汇编——多字节有符号加法

在内存中存放两个6字节无符号整数，分别实现加法减法 

方法一：

data segment
x db 12h,34h,23h,45h,34h,56h
y db 11h,11h,11h,11h,11h,11h
sum db 0
data ends

code segment
assume cs:code,ds:data
start:
  mov ax,data
  mov ds,ax      ;操作数据

  lea si,x
  lea di,y
  lea bx,sum
  clc                 ;清楚进位标志的数据

  mov cx,6

again:

  mov al,[si]     ;操作位数是一位 
  adc al,[di]
  mov [bx],al

  pushf            ;压栈防止 影响cf进位
  inc si
  inc di
  inc bx
  popf

  dec cx          ;循环操作指令
  jnz again      ;循环结束
  mov al,0
  adc [bx+1],al    ;实现进位   

  mov ax,4c00h
  int 21h

code ends
end start

 方法二：

data segment
x   dw 1122h
    dw 3344h
    dw 5566h    
y   dw -1111h
    dw -1111h
    dw -1111h 
z   dw 0000h 
    dw 0000h
    dw 0000h
s   dw 0000h
    dw 0000h
    dw 0000h

data ends

code segment
assume cs:code,ds:data
start:
  mov ax,data
  mov ds,ax      
  
  mov ax,[x]
  add ax,[y]
  mov [z],ax
  mov ax,[x+2]
  add ax,[y+2]
  mov [z+2],ax
  mov ax,[x+4]
  add ax,[y+4]
  mov [z+4],ax
  
  mov ax,[x]
  sub ax,[y]
  mov [s],ax
  mov ax,[x+2]
  sub ax,[y+2]
  mov [s+2],ax
  mov ax,[x+4]
  sub ax,[y+4]
  mov [s+4],ax
  
         
  mov ax,4c00h
  int 21h

code ends
end start