Although modern PCs are tied to their keyboards, touch-screen technology takes the place of a keyboard and mouse for smartphones and a host of other devices. To sense the position of your fingertips, the touch screen employs a digitizer, a component that turns the screen into a set of coordinates on a grid. The digitizer tracks the movement of your fingers in real time, to control actions such as tapping out a text message, shooting a target in a game or bringing up the latest weather report.
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Form and Location
Typically, a touch-screen digitizer is one piece in a multilayered "sandwich." In modern devices, the screen that produces the images is found at the bottom layer; the digitizer is a transparent sheet that occupies a middle layer on top of the screen, and a thin sheet of hard, protective glass forms the top layer.
The digitizer layer contains a set of microscopically small sensors arranged in regular rows and columns all over its surface. Touching the screen triggers sensors immediately under your fingertip; a specialized electronic circuit receives signals from these sensors and converts them into a specific location on the screen as X and Y coordinates. The circuit sends the location to software that interprets the touch and location according to the app you're using. For example, when you dial a phone number, your fingers touch the numbers on a virtual keypad on the phone's screen. The software compares the locations touched against the keypad and generates a phone number one digit at a time.
Devices that use touch-screen technology include smartphones and tablet computers. Because they don't require a dedicated keyboard, the usable screen size is maximized without compromising any capabilities. Graphics tablets used by artists and industrial designers also employ digitizers, as do ATMs and information kiosks. Because traditional keyboards and mice can be vulnerable in dusty or dirty environments, some industrial machines use touch screens for monitoring and control.
In recent years, an improved digitizer system called multitouch has brought more convenience to smartphones and other mobile devices. Multitouch tracks two or more fingers on the screen at the same time, allowing sophisticated gestures such as shrinking a picture by pinching it.