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From: bobb@vice.ICO.TEK.COM (Bob Beauchaine)
Newsgroups: comp.lang.pascal
Subject: Re: Where's my mouse?
Message-ID: <6257@vice.ICO.TEK.COM>
Date: 7 Nov 90 20:26:05 GMT
References: <13000017@uxh.cso.uiuc.edu>
Organization: Tektronix Inc., Beaverton, Or.
Lines: 29

In article <13000017@uxh.cso.uiuc.edu> mead@uxh.cso.uiuc.edu writes:
>
>I was hoping someone (brighter than I) would know how to (where to)
>directly access the mouse driver (and thus determine it's existance).

  I thought there would be a multitude of appropriate answers to this
  post by now, but this is the method I use.

  (I've lost the original post, so I assume you're using Turbo Pascal).

  The easiest way to determine the existence of a mouse is to check
  interrupt vector $33 (33 hex).  *All* Microsoft compatible mouse
  drivers intercept this vector for compatibility.  

  There are three possibilities for this interrupt vector.  

  1.  The vector itself (i.e., the byte at memory location 0000:0033 
       hex is 0).  Conclusion : no mouse present.

  2.  The byte pointed to by vector $33 is an interrupt return 
      instruction, $CF.  I.e, byte(ptr(0,$33)^) = CF.  
      Conclusion : no mouse present.

  3.  Neither of the above.  Conclusion : a mouse driver is present.

  I have never seen this method fail.

  Bob Beauchaine
  bobb@vice.ICO.TEK.COM