At the center of the robot block diagram are the controllers. Robots usually have a main controller, a computer of some kind. They may also have some secondary controllers, and some more unusual robots have many controllers. Sticking with the conventional main controller, this is the system that your code will run. It is the part that connects all the other components together and forms the basis of their interactions.
Controllers and IO
IO pins
IO pins are used for input and output from the controller; they give the controller its ability to connect to real-world sensors and motors.
The number of IO pins on the controller can be a major limiting factor in what you can connect to a robot without using secondary controllers...
