求王爽汇编语言实验17答案真的好想看下没思路了...

Question

求王爽 汇编语言 实验17答案
真的好想看下 没思路了...

Answer 1

assume cs:code,ds:data
data segment
strd db 60000 dup (0) ;读取磁盘内容到这里
data ends
code segment
start:mov ax,data
mov ds,ax
mov si,offset strd
mov ax,0
mov es,ax
push si
pop es:[204h] ;保存data段偏移地址
push ds
pop es:[206h] ;保存data段地址
push cs
pop ds
call setup7ch ;安装7ch中断
mov ax,0
mov es,ax
cli
push es:[13h*4] ;复制13h中断偏移
pop es:[200h]
push es:[13h*4+2] ;复制13h中断段
pop es:[202h]
mov word ptr es:[7ch*4],208h ;7ch中断入口
mov word ptr es:[7ch*4+2],0
sti
mov ah,0
mov bx,9
int 7ch
mov ax,4c00h
int 21h
setup7ch proc ;安装7ch子程序
push ax
push si
push di
push cx
mov si,offset new7ch
mov ax,0
mov es,ax
mov di,208h
mov cx,offset new7chend - offset new7ch
cld
rep movsb
pop cx
pop di
pop si
pop ax
ret
setup7ch endp
new7ch:jmp short nstart ;7ch中断例程
strc db 'i love this world!'
nstart:push cs
pop ds
push ds
pop es
push bx
cmp ah,1 ;0为读,1为写
jne fread
fwrite:pop bx
call setfld ;根据王爽老师提供的逻辑扇区算法(计算逻辑扇区到物理扇区的子程序).
mov bx,offset strc
mov al,1
mov ah,3
pushf
call dword ptr es:[200h] ;调用旧int 13h例程,此时入口地址在0:200H
iret
fread:pop bx
call setfld
mov ax,es:[206h] ; es 指向DATA段地址
mov es,ax
mov bx,es:[204h] ;bx 指向data 偏移地址
mov al,1
mov ah,2
pushf
call dword ptr cs:[200h]
iret
setfld proc ;计算逻辑扇区到物理扇区的子程序,入口参数 BX ,出口参数:cl 扇区号,CH磁道号,dl软驱,dh柱面号
mov ax,0
mov ax,bx
xor dx,dx
mov bx,1440
div bx
xchg ah,al
push ax
mov ax,dx
xor dx,dx
mov bh,0
mov bl,18
div bl
mov ch,al
xchg ah,al
mov ah,0
inc ax
mov cl,al
pop dx
ret
setfld endp
new7chend:nop
code ends
end start