Date:	Sun, 28 Mar 1999 15:27:23 +0200 (IST)
From:	Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
X-Sender:	eliz AT is
To:	thriller <thriller AT 263 DOT net>
cc:	djgpp AT delorie DOT com
Subject:	Re: questions on protected mode&ISR
In-Reply-To:	<000001be78d9$e3b85f60$dd0d63ca@bj-cmbc>
Message-ID:	<Pine.SUN.3.91.990328152706.22925m-100000@is>
MIME-Version:	1.0
Reply-To:	djgpp AT delorie DOT com
X-Mailing-List:	djgpp AT delorie DOT com
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On Fri, 26 Mar 1999, thriller wrote:

> i'm not familiar with protected mode.and i feel quit terrible in this =
> mode.in djgpp ISR programming i have to lock code.but since Dos is only =
> accessable for 1 time, why i don't need to lock non-ISR codes?

Because non-ISR code can never be executing in the middle of a DOS
call.  In contrast, an ISR can be called while some DOS code is
executing, because hardware interrupts are asynchronous events and may
happen any time.

> and in Borland C++ real mode ISR, i needn't either.

The locking is required in any environment that supports virtual
memory, whereby portions of the address space can be swapped out to
disk.  Borland's real-mode code doesn't support virtual memory, so it
doesn't need to be locked.

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