int21 testing

Jukka Heinonen jhei at
Wed May 21 14:51:33 CDT 2003

Ferenc Wagner wrote:
> In VxDCall_VWin32 I can see int31 and int41 dispatch, but no
> trace of int21.  Am I looking at the wrong place?

Well, you should be able to call int21 directly under
Windows 95 using VxDCall (and VWIN32 VxD). It is possible
Wine does not support this because it is unlikely
that user programs really use it (lots of viruses do).
However, fixing this should be quite simple.

I was thinking more about using DeviceIoControl 
(see DeviceIo_VWin32) which seems to allow calling int21 
under Wine and which is much easier to use than VxDCall. 
However, it looks like this does not work under Windows. 
At least all the information I have found about this say
that DeviceIoControl can only be used to call a limited set
of int21 functionality.

Jukka Heinonen <>

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