A touchpad or trackpad is a type of pointing device. Its largest component is a tactile sensor: an electronic device with a flat surface, that detects the motion and position of a user's fingers, and translates them to 2D motion, to control a pointer in a graphical user interface on a computer screen. Touchpads are common on laptop computers, contrasted with desktop computers, where mice are more prevalent. Trackpads are sometimes used on desktops, where desk space is scarce. Because trackpads can be made small, they can be found on personal digital assistants (PDAs) and some portable media players. Wireless touchpads are also available, as detached accessories.