Writing programs to talk with parallel port was pretty easy in old DOS days and in Win95/98 too. We could use Inporb and outportb or _inp() or _Outp functions in our program without any problem if we are running the program on DOS or WIN95/98. But entering to the new era of NT clone operating systems like WIN NT4, WIN2000, WINXP, all this simplicity goes away. Being interested in Parallel port interfacing and programming you might have experienced the problems in writing a program that can talk to parallel port successfully in NT based operating systems. When we are trying to run a program which is written using the conventional software functions like Inporb, outportb, _inp() or _Outp on a WINNT or WIN2000 system, it will show an error message that "The exception privileged instruction occurred in the application at location ....".