>>>Can VFP call 'C' functions from the library?
>>>If yes, how do I go about setting the environment
>>>and calling it? (eg. INCLUDE stdio.h , etc)
>>
>>Yes. You have to use DECLARE command form 32-bit DLLs, or FOXTOOLS.FLL, RegFn,CallFn for 16-bit DLLs.
>>You can include any file into form (click form/include file menu in form designer), but it's more reliable to open this file in text editor, check needed variables=values (which you are going to pass calling a function), and use real values instead of these variables.
>
>I have the same problem.Could you suggest some reference books for me about this topic?I want to access the modem for data transmission but I don't know how to do that.Should I use VC++ to do the low level hardware control?How can I do that?

If you want to use standard Windows DLLs you could use some MS Windows API manuals (I actually use VB manual). For specific purposes it might be good to buy some third-party OCX (I believe MS Site should contain a list of such vendors/utilities). BTW for modem transmission you could use Crescent PDQComm OCX (Progress Software Corp. 617-280-3000).