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)