Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!watmath!clyde!rutgers!ames!ucbcad!ucbvax!decvax!decwrl!sun!imagen!atari!dyer
From: dyer@atari.UUCP
Newsgroups: comp.sys.atari.st
Subject: Re: Rwabs question
Message-ID: <550@atari.UUCP>
Date: Tue, 3-Feb-87 12:16:03 EST
Article-I.D.: atari.550
Posted: Tue Feb  3 12:16:03 1987
Date-Received: Thu, 5-Feb-87 04:37:37 EST
References: <613@eneevax.UUCP>
Distribution: world
Organization: Atari Corp., Sunnyvale CA
Lines: 38

in article <613@eneevax.UUCP>, iarocci@eneevax.UUCP (Bill Dorsey) says:
>  I wrote a program which intercepts the Rwabs call through the Rwabs
>  vector at 0x476 and noticed something really strange.  It seems that
>  the operating system sometimes calls Rwabs with the buffer argument
>  set to zero.  Does this mean that the operating system will load
>  sectors starting at address zero, writing over all the interrupt
>  vectors stored at these locations?  If, as I suspect, it does not,
>  then what specifically does it do?  In all the documentation I have
>  examined, I have found no mention of Rwabs doing anything special
>  under these circumstances.


From the documentation:

	     LONG Rwabs(rwflag, buf, count, recno, dev)
	     WORD rwflag;
	     LONG buf;
	     WORD count;
	     WORD recno;
	     WORD dev;


          For floppies, if `buf' is NULL, then no  I/O  operation
     is  performed,  and the volume's media-change mode is set to
     `count'.  (This kludge brought to you courtesy  of  the  GEM
     desktop.)

This can be used by applications (such as the desktop), typically
to force a "Might have changed" media change mode on the floppy.
Rwabs() will check for a media change on the next I/O operation.
[DMA cannot occur to location $000000 on the ST since the first
eight bytes are ROM.]

-- 
-Landon Dyer, Atari Corp.	    {sun,lll-lcc,imagen}!atari!dyer

The views expressed here do not not
necessarily reflect those of Atari Corp.	Segments are for worms.