Lot's of people know about Turing Machines and the Lambda Calculus and that they both can express any computable function, but often don't really understand what that means. An Unlimited Register Machine is a simple model of a computer, still quite idealised, that is turing equivalent also.

The philosopher Dan Dennett, in his recent book Intuition Pumps and Other Tools For Thinking, devotes a rather large section to URMs titled The Seven Secrets Of Computing Power Revealed.

I will demo a DSL, that is an interesting use of higher order functions, for a kind of URM . The hope is that by simulating the simplest possible register machine and building up complex algorithms you can understand what it means to compute, how a computer works and along the way we will prove the undecidability of the Halting Problem.

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### Unlimited Register Machines

##### Tom Hall

Doing a mixture of Dev and Ops that might be called DevOps. Tom is a mathematician, theatre fan, occasional mountaineer, part time runner, thoroughly nice chap and available in fine bookstores everywhere.