es 
            mov di,160*12+40*2        ;设di 
            mov al,'A' 
        s2: mov es:[di],al            ;屏幕显示 
            call short sleep                ;延时 
            inc al                    ;al+1 
            cmp al,'Z' 
            jna s2                    ;不大于'Z'进循环 
                        mov ax,4c00h
                        int 21h
;============================================================================
;延时                
        sleep:  push ax                    ;延时 
            push dx 
            mov ax,0 
            mov dx,01f00h   
         s1:    sub ax,1 
            sbb dx,0 
            cmp ax,0 
            jne s1 
            cmp dx,0 
            jne s1 
             
            pop dx 
            pop ax 
            ret 
;==========================================================================
;新的int9中断
INT9:                
                        push ax                                        ;保存ax
                        pushf                                        ;标志寄存器压栈
                        pushf
                        pop ax
                        and ah,11111100b                ;TF=0,IF=0
                        call dword ptr ds:[0]        ;调用原9号中断
                        in al,60h                                ;读60h端口内容
                        cmp al,02h                                ;和1的扫描码对比
                        je PASS1                                ;一样就跳
                        cmp al,03h                                ;和2的扫描码对比
                        je PASS2                                ;一样就跳
                        cmp al,04h                                ;和3的扫描码对比
                        je PASS3                                ;一样就跳
                        cmp al,05h                                ;和4的扫描码对比
                        je PASS4                                ;一样就跳
                        
                        pop ax
                        iret                                         ;没有一样的退出the9
        PASS4:        jmp near ptr mypass4
;=======================================================================================
;清屏                        
        PASS1:        push si
                        push es
                        push cx
                        push ax
                        mov ax,0b800h
                        mov es,ax                                        ;设es        
                        mov cx,2000                                        ;设cx
                        mov si,0                                        ;设si
        sub1:        mov es:[si],byte ptr ' '        ;
                        add si,2
                        loop sub1                                        ;全屏设' '
                        pop ax
                        pop cx
                        pop es
                        pop si
                        pop ax
                        iret
;======================================================================
;设前景色                        
                        
        PASS2:        push si
                        push es
                        push cx
                        push ax
                        mov ax,0b800h
                        mov es,ax                                        ;设es
                        mov si,1                                        ;设si
                        mov cx,2000                                        ;设cx
                        mov bl,es:[si]                                ;用bl保存当然颜色参数
                        and bl,00000111b                        ;把前景色提出来
                        cmp bl,7                                        ;于7比
                        jb ss2                                                ;小于跳转
                        sub bl,bl                                        ;大于或等于清零
        ss2:        inc bl                                                ;加1
        sub2:        and byte ptr es:[si],11111000b        ;把前景清零
                        or es:[si],bl                                        ;前景用bl
                        add si,2                                                ;下一个颜色位置
                        loop sub2                                        
                        pop ax
                        pop cx
                        pop es
                        pop si
                        pop ax
                        iret 
;====================================================================================
;设背景色        
        PASS3:        push ax
                        push si
                        push es
                        push cx
                        mov ax,0b800h
                        mov es,ax                                        ;设es
                        mov si,1                                        ;设si
                        mov bh,es:[si]                                ;用bh做背景色
                        shr bh,1                                        
                        shr bh,1
                        shr bh,1
                        shr bh,1                                        ;右移4位
                        cmp bh,7                                        ;于7比
                        jb ss3                                                ;小于跳                                        ;
                        sub bh,bh                                        ;不小于清零
        ss3:        inc bh                                                ;加1变色
                        mov cx,2000                                        ;2000个颜色位置
        sub3:        add byte ptr es:[si],10001111b        ;背景色清零
                        shl bh,1
                        shl bh,1
                        shl bh,1
                        shl bh,1                                                ;bh左移4位
                        or byte ptr es:[si],bh                        ;用bh做背景色
                        add si,2                                                ;下一个颜色位置
                        loop sub3
                        pop cx
                        pop es
                        pop si
                        pop ax
                        pop ax
                        iret
;========================================================================================
;向上滚动一行
mypass4:        push ax
                        push si
                        push di
                        push es
                        push ds
                        push cx
                        mov ax,0b800h                
                        mov es,ax                                ;设es
                        mov ds,ax                                ;设ds
                        mov di,0                                ;设di
                        mov si,160                                ;设si
                        cld                                                ;DF零0，正方向
        int4:        mov cx,160                                ;设cx
                        rep movsb                                ;ds:si到es:di
                        
                        cmp si,160*25                        ;
                        ja out1                                        ;到最后一行下面就退出
                        jmp short int4

        out1:
                        pop cx
                        pop ds
                        pop es
                        pop di
                        pop si
                        pop ax
                        pop ax
                        iret
                        
code ends
end start