What does /dda mean?

Hi
I am using lately a lot the /dda option to get things working on my second screen (Matrox)
Now that I am finally mastering the ATI Eyefinity multi head setup I got

*2x 2048x768 (one DVI, one VGA)
*1x 1920x768 (miniDP)

is “dda” the master head? Like dda 0 is default (where you launch vvvv), dda 1 is the second head and n my case I should launch a /dda 2 if I need a renderer in my third screen?
How do you get the exact numbering of the screen? (maybe just what the “Identify” button shows?)

tx
S.<

yeah, elaboration on dda would be nice :)

Hi
got warnings form w7 about Win32/Cmdow being a virus but I see it is a utility to hide the cmd tool to execute bat files, just what I am doing lately with /dda option etc.
???

ahois,

i tried a better definition here: commandline parameters#dda x
hope that helps.