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使用call指令直接调用标号不需要计算偏移量
- assume cs:code
- code segment
- start: mov ax,0
- mov es,ax
- mov di,200H
- mov ax,cs
- mov ds,ax
- mov si,offset setscreen
- mov cx,offset int7ch_end-offset setscreen
- cld
- rep movsb
- mov word ptr es:[7ch*4],200h
- mov word ptr es:[7ch*4+2],0h
- mov ax,4c00h
- int 21h
- ; 功能: 调用指定的子程序
- ; 参数: (ah)=功能号(0-3)
- ; (al)=颜色值(0-7)
- setscreen: cmp ah,0
- je do1
- cmp ah,1
- je do2
- cmp ah,2
- je do3
- cmp ah,3
- je do4
- jmp short sret
- do1: call sub1
- jmp short sret
- do2: call sub2
- jmp short sret
- do3: call sub3
- jmp short sret
- do4: call sub4
- sret: iret
- ; 清屏
- 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
- ; 设置前景色
- sub2: push bx
- push cx
- push es
- mov bx,0b800h
- mov es,bx
- mov bx,1
- mov cx,2000
- sub2s: and byte ptr es:[bx],11111000b ; 前景色置0
- or es:[bx],al ; 放入颜色值
- add bx,2
- loop sub2s
- pop es
- pop cx
- pop bx
- ret
- ; 设置背景色
- sub3: push bx
- push cx
- push es
- mov cl,4
- shl al,cl
- mov bx,0b800h
- mov es,bx
- mov bx,1
- mov cx,2000
- sub3s: and byte ptr es:[bx],10001111b ; 背景色置0
- or es:[bx],al ; 放入背景色值
- add bx,2
- loop sub3s
- pop es
- pop cx
- pop bx
- ret
- ; 向上滚动一行
- sub4: push cx
- push si
- push di
- push es
- push ds
- mov si,0b800h
- mov es,si
- mov ds,si
- mov si,160 ; ds:si指向n+1行
- mov di,0 ; es:di指向n行
- cld
- mov cx,24
- sub4s: push cx
- mov cx,160
- rep movsb ; n+1行覆盖到n行上
- pop cx
- loop sub4s
- mov cx,80
- mov si,0
- sub4s1: mov byte ptr [160*24+si],' ' ; 最后一行清空
- add si,2
- loop sub4s1
- pop ds
- pop es
- pop di
- pop si
- pop cx
- ret
- int7ch_end:nop
- code ends
- end start
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