I think you're misunderstanding the table.  Starting at address 0040:0000
(or 0000:0400 if you want to segment it differently) you will find a table.
As Bob Ammerman pointed out (I forgot to) you can only access the hardware
directly from DOS, Windows 3x and 9x; it won't work under NT/2000; don't
know about ME.
Here is an example of what you will find, starting at address 0040:0000

0040:0000 F8 03 F8 02 E8 03 E8 02
0040:0008 BC 03 78 03 78 02 XX XX

meaning of course that COM1's I/O addresses start at 03F8, COM2's I/O
addresses start at 02F8, and so on.  When DOS, etc, boot up, they scan a
known set of addresses for the ports.  When they find the hardware the stick
the address in the table.  We had a project where we had to put a COM port
at a non-standard address (DOS couldn't find it on its own).  This was on a
little PC/104 i386EX processor with DOS and there were issues with com
ports, a long story.  Anyway, as part of our initialization we had to stick
our own address into the table.  Pretty simple.

----- Original Message -----
From: "dr. Imre Bartfai" <root@PROF.PMMF.HU>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Saturday, March 31, 2001 6:42 AM
Subject: Re: [OT]: Com port base address


> Correct. However, 0000 is not a valid address, rather means "port does not
> exist".
> Regards,
> Imre
>
> On Fri, 30 Mar 2001, John Pfaff wrote:
>
> > Under DOS and Windows the addresses are stored in the BIOS data area as
> > follows:
> >
> > 0040:0000 COM1 Port Address
> > 0040:0002 COM2 Port Address
> > 0040:0004 COM3 Port Address
> > 0040:0006 COM4 Port Address
> > 0040:0008 LPT1 Port Address
> > 0040:000A LPT2 Port Address
> > 0040:000C LPT3 Port Address
> >
> > - John
> >
> > ----- Original Message -----
> > From: "David Duffy" <piclist@AUDIOVISUALDEVICES.COM.AU>
> > To: <PICLIST@MITVMA.MIT.EDU>
> > Sent: Thursday, March 29, 2001 6:05 PM
> > Subject: Re: [OT]: Com port base address
> >
> >
> > > David Stubbs wrote:
> > > >Hey,
> > > >
> > > >Does anyone know of a way I can find out the base address of the
> > different
> > > >com ports in my program I am making under Windows. Thank for your
help.
> > >
> > > com1            Hex 3F8
> > > com2            Hex 2F8
> > > com3            Hex 3E8 (?)
> > > com4            Hex 2E8 (?)
> > > Unlike LPT ports, com ports have fixed base addresses.
> > > Regards...
> > >
> > > --
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