An iPhone can function as a video camera (video recording was not a standard feature until the iPhone 3GS was released), a camera phone, a portable media player, and an Internet client with email and web browsing capabilities, can send texts and receive visual voicemail, and has both Wi-Fi and 3G connectivity.
The user interface is built around the device's multi-touch screen, including a virtual keyboard rather than a physical one. Third-party as well as Apple application software is available from the App Store, which launched in mid-2008 and now has over 425,000"apps" approved by Apple. These apps have diverse functions, including games, reference, GPS navigation, social networking, security and advertising for television shows, films, and celebrities.
There are four generations of iPhone models, each accompanied by one of the four major releases of iOS (formerly iPhone OS). The original iPhone was a GSM phone that 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. The iPhone 3GS added a compass, faster processor, and higher resolution camera, including video recording at 480p.
The iPhone 4 has a rear facing camera (720p video) and a front facing camera (at a lower resolution) for FaceTime video calling and for use in other apps like Skype. The phone also featured a higher-resolution display; it was released on June 24, 2010. In the U.S., AT&T was the only authorized carrier until February 10, 2011, when a CDMA version of the iPhone 4 launched for Verizon.
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 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 right. Volume controls are located on the left side of all iPhone models and as a slider in the iPod application.
The iPhone features an internal rechargeable battery. Like an iPod, but unlike most other mobile phones, the battery is not user-replaceable.The iPhone can be charged when connected to a computer for syncing across the included USB to dock connector cable, similar to charging an iPod. Alternatively, a USB to AC adapter (or "wall charger," also included) can be connected to the cable to charge directly from an AC outlet. A number of third-party accessories (car chargers, portable chargers, battery cases, stereo dock chargers, and even solar chargers) are also available
The original iPhone and iPhone 3G feature a built-in Fixed focus 2.0 megapixel camera located on the back for still digital photos. It has no optical zoom, flash or autofocus, and does not support video recording (iPhone 3G does support video recording via third-party App available on the App Store), however jailbreaking allows users to do so. Version 2.0 of iPhone OS introduced the capability to embed location data in the pictures, producing geocoded photographs.
