The use of I/O functions in Windows programs is still a grey area for most programmers. In this article, we shed some light on the use of the PC’s RS 232 ports in a Windows compatible way.When you wish to use certain devices within a computer, you’ll need routines that control them. With older home computers and PCs, writing such a routine was fairly simple. There was only ever one program running at a time so you didn’t have to take into account that other programs could access the same device. A well-written program would also make sure that the device was set back to its default state at the end of the program’s execution.