The nature of operating systems - was: IRQs and interrupt handlers

[kilgallen@eisner.decus.org (Larry Kilgallen)]

In article <6k1rq4$58t@top.mitre.org>, mfb@mbunix.mitre.org (Michael F Brenner) writes:

> But it is a fact that the raw strokes are not available to user
> programs in most newer operating systems.
> 
> Something as simple as which keys are currently being held down,
> the true location of the mouse, or lighting up a pixel on the screen
> are forbidden to the programer, glorifying mediocrity in the name
> of security. The word security is deprecated by this philosophy
> of hiding the raw input-outputs streams from the authorized users.

That view seems particularly tied to the notion of a single-user
computer.  I certainly would not want _you_ to have access to the
bare metal on a machine where my process was running.  (But of
course, you should be willing to tolerate _me_ having such access.:-)

There are several software products (I hesitate to call them
operating systems) available for single-user computers, but when
you start paying for multiprocessing operating systems you find
the market is driven by those who want to minimize the chance
of users interfering with one another.

And yes, if you just want "character-at-a-time-as-soon-as-possible"
you _do_ have the potential to interfere with other users via timing.
Operating systems arbitrate the degree to which such interference is
tolerated, and ideally allow the system manager to vary the degree
to which it is tolerated.

Larry Kilgallen