<marquee><h1>Hardware and structure of iPhone</h1></marquee>

The touchscreen is a 9 cm (3.5 in) liquid crystal display (320×480 px at 6.3 px/mm, 160 ppi, HVGA) with scratch-resistant glass, and can render 262,144 colors. The capacitive touchscreen is designed for a bare finger, or multiple fingers for multi-touch sensing. Most gloves and styluses prevent the necessary electrical conductivity. The iPhone 3GS also features a new Fingerprint-resistant oleophobic coating.
The display responds to three sensors. A proximity sensor deactivates the display and touchscreen when the device is brought near the face during a call. This is done to save battery power and to prevent inadvertent inputs from the user's face and ears. An ambient light sensor adjusts the display brightness which in turn saves battery power. A 3-axis accelerometer senses the orientation of the phone and changes the screen accordingly, allowing the user to easily switch between portrait and landscape mode. Photo browsing, web browsing, and music playing support both upright and left or right widescreen orientations. The 3.0 update added landscape support for still other applications, such as email, and introduced shaking the unit as a form of input. The accelerometer can also be used to control third party apps, notably games.
A software update in January 2008 allowed the first generation iPhone to use cell tower and Wi-Fi network locations trilateration. despite lacking GPS hardware. The iPhone 3G and iPhone 3GS employ A-GPS, and the iPhone 3GS also has a digital compass.
The iPhone has three physical switches on the sides: wake/sleep, volume up/down, and ringer on/off. These are made of plastic on the original iPhone and metal on all later models. A single "Home" hardware button below the display brings up the main menu. The touch screen furnishes the remainder of the user interface.
The back of the original iPhone was made of aluminum with a black plastic accent. The iPhone 3G and 3GS feature a full plastic back to increase the strength of the GSM signal. The iPhone 3G is available in black with 8 GB of space, and the discontinued 16 GB model was sold in either black or white. The iPhone 3GS is available in both colors, regardless of storage capacity.