Mail Archives: djgpp/2000/03/12/21:30:52

Date: Mon, 13 Mar 2000 06:25:23 +0500
Message-Id: <>
From: Prashant TR <tr AT midpec DOT com>
To: bob tway <tway AT wibble DOT com>
CC: djgpp AT delorie DOT com
In-reply-to: <> (message from bob tway on Sun, 12
Mar 2000 17:31:36 +0000)
Subject: Re: help...
References: <38CBD478 DOT 8F5407ED AT wibble DOT com>
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bob tway <tway AT wibble DOT com> writes:

> i am new to djgpp having used borland 4.51 mostly.can someone explain
> the difference between real and protected mode

There are many differences, one of the important ones being that your programs
will crash less and you get access to 4GB of memory including features such
as virtual memory. The FAQ explains more about it.

> ,and also the difference
> between int86
> and __dpmi_int.

int86 or int386 is used to call protected mode interrupts. __dpmi_int is
the equivalent of the int86 call in Borland.

> i am trying to learn how to use Vesa to do graphics
> stuff,but am having trouble mapping the linear frame buffer.Could
> someone explain exactly what mapping does and how to do it?

Usually when you attempt to access the VESA video memory, the DPMI prevents
you from doing so. This is a protection mechanism. However, you can override
that using the __djgpp_map_physical_memory. The FAQ again has another section
that tells you how to do this. Please go through that and if you still have
more questions, post here again.

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