To:	djgpp AT delorie DOT com
Subject:	Re: pmode selectors
Message-ID:	<19961217.041828.8319.2.aclemmer@juno.com>
References:	<Pine DOT SUN DOT 3 DOT 91 DOT 961216190054 DOT 18715h-100000 AT is>
From:	aclemmer AT juno DOT com (Aaron m Clemmer)
Date:	Mon, 16 Dec 1996 16:20:09 EST

On Mon, 16 Dec 1996 19:03:03 +0200 (IST) Eli Zaretskii
<eliz AT is DOT elta DOT co DOT il> writes:
>The address of __tb is a real-mode seg:off address, that's why it 
>GPFed on you.
	Ok, lets see if I really understand all this.  If a buffer such
as __tb resides in conventional memory, it has a rmode seg:off, so trying
to access it by normal methods (ie *(__tb +1) = 5) will cause a GPF.  So
I should use functions like movedata, which can copy data into conv mem
buffers.
	But if I have a buffer that resides above the first meg, I can
either use a selector to access it, or access it directly?  And if I can
just access it directly, I really wouldn't need to use a selector.  And
doesn't a selector just contain the adress of a buffer, like a pointer?
	And static arrays, dynamic arrays created with malloc(), and
blocks of memory allocated with __dpmi_allocate_memory() all exist above
conv mem, so trying to access these _doesn't_ GPF.
	Wouldn't it be grand if there was a good source of info on
general pmode programming?

>What's wrong with using seg:off way and call dosmemget/dosmemput and 
>all  the other functions discussed in the FAQ?  Why do you at all need
the 
>selector?
	I'd love to, it'd be alot easier... but I'm using some library
that requires I pass it not only the seg:off of a buffer in conventional
mem, but also the selector and pmode offset.  So I passed it the seg:off
using  ((__tb >> 4) & 0xFFFF) for the seg, and (__tb & 0x0F) for the
offset.  I assume that works.  But I still need to pass it __tb's
selector and pmode offset.  But I've yet to find some file or another
that tells you how to get those, or expains them, so that why I asked
here.

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