Applications

• Being able to run third-party software is a major aspect of the iPhone's design. This includes games and software applications designed specifically for the iPhone, and as of July 2011 there are more than 380,000 games and apps available through the iTunes App Store. This software uses a combination of touch-screen controls, motion sensing, Internet connectivity and GPS location services to control them and provide you with functions not available natively on the iPhone.
  
  

Touch Screen

• The iPhone's primary form of user input is its capacitive touch screen. This is a type of touchscreen technology that doesn't rely on pressure to detect points of contact, but instead uses bioelectrical signals to determine where the screen has been touched. This means the iPhone's touch screen is only sensitive to direct contact with skin, but has the advantage of being able to detect up to 10 simultaneous points of contact at any one time.
  
  

Sensors

• The iPhone is equipped with a combination of different motion sensors that allow you to perform actions simply by moving the handset. An accelerometer is built into the iPhone, which is able to detect linear movements on three axis. This is accompanied by a gyroscopic sensor, which is able to detect angular movements on the same three axis. With the inclusion of a digital compass, this allows the iPhone to detect how far, how fast and in which direction the device has physically moved in three dimensional space. Motion sensing is a key form of user interaction on the iPhone.
  
  

Display

• All models of iPhone feature a 3.5-inch back-lit LCD screen, measured diagonally. However, the iPhone 4 is the first model to introduce Apple's Retina display technology, and features a considerably higher pixel density than previous iPhone hardware. The display has a 960 by 640 pixel resolution, and a contrast ratio of 800:1. According to Apple, this is the maximum resolution the human eye is able to detect on a 3.5-inch display, and any higher resolution would not be perceivable. It is also the basis for the display technology's name.
  
  

Hardware

• The iPhone is powered by Apple's A4 processor chip, which is composed of an ARM Cortex-A8 central processing unit alongside a PowerVR SGX 535 graphics processing unit. Wi-Fi Internet connectivity is built into the iPhone, which can access 802.11 b/g/n network standards. Bluetooth 2.1 and GPS location detection services are also included, along with quad-band cellular connectivity for voice and 3G data connections over the cellphone networks. IPhones are available with 16 or 32GB of internal storage, though all models have 512MB of system memory.