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 
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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.