Can someone post some code that will read the level of the com port (RS232) lines under MSDOS/Windows? I'm trying to write a small decoder program for an interface that uses only the CTS line of the serial port for it's output, to provide either logic 1 or logic 0.

Jim, Check out this site (you're running DOS, right?) It has code examples, dlls, tutorials and other resources you can use. http://www-cdr.stanford.edu/biomimetics/documents/serial/serial.html

Actually, it sounds to me like you are NOT in DOS, but rather you are trying to use the .NET framework to do this. If that is the case, I have both bad news and good news. The bad news is that MS did not include any .NET framework classes that will do this. You MUST currently use a P/Invoke and utilize the old Win32 code. Simply put you use Interop to dervive a baseclass that can then be used in any language VB, C#, C++, J#, etc. There is a very good example of how to do this at: http://msdn.microsoft.com/msdnmag/issues/02/10/NETSerialComm/ Good Luck!