Processes are startet in the main program and run concurrently.
Each robot behavior may be modeled as a process, with priorities among other processes. Process photo reads the light sensors. If a light source has been recognized, photo will change the robot's course to approach the light. The process evaluates global variables, set by the individual behavior processes. E.g. if bumpers and infra-red sensors are active at the same time, the bumper process gets control over the robot.