A Serial Port in an IBM PC or compatible computer is simply a socket 
in the back of the computer into which a cable may be plugged to
connect the computer to a Serial Device.

A Modem is just one example of a Serial Device which may be
connected in this manner. A Microsoft compatible mouse is another
example.

Associated with each port, and uniquely identifying it to the
computer, are two hexadecimal numbers known as IRQ and Base.

Conventionally-used values of these numbers are:

Port 1 - IRQ=4 Base=3F8
Port 2 - IRQ=3 Base=2F8
Port 3 - IRQ=4 Base=3E8
Port 4 - IRQ=3 Base=2E8

Ports 1 and 2 are common to all IBM PCs and compatibles. Ports 3 and 
above may vary.

Within DOS, the expression COM1 is used to denote IRQ=4, Base=3F8;
COM2 is used to denote IRQ=3, Base=2F8.

Please note that these are only conventional NAMES and that, when not
working within DOS, 'IRQ=4, Base=3F8' could be known as COM999 or any
other name.

A computer 'talks to' a Serial Port via its IRQ and Base, not via any
name such as COM1 or COM2.

Scripta allows the user to define up to eight Virtual Ports. They are
known as Virtual Ports because several may be set up pointing to the
same IRQ and Base, and therefore the same 'real' port, but perhaps
varying some way in which the 'real' port is accessed, e.g., using
different baud rates or parity.

By default, Scripta Virtual Ports 1 to 4 are set up with IRQ and Base
as defined above and Virtual Ports 5 to 8 are simply copies of
Virtual Ports 1 to 4.

Therefore, if you configure Virtual Port 1 at 2400 baud and Virtual
Port 5 at 9600 baud, you will have two Virtual Ports (1 and 5), each
pointing at what DOS calls COM1 but automatically adopting different
baud rates when you use them.

As well as changing things like baud rate, Scripta allows you to
change the IRQ and Base associated with any Virtual Port. Therefore,
you could change all eight Virtual Ports to IRQ=3 and Base=3F8,
finishing up with eight Virtual Ports, all pointing at COM1, but
each using different baud rates, or parities, or Flow Control
schemes or having different default upload/download directories or
external protocol drivers.

If you have more than one modem, Scripta allows you to attach them
either to the same port or to different ports, depending on how you
set up the Virtual Ports and on how your hardware is cabled.

Using the command SET PORT=n, Scripta allows you to switch Virtual
Port at any time during the execution of a script.

In the Scripta Dialling Directory, each entry has an associated Port
Number. This is a Virtual Port Number, causing Scripta to use the
port appropriate to each number in the Directory.

As an example of how the average user will set up their ports, let
us suppose that you have one modem connected to what DOS calls COM1.

Without you having to change anything, Scripta already has two
Virtual Ports, 1 and 5, which point to COM1. If all the bulletin
boards and online services that you call have exactly the same
requirements for baud rate, parity, data bits and stop bits then you
need only ever use Virtual Port 1.

However, let us suppose that you mostly call bulletin boards which
require Parity=None, DataBits=8, StopBits=1, but sometimes call an
online service which requires Parity=Even and DataBits=7.

Within Scripta Configuration, you would set the following:

Port 1 - Parity=None
         DataBits=8
         StopBits=1

Port 5 - Parity=Even
         DataBits=7
         StopBits=1

Because you call bulletin boards the most, you would also set
DefaultPort=1. This would cause Scripta always to connect to Virtual
Port number 1 when first entered.

In scripts which call bulletin boards, you need do nothing; in
scripts which call the Even/7/1 online service, you would need to
change to Port 5 at the beginning and back to Port 1 at the end.

e.g., the online service script would have the following form:

Set Port=5
... script commands
Set Port=1

If you want to run your scripts from the Dialling Directory, or
perhaps you prefer to call BBSs manually, without running a script,
then you would need to set the Dialling Directory 'Port' entry to 5
for the Even/7/1 online service and 1 for all other numbers.

If you set up 'ordinary' voice telephone numbers in the Dialling
Directory then it wouldn't matter which Port you used as any may be
used for speech - the Port parameters only specify how data are to
be transmitted.
