Iphone Screen and input

The touchscreen is a 9 cm (3.5 in) liquid crystal display with scratch-resistant

glass. The capacitive touchscreen is designed for a bare finger, or multiple fingers

for multi-touch sensing. The screens on the first three generations have a resolution

of 320 × 480 (HVGA) at 163 ppi, while that of iPhone 4 has a resolution of 640 × 960 at 326 ppi.

The touch and gesture features of the iPhone are based on technology originally

developed by FingerWorks. Most gloves and styluses prevent the necessary

electrical conductivity; however, capacitive styli can be used with iPhone's

finger-touch screen. The iPhone 3GS and later also feature a fingerprint-resistant

oleophobic coating.

The iPhone has a minimal hardware user interface, featuring only four or five

buttons, depending on the generation. The only physical menu button is situated

directly below the display, and is called the "Home button" because it closes the

active app and navigates to the home screen of the interface. The home button is

denoted not by a house, as on many other similar devices, but a rounded square,

reminiscent of the shape of icons on the home screen. A multifunction sleep/wake

button is located on the top of the device. It serves as the unit's power button,

and also controls phone calls. When a call is received, pressing the sleep/wake

button once silences the ringtone, and when pressed twice transfers the call to

voicemail. Situated on the left spine are the volume adjustment controls. The

iPhone 4 has two separate circular buttons to increase and decrease the volume;

all earlier models house two switches under a single plastic panel, known as a

rocker switch, which could reasonably be counted as either one or two buttons.

Directly above the volume controls is a silence switch that mutes all sound when

engaged. All buttons except Home were made of plastic on the original iPhone and

metal on all later models. The touchscreen furnishes the remainder of the user

interface.