## Dave Hudson## hashingit.com |

After 40+ years of writing software and a stint designing CPU instruction sets I finally got around to reading Alan Turing’s 1936 paper on computable numbers.

This has led to me a huge amount of research about Universal Turing Machines (UTMs) and that there are so many different designs. Most interesting are the searches for minimal UTMs (smallest numbers of states, symbols and tapes).

Some interesting pages:

- Implementation of a Turing Machine in Scheme: https://web.mit.edu/manoli/turing/www/turing.html
- Wikipedia: https://en.wikipedia.org/wiki/Universal_Turing_machine
- Small universal Turing machines: http://www.ini.uzh.ch/~tneary/tneary_Thesis.pdf
- Stephen Wolfram’s 2-state, 3-symbol, TM: https://en.wikipedia.org/wiki/Wolfram%27s_2-state_3-symbol_Turing_machine
- Stephen Wolfram’s book, “A New Kind of Science”: https://www.wolframscience.com/nks/

One of the more interesting thoughts for me is the idea of TM’s description number. The idea of a number to describe a particular computation seems quite appealing