VB>
  > My situation is: I have a modem card that was developed by
  > our firm themselves. Today I have to make a program for
  > data exchange through it.
VB>

  Does it look like a standard UART to the system ?  If so, then you can
  point COM.SYS (or SIO.SYS) at it, and use it just like any other serial
  device (open, read, write, and close it as a file).  That saves on
  mucking around with IOPL and writing your own device drivers.

  I only suggest this because you did say that it was a "modem card".

  > JdeBP <
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