数据块间的搬移·汇编程序理解

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sstack segment stack
dw 64 dup(?)
sstack ends

code segment
assume cs:code
start: mov cx,0010H
mov si,3100H
mov di,3200H
cmp si,di
ja a2
;比较si和di寄存器中的数值，若si中的值高于di中的值，则跳转至a2，否则继续执行下面的代码
add si,cx
add di,cx
dec si
dec di
a1: mov al,[si]
mov [di],al
dec si
dec di
dec cx
jne a1
jmp a3
a2: mov al,[si]
mov [di],al
inc si
inc di
dec cx
jne a2
a3: mov ax,4c00H
int 21H
code ends
end start