Re: Smaller UTM than Rule110

From: Tim Tyler (tim_at_tt1lock.org)
Date: 01/03/05 

Date: Mon, 3 Jan 2005 19:16:04 GMT

Kent Paul Dolan <xanthian@well.com> wrote or quoted:

> Also, by your cited link, _every_ TM _always_ has a
> halt state: any time it has no way to proceed or to
> carry out the current state/symbol pair's command,
> that constitutes a halt state, by the definition
> explicitly given in the material you cited.

Indeed.

With hindsight - it's not how I would have done things:

A TM /already/ has an output stream for communicating with
the rest of the world with. It has no need at all for a
separate independent communication channel down which it
can only ever communicate one bit.

The provision of a second such communications channel pointlessly
complicates the definition of a Turing machine - without any
compensating improvement in its behaviour.

If you remove a Turing machine's halt state you can still
prove all the same theorems using it.

Since one of the main points of a Turing machine is that it
is an abstract model of serial computation, such unnecessary
and superfluous features seem rather undesirable. 

-- 
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