can have as many as 16 buttons. A pen (also called a stylus) looks like a simple ballpoint pen but uses an electronic head instead of ink. The tablet contains electronics that enable it to detect movement of the cursor or pen and translate the movements into digital signals that it sends to the computer." This is different from a mouse because each point on the tablet represents a point on the screen. Stylus A stylus is a small pen-shaped instrument that is used to input commands to a computer screen, mobile device or graphics tablet. The stylus is the primary input device for personal digital assistants, smartphones and some handheld gaming systems such as the Nintendo DS that require accurate input, although devices featuring multi-touch finger-input with capacitive touchscreens have become more popular than stylus-driven devices in the smartphone market. Touchpad A touchpad or trackpad is a flat surface that can detect finger contact. It is a stationary pointing device, commonly used on laptop computers. At least one physical button normally comes with the touchpad, but the user can also generate a mouse click by tapping on the pad. Advanced features include pressure sensitivity and special gestures such as scrolling by moving one's finger along an edge. It uses a two-layer grid of electrodes to measure finger movement: one layer has vertical electrode strips that handle vertical movement, and the other layer has horizontal electrode strips to handle horizontal movements. Touchscreen A touchscreen is a device embedded into the screen of the TV monitor, or system LCD monitor screens of laptop computers. Users interact with the device by physically pressing items shown on the screen, either with their fingers or some helping tool. Several technologies can be used to detect touch. Resistive and capacitive touchscreens have conductive materials embedded in the glass and detect the position of the touch by measuring changes in electric current. Infrared controllers project a grid of infrared beams inserted into the frame surrounding the monitor screen itself, and detect where an object intercepts the beams. Modern touchscreens could be used in conjunction with stylus pointing devices, while those powered by infrared do not require physical touch, but just recognize the movement of hand and fingers in some minimum range distance from the real screen. Touchscreens became popular with the introduction of palmtop computers like those sold by the Palm, Inc. hardware manufacturer, some high