For first of all ,
I don't like something to clould my I/O out while it's still attached to my case of PC .
Some pay for VB? and you 'll get your I/O back.
NO!!!

I used to install Masm+Turbo C ,it asked for target operating system. That 's the way on accessing H/W.

I don't know how NT scheduling to pre-empt out h/w critical time and don't understand how NT treat DOS program.