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:    • Chomsky Hierarchy - Computerphile  
$5 Computer – Raspberry Pi Zero:    • Raspberry Pi Zero - the $5 Computer -...  
Why Computers Use Binary:    • Why Use Binary? - Computerphile  
Steve Furber on ARM:    • ARM Processor - Sowing the Seeds of S...  
CPU vs GPU:    • CPU vs GPU (What's the Difference?) -...  

Professor Brailsford's Notes: http://bit.ly/computerphile_Chomsky
Professor Brailsford's t-shirt kindly supplied by Peleg Bar Sapir

  / computerphile  
  / computer_phile  

This video was filmed and edited by Sean Riley.

Computer Science at the University of Nottingham: http://bit.ly/nottscomputer

Computerphile is a sister project to Brady Haran's Numberphile. More at http://www.bradyharan.com