Greg_d._Moore@mts.rpi.edu (Commander Krugannal) (06/02/90)
The question has come up concerning how Windows can handle
com programs in the background.
There were several answers given (sorry I can't reprint them,
this system doesn't have an adequate mail system). Only one
is close.
The person suggested that the input from the comm port was
buffered and then sent to the com program when it was ready. The
obvious question was WHAT buffers the port.
Well, the obvious answer is Windows itself. All input and output
to programs in Windows is done via messages. Windows monitors
the keyboard, mouse, com ports, and other devices. When it gets
something, it sends the appropriate message to a window function
routine. Windows takes the asynch input (or synch in some cases)
and synchs it for the programs.
So, Windows queues up the com port characters, and at the a
appropriate time sends a message to the comm program and then sends
the characters.
Greg_d._Moore@mts.rpi.edu