-=> Quoting Richard Town to Tim Parsons <=-

 -=> Quoting Tim Parsons to Mike Powell <=-
 
 RT>> Win95, Win98, Win98SE, and WinME _will_ allow hardware to be directly
 RT>> manipulated by applications.  It's the WinNT-series of OSs -- WinNT4,
 RT>> WinXP, Win2k series -- that won't
 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?
 
 TP> that sends faxes via a modem attached to a local com port. It runs on
 TP> an NT4 system, and works fine.

 RT> Does it run in a DOS box?
 
 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
 
 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

NT (and OS/2) simply let programs in the DOS box *think* they have a
DOS box to themselves (virtual86 mode on the CPU chip). The OS then
gets to pass on or deny any attempts at direct hardware access. Or for
some types of access it can "filter" the access thru a driver.


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