[Gllug] Sun hardware/firewall memory

[Robert Newson]

t.clarke wrote:

> With regard to the definition of 'multi-tasking', I always thought it was
> defined as being able to do the ironing / talk on the telephone, etc
> at the same time  :-)

By that definition any single processor machine can't multi-task - it can 
only do one task at a time!  (But it is designed to switch between doing the 
tasks, so that it spends a little on one, a little on the next and so on 
until it gets back to doing the first, and if there aren't too many jobs, 
the first one never realises it hasn't been running the whole time (eg 
Ironing, taking notes from a phone call, making scrambled eggs on toast all 
at the same time without burning the toast (no pop-up toaster, have to use 
cooker grill) and letting the eggs get soggy).

AFAIK, there are basically 2 types of multi-tasking: pre-emeptive and 
co-operative.  I think (in basic terms), in prememptive, the system 
interrupts the task after a given time slice and then uses a scheduling 
scheme to decide which task gets the next time slice (2 main versions of 
that: highest accumulated priority and round-robin); whereas in cooperative 
the system gives control over to a task and its upto that task to relinquish 
control back to the system which will then decide which task to [continue 
to] run.

The biggest problem with co-operative is that a task can hog the processor 
and/or if it crashes the system could go belly up.

AFAIK, *nix uses pre-emptive whereas Windows uses co-operative.

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