db and dw commands

Greg Frey (gregf@unixg.ubc.ca) Sun, 10 Dec 2000 17:48:10 -0800 

From: "Greg Frey" <gregf@unixg.ubc.ca>
Subject: db and dw commands
Date: Sun, 10 Dec 2000 17:48:10 -0800




Could anyone please clear up for me the syntax for the "db" and "dw"
commmands.

At the end of the Interrupts lecture, the example ISR defines storage using:
tempax    dw    ?
tempds    dw    ?
This seems very clear that we are setting aside 2 bytes with uninitialized
contents for each label.

But, in the Assembly Language lecture, there is an example of creating a
buffer.
buf     db    128    dup (?)
This isn't as clear for me. Does "dup" duplicate whatever is in the
parenthesis 128 times?
In this case, we'll just have 128 uninitialized bytes?

Also, how do we properly access these referenced locations?
mov     ax,buf
mov     ax, [buf]
Would these both do the same thing?

Thanks.

------------------------------------------------------
Greg Frey
gregf@unixg.ubc.ca