Hi Richard:

It was Thursday May 29 2003. "Win9x and Arachne ?," murmured you to me.

 MP>> So, WinXP will *not* work with a DOS comm/BBS program?  Interesting.
 TP>> That can't be right.

 RT> 'Fraid so

 TP>> One application I look after at work is an ancient Clipper program

 RT> But is it a DOS program?

Yes; Clipper was a 16-bit DOS xBase compiler. It knows nothing of Windows.

 TP>> that sends faxes via a modem attached to a local com port. It runs
 TP>> on an NT4 system, and works fine.

 RT> Does it run in a DOS box?

No other way of running DOS apps under NT that I'm aware of...

 TP>> I suspect - if the first statement above is true - that the OS
 TP>> intercepts calls to the hardware and handles them itself,

 RT> Yes, via a Windows interrupt

Then Windows must hook the DOS interrupt.

 TP>> whether they
 TP>> come from a program running in a DOS box or a Windows app.

 RT> If the application send commands directly to the commport (and thus
 RT> your modem), then it just won't work under WinNT4-style OSs

Tell that to the GPs the system sends faxes to! The fax gateway app is a
Clipper prog, running in a DOS box under WinNT Workstation 4, talking to an
ancient USR Sportster modem attached to Com1.

The main client app - also Clipper - prints to lpt1 fairly successfully,
without (apparently) Windows being aware of it. Shouldn't that work either?
;-)

Bests,

Tim

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