This program provides a TTerminalWindow object derived from TWindow.
The interior of this object is derived TTerminal. Such an object offers
a handy way of adding text to the end of a scroller and navigating
(using cursor keys or mouse) around the scroller.

We also derive a new application object from TApplication called
TComApp. The actual application, TMyApp is then derived from TComApp.
In your programs, you might want to consolidate TComApp and TMyApp
into one object.
We broke it into two objects in case you wanted to move TComApp and
TTerminalWindow objects into their own units.

Serial port output is handled by TTerminalWindow's interior. Whenever
it receives a evKeyDown message it sends that character to the serial
port with PutChar.

Serial port input is handled by TComApp's Idle method. Each time that
method is called (which is once for every generated message) it checks
the com port for characters waiting in the input buffer. If it finds
that a character is ready, it will retreive that character, format an
event record with a custom event code of evComChar and passes that
event directly to the TTerminalWindow's HandleEvent method. It will
process up to 10 characters each time Idle is called (speeding things
up a bit whenever a large block of characters arrives at the serial
port).

TTerminalWindow's TInterior is the object that actually processes the
evComChar event. To do so, it calls TTerminal's CharWrite method to
add that character to the end of the scroller buffer and display it.

Note this is a rather "bare bones" implementation. The TTerminal
ancestor of TTerminalWindow's interior doesn't have the necessary
methods to easily add terminal emulation (which would need to modify
colors, position the cursor anywhere within the scroller buffer, etc.).
To add emulation, you'll either need to add methods to
TTerminalWindow's interior, or perhaps, choose a different ancestor
than Turbo Vision's TTerminal.

Additionally, this example gives little consideration to performance.
You may want to consider processing characters in blocks rather than
generating an event for each character. That is, the TComApp Idle
method would collect a block of input characters, place a pointer to
that block in the event record's InfoPtr field, and have the
TTerminalWindow's HandleEvent method process that entire block at once.

Released to the public domain

Written by Terry Hughes, TurboPower Software
Version 1.0 - 6-10-91
  initial release

1.01 - 8-24-92 : wasn't releasing comport memory when terminal window 
                 closed
1.02 - 12-5-92 : updated for BP7