Microcontroller
Microcontrollers are robot brains. Microcontrollers allow the designer to interface sensors and specialized control electronics together (along with anything else required for the project) and contain the overall logic of the robot.
The 'general purpose' attribute of a Microcontroller is very significant, and shouldn't be overlooked. A general purpose Microcontroller is a very powerful tool that allows a designer to create a special purpose design. The design becomes partially hardware and partially software. There is great flexibility in the software end, as the designer can create practically unlimited variations on the design by changing the software.
A Microcontroller has several major sections that are pretty typical no matter which type or version of Microcontroller you end up using. Talking about Microcontrollers in the abstract is going to be pretty boring, so I am going to focus this section around the Motorola MC68HC11. I will discuss alternative chips later in the article.