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Posted: **Thu Jan 15, 2004 3:22 am**

according to listing file generated by nasm the op code for instruction

mov [120h],bx

is

Code: Select all

891E2001

89 is for moving r16 to r/m16 (r is register and m is memory)

2001 is memory location

can you please give description of middle byte 1E

Posted: **Thu Jan 15, 2004 5:54 am**

It's a mod/rm byte. In the case of 1E, it specifies a reg of bx and an r/m of [offs16].

Now do me a favor and hit up Intel's website for the pdfs of the Pentium manuals? They cover this sort of stuff in far more detail than I'm prepared to.

OSDev.org

op code explaination required

op code explaination required

Re:op code explaination required