Subj : Interrupts
To   : Lee Aroner
From : Vitus Jensen
Date : Mon May 21 2001 04:15 pm

Moin Lee!

20.05.2001, Lee Aroner wrote a message to Rachel Veraa:

 NA>> And second, I have MS-PDS 7.1 (QuickBasic), which can build both DOS
 NA>> and OS/2 applications. It works wonderful, except for some reason I
 NA>> can't perform ANY "low level" operations if I want to compile for
 NA>> OS/2 (ie. poking around in memory, calling interrupts, etc). I think
 NA>> there is a way around this in the BC compiler (or possibly the
 NA>> linker?) but does anyone know why?

 RV>> First, OS/2 doesn't use interrupts.  You have to use API calls. 
 RV>> Second, since OS/2 is a multitasking OS, it manages memory much
 RV>> differently than DOS does.

 LA>    Not to niggle the point, but of course OS/2 uses interrupts. Each    
 LA> and every one of those API calls is a wrapper around an interrupt    
 LA> call.

Well, to be exact: OS/2 uses callgates to jump into kernel code.  Callbacks are 
similar to interrupt gates in that they switch priviledge levels and have a 
predefined entry point into the kernel but they additionally copy bytes from 
lower to higher level stacks while swichting (byte count defined in the 
callgate).  Something what a interrupt gate won't do.
It is a common design of OSses to do this switching via a software interrupt 
but OS/2 is different.

Bye,
   Vitus

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 * Origin: Even my cleaning lady won't do Windows. (2:2474/424.1)

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