[TUHS] The birth of the Z3
Mike Markowski
mike.ab3ap at gmail.com
Mon May 14 07:44:27 AEST 2018
On 05/13/2018 05:30 PM, Noel Chiappa wrote:
> > From: Clem Cole
>
> > Their is a open question about the need to support self modifying code
> > too. I personally don't think of that as important as the need for
> > conditional instructions which I do think need to be there before you
> > can really call it a computer.
>
> Here's one way to look at it: with conditional branching, one can always
> write a program to _emulate_ a machine with self-modifying code (if that's
> what floats your boat, computing-wise) - because that's exactly what older,
> simple microcoded machines (which don't, of course, have self-modifying code
> - their programs are in ROM) do.
>
> Noel
Rewording that, as I recall from Computability Theory there are three
statements needed for Turing completeness:
1. S <- 0 S is some var
2. S <- S + 1
3. if S=0 goto L L is some line#
Beyond that everything else is icing on the cake. Kind of like needing
nothing more than a bunch of NAND gates to build a computer,
disregarding practicality...
Mike Markowski
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