Locator devices provide position information to computers and include joysticks, mice, and tablets. Joysticks have levers that control potentiometers to indicate position, mice enable image editing and selection, and tablets sense the position of a stylus on a flat surface. Selector devices are used to select graphical objects and include keyboards, light pens, touch panels, scanners, and track balls. Keyboards input non-graphic data and have cursor keys, light pens allow drawing and pointing, and track balls are used for accurate drawing in CAD workstations.