An iPhone functions as a camera phone, including text messaging and visual voicemail, a portable media player, and an Internet client, with e-mail, web browsing, andWi-Fi connectivity. The user interface is built around the device's multi-touch screen, including a virtual keyboard rather than a physical one. Third-party applications are available from the App Store, which launched in mid-2008 and now has well over 300,000 "apps" approved by Apple. These apps have diverse functionalities, includinggames, reference, GPS navigation, social networking, security and advertising for television shows, films, and celebrities.
There are four generations of iPhone models, and they were accompanied by four major releases of iOS (formerly iPhone OS). The original iPhone established design precedents like screen size and button placement that have persisted through all models. The iPhone 3G added 3G cellular network capabilities and A-GPS location. TheiPhone 3GS added a compass, faster processor, and higher resolution camera, including video. The iPhone 4 has two cameras for FaceTime video calling and a higher-resolution display. It was released on June 24, 2010.
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 of the iPhone have a resolution of 320 x 480 (HVGA) at 163 ppi, while the display on the iPhone 4has a resolution of 640 x 960 at 326 ppi.
The touch and gesture features of the iPhone are based on technology originally developed by Finger Works. Most gloves and styluses prevent the necessary electrical conductivity; however, capacitive styli can be used with iPhone's finger-touch screen. The iPhone 3GS also features a fingerprint-resistantoleophobic coating.
The top and side of the iPhone 3GS, externally identical to the iPhone 3G. The switches were black plastic on the original model. From left to right, sides: wake/sleep button, SIM card slot, headphone jack, silence switch, volume controls. Top: earpiece, screen.
The iPhone has a minimal hardware user interface, featuring only four or five buttons, depending on whether the volume control is counted as one button or two. 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. Directly above the volume controls is a silence button 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.
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. Unlike the iPad, the iPhone does not rotate the screen when turned upside-down, with the Home button above the screen. 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. The iPhone 4 also includes a gyroscopic sensor, enhancing its perception of how it is moved.
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, 3GS and 4 employ A-GPS, and the iPhone 3GS and 4 also have a digital compass.
Audio and output
One of two speakers (left) and the microphone (right) surround the dock connector on the base of the original iPhone. If a headset is plugged in, sound is played through it instead.
The bottom of the iPhone sports a speaker (left) and a microphone (right) flanking the dock connector. One loudspeaker is located above the screen as an earpiece, and another is located on the left side of the bottom of the unit, opposite a microphone on the bottom-right. The iPhone 4 includes an additional microphone at the top of the unit for noise cancellation, and switches the placement of the microphone and speaker on the base on the unit—the speaker is on the left. Volume controls are located on the left side of all iPhone models and as a slider in the iPod application.
The 3.5 mm TRRS connector for the headphones is located on the top left corner of the device. The headphone socket on the original iPhone is recessed into the casing, making it incompatible with most headsets without the use of an adapter. Subsequent generations eliminated the issue by using a flush-mounted headphone socket. Cars equipped with an auxiliary jack allow for handsfree use of the iPhone while driving as a substitute for Bluetooth.
While the iPhone is compatible with normal headphones, Apple provides a headset with additional functionality. A multipurpose button near the microphone can be used to play or pause music, skip tracks, and answer or end phone calls without touching the iPhone. A small number of third-party headsets specifically designed for the iPhone also include the microphone and control button. The current headsets also provide volume controls, which are only compatible with more recent models. These features are achieved by a fourth ring in the audio jack that carries this extra information.
The built-in Bluetooth 2.x+EDR supports wireless earpieces and headphones, which requires the HSP profile. Stereo audio was added in the 3.0 update for hardware that supports A2DP. While non-sanctioned third-party solutions exist, the iPhone does not officially support the OBEX file transfer protocol. The lack of these profiles prevents iPhone users from exchanging multimedia files, such as pictures, music and videos, with other bluetooth-enabled cell phones.
Composite or component video at up to 576i and stereo audio can be output from the dock connector using an adapter sold by Apple.[43] iPhone 4 also supports 1024x768 VGA output via a dock adapter. The iPhone did not support voice recording until the 3.0 software update.
