The title says it all, I think.
We know there are universal Turing-machines that only use a binary alphabet. But who proved this first?
Turing himself showed the existence of a universal Turing machine ... but did he also show that such a machine can exist using only a binary alphabet? Or was that someone else?
Or was it just 'obvious' to him and others that this would be the case, and hence no explicit 'first' proof or publication of this result exists?
But if there is a publication that can be considered the 'first' proof of this result, I would be very interested in knowing what that is.
Thank you!
A Turing machine where a tape cell has only two possible symbols is sometimes called a Post machine. Post's model was actually developed independently of Turing's and published later the same year, in 1936; but I think it must have been clear to both of them, and to those who saw both papers, that the two are equivalent.