[kenko]

"I'm sure you've heard this before, but all you have to do is ask whether you can build a Turing machine in whatever language. If you can do this, then you can compute answers to the same things computed by any other Turing complete language."

But you can't do the same things that you can do in other languages.

Computation is pure.

[throwaway1980]

I have never encountered this distinction between activity and computation before. Assuming that you are okay to define (sequential) computation as transforming an input sequence of 1's and 0's into an output sequence of 1's and 0's, can you give me an example of something that a computer does that is not a computation and explain why?