Date: Mon, 23 May 1994 09:34:41 -0400 (EDT)
From: Task <CROBINSO AT VAXC DOT STEVENS-TECH DOT EDU>
Subject: Interrupts - Real/Protected modes?
To: djgpp AT sun DOT soe DOT clarkson DOT edu

I'm fairly new to DJGPP and to the whole concept of protected mode 
programming in general.  I've been trying to write a program that uses 
a network interrupt that needs a pointer in DS:DX.  I believe I've 
figured out how to take care of that, but I'm still unclear on what 
happens when I call an interrupt in DJGPP.  When I use 
_go32_dpmi_simulate_int() is the system still in protected mode when 
it calls the interrupt?  I have no idea whether this has any effect or 
not, but I managed to get INT 21h vector 09h to work correctly 
(display a string pointed to by DS:DX) and used the same method to 
point to the data block for the interrupt, but when I set the same 
thing up under something like Borland (real mode) it works and under 
DJGPP it either hangs or returns incorrect info.

Is this a real/protected mode problem?  What is going on when an 
interrupt is called?  (IE, does DJGPP switch the system back to real 
mode for the INT?)

Chad