They're called 'Finite State Automata" and occupy the centre of Chomsky's Hierarchy - Professor Brailsford explains the ultimate single purpose computer. Note: Professor Brailsford omitted the transition from the 5 state to 25 state by means of a 20p, he has amended the linked notes! Chomsky's Hierarchy: $5 Computer – Raspberry Pi Zero: Why Computers Use Binary: Steve Furber on ARM: CPU vs GPU: Professor Brailsford's Notes: Professor Brailsford's t-shirt kindly supplied by Peleg Bar Sapir This video was filmed and edited by Sean Riley. Computer Science at the University of Nottingham: Computerphile is a sister project to Brady Haran's Numberphile. More at