从SOURCE_BUFFER单元开始存放了20个字母A, 编程将这20个字母A的字符 串向下移10个单元.

从SOURCE_BUFFER单元开始存放了20个字母A, 编程将这20个字母A的字符串向下移10个单元.

data                  segment
source_buffer    db        20 dup('A')
data ends 
extra                 segment 
dest_buffer        db        20 dup( ? )
extra ends 
code segment 
main proc far
         assume cs:code,ds:data,es:extra
start:
         push ds
         sub ax,ax
         push ax
         mov ax,data
         mov ds,ax
         mov ax,extra
         mov es,ax
         lea si,source_buffer
         lea di,source_buffer+10
         cld
         mov cx,20
         rep movsb
         ret
main endp
code ends
        end start