Hi,
With respect to Win XP...
Back when i was writing a serial interface app for reading the serial port,
i used DOS and read the serial port just fine. I believe this classifies it
as a "console app" rather than a "windows app". The code was in
assembler.
When i went to use it as a windows app, it would not read the port but
would give an error as to a program trying to directly access to the port
(or something like that). I was forced to switch to using the Windows
API to access the port from Windows. It worked, but i preferred using
the DOS assembler technique. It's too bad Windows XP screwed that
all up.
The difference then was in the sub system used, DOS or Windows.