Touch Screen

• The iPad's touch screen works on a capacitive principle: It senses your body's natural electrical capacitance when your finger makes contact with the screen's surface. A fine grid of capacitive sensors called a digitizer sits behind the glass, so when they sense a touch, the digitizer locates where your finger made contact and relays that information to the iPad's main processor chip.
  
  

Multitouch

• As with Apple iPhone and iPod Touch handhelds, the iPad's screen distinguishes the presence of multiple fingertips at the same time. In the case of the iPad, the screen detects up to 11 separate contact points. The digitizer tracks these points and the processor follows their motions in real time, letting the user control the iPad with multiple-touch gestures.
  
  

Structure

• Apple builds the iPad in layers. The digitizer and glass surface faces the user. Behind it lies the liquid crystal display and light emitting diode backlight. The electronic circuit boards and batteries lie between the back cover and the LCD display. Nothing comes between the digitizer and the user; this maintains the touch sensor's sensitivity.
  
  

Gestures

• The iPad supports gestures, or sweeping movements of fingers on the touch screen, to control the various software features. You can enlarge text on a Web browser, for example, by touching the screen with two fingers and spreading them apart. Pinching the fingers together shrinks the text. You scroll a text window down by stroking a single finger from the bottom of the display towards the top. A sideways stroke causes a software application to advance to different screens.
  
  

Keyboard

• The iOS software that comes with the iPad has a virtual typewriter keyboard you use to enter text information in notes, Web pages and other documents. The keyboard sizes itself to about the lower half of the iPad's screen, so the individual key buttons are roughly the size of those on a netbook-type computer. Because the keyboard is virtual and not physical, you get no tactile feedback other than touching the screen; however, the keys turn darker when touched, and the speaker makes a typewriter "click" sound.