Dave,
did the IBM mainframe and early microprocessor model of instruction
pointer; address / data registers map onto a finite-state machine? I
can see how it might be done(e.g. by mapping op codes to microcoded
OR/NAND/SHIFT/JUMP etc.), but I don't see why it /would/ be done that way.
On 19/12/2013 15:39, Dave Crozier wrote:
A finite state machine/system is one that:
a. knows the current status of the "machine" at all times
b. can recognise a state change of the machine
c. reacts to a state change via a predetermined set of rules
d. triggers a change in state for any state change in (c) above
Although this would seem to be how any program/system can be defined, the Finite State
Machine (FSM) is very rigid in how it models the "system". You need very
structured code patterns and usually these are driven via an events table where each
event can have a number of states with events being rows and states being columns.
The table is scanned via the events handler and the combination of row/column
values at any instant in time dictate either a state change or a requirement
for a state change. This state change is then handled, normally in an
alternative programming thread and the results of the change fed back into the
events table.
What happens is that the system becomes virtually dynamic with regards to "consequential
events" as there will be a finite but usually very large number of "states" that
have to be processed or recognised.
Lots of the mainframe operating systems that I used to work on at Singer used
this methodology as did the early microcode mainframes at ICL.
The biggest difficulty in writing software this way is not the programming, it
is actually defining the finite number of events, states and combinations of
the two that will generate a state change that may or may not affect the actual
state of the thread that is currently processing the change.
Hope this makes sense as although it is a simple concept, the implementation of
it is not a trivial task.
Dave
-----Original Message-----
From: ProFox [mailto:[email protected]] On Behalf Of Nicholas Geti
Sent: 19 December 2013 04:35
To: [email protected]
Subject: Finite State Machine
Do any of you know the Finite State Machine technique for programming? Has
anyone used it to do programming?
Nick Geti
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