Touchscreens

The touchscreen is the natural evolution of the icon-based operating systems we are used to. Instead of selecting data represented by icons and then issuing commands to manipulate them with a mouse, with touch interfaces there is a direct manipulation of the data through a set of predefined, touch-based actions performed with our fingers on the screen.

Mobile devices can use lots of different methods to detect a person's input on a touchscreen. Many use sensors and circuitry to monitor changes in a specific state. Many monitor changes in electrical current. Others monitor changes in the reflection of sound waves or beams of near-infrared light. Some measure changes in vibration caused when your finger hits the screen's surface, or cameras to monitor changes in light and shadow.

Contemporary devices can process more than one touch at a time. This makes it possible to use multitouch gestures, which we will discuss later in the chapter. Earlier touchscreen devices may...