8086 op-code need help

Thread Starter


Joined Aug 2, 2009
Hi guys, just wanna ask for confirmation on below op-code.

ADD Bx,1234.

"ADD immed to reg/mem 100000sw mod000r/m [addr] data"

then 1000 0001[SW] 11[mod] 011[BX] 110 [direct address]

opcode = 81 DE H

Is is correct?

How about MOV [1234],AX?


Joined Aug 16, 2011
It has been a while since I used 8086, but here goes.
Your explanation looks right.

MOV [1234],AX means that the value in AX will be moved to the memory address 1234.

Do you have a method of single stepping your code. I used a program SYMDEB years ago which would show you what you are asking about.