源程序:
assume cs:code, ds:data data segment db 77h,65h,6ch,63h,6fh,6dh,65h,20h,74h,6fh,20h,6dh,61h,73h,6dh,21h ;ASCII码 db 2h,24h,71h ;颜色 data ends code segment start: mov ax,data mov ds,ax mov ax,0b872h ;显示器中心区域的显存地址 mov es,ax mov cx,16 ;16个字符循环16次 mov di,0 ;data段中字符的偏移地址 mov si,0 ;代表行数的偏移地址 mov bx,16 ;data段中颜色的偏移地址 s: mov al,ds:[di] ;字符存入寄存器低位 mov ah,ds:[bx] ;第一行颜色属性存入高位 mov es:[si],ax ;第一行写入显存地址 mov ah,ds:[bx+1] ;第二行颜色属性存入高位 mov es:[si+00a0h],ax ;第二行写入显存地址 mov ah,ds:[bx+2] ;第三行颜色属性存入高位 mov es:[si+0140h],ax ;第三行写入显存地址 inc di ;下一个字符 add si,2 ;显存地址移动 loop s mov ax,4c00h int 21h code ends end start
运行:
assume cs:code, ds:data data segment str db ‘try‘, 0 data ends code segment start: mov ax, data mov ds, ax mov si, offset str mov al, 2 call printStr mov ah, 4ch int 21h printStr: push bx push cx push si push di mov bx, 0b800H mov es, bx mov di, 0 s: mov cl, [si] mov ch, 0 jcxz over mov ch, al mov es:[di], cx inc si add di, 2 jmp s over: pop di pop si pop cx pop bx ret code ends end start
运行结果:
修改后:
子任务2:
修改后代码:
assume cs:code, ds:data data segment x dw 1984 str db 16 dup(0) data ends code segment start: mov ax, data mov ds, ax mov ax, x mov di, offset str call num2str mov si, offset str mov al, 2 call printStr mov ah, 4ch int 21h num2str: push ax push bx push cx push dx mov cx, 0 mov bl, 10 s1: div bl inc cx mov dl, ah push dx mov ah, 0 cmp al, 0 jne s1 s2: pop dx or dl, 30h mov [di], dl inc di loop s2 pop dx pop cx pop bx pop ax ret printStr: push bx push cx push si push di mov bx, 0b800H mov es, bx mov di, 0 s: mov cl, [si] mov ch, 0 jcxz over mov ch, al mov es:[di], cx inc si add di, 2 jmp s over: pop di pop si pop cx pop bx ret code ends end start
运行结果:
修改line3整数结果为2020时:
assume cs:code, ds:data data segment str db 80 dup(?) data ends code segment start: mov ax, data mov ds, ax mov si, 0 s1: mov ah, 1 int 21h mov [si], al cmp al, ‘#‘ je next inc si jmp s1 next: mov cx, si mov si, 0 s2: mov ah, 2 mov dl, [si] int 21h inc si loop s2 mov ah, 4ch int 21h code ends end start
运行结果:
总结对这个简单的c代码反汇编后,你对反汇编出来的汇编指令分析的内容总结。可以包括但不限于以下内容的总结:
参数传递时将值存入寄存器后push入栈,之后通过call命令跳转调用sum函数,通过访问[x]和[y]的实现相加,保存在eax寄存器中。调用函数时,参数从右向左入栈。
原文:https://www.cnblogs.com/litmu/p/14121671.html