iPhone 4

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 x 480 (HVGA) at 163 ppi, while that of iPhone 4 has a resolution of 640 x 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.

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