Screen and input of the iphone

The 9 cm (3.5 in) liquid crystal display (320×480 px at 6.3 px/mm, 160 ppi) HVGA touchscreen with scratch-resistant glass[26] is specifically created for use with a finger, or multiple fingers for multi-touch sensing. Because the screen is a capacitive touchscreen, bare skin is required. Most gloves or a stylus prevent the necessary electrical conductivity. The screen is also capable of rendering up to 262,144 colors.[29][30][31][32]

The display responds to three sensors. A proximity sensor shuts off the display and touchscreen when the iPhone 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.[33] Photo browsing, web browsing, and music playing support both upright and left or right widescreen orientations.[34] Later, a software update allowed the first generation iPhone to use cell towers and Wi-Fi networks for location finding despite lacking a hardware GPS. The iPhone 3G supplements those methods with A-GPS.

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 the iPhone 3G. 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 brushed metal with a black plastic accent. The iPhone 3G features a full plastic back to increase GSM signal strength.[35] The plastic is black for the 8 GB model, but the 16 GB version is also available in white.