There are many different approaches to designing robots.
Subsumption architecture is a way of designing robots that are not programmed. A simple robot is designed and then bits are added to the robot to make its behaviour more complex. Rodney Brooks, Director of the Artificial Intelligence Laboratory at the MIT in the USA, first suggested this approach.
The idea of subsumption architecture has been developed into BEAM robots by Mark Tilden who concentrates on analogue electronics to control robots. There are several sites devoted to BEAM robotics: