IPhone 4

The iPhone 4 is a model of smartphone that was developed by Apple and released on June 24, 2010. It was announced by Apple CEO Steve Jobs on June 7 at the 2010 Worldwide Developers Conference, superseding the iPhone 3GS.

Background
Like previous models of iPhones, its key features included a native mailing app, a web browser, SMS messages, a phone function, and an iPod player, among other things. The iPhone 4 originally shipped with iOS 4 and could be upgraded up to iOS 7.1.2.

It first came in in 16 and 32 GB versions, in black and for GSM only. On January 11, 2011, Verizon announced that it would be selling a CDMA iPhone 4 on February 10, ending Apple's exclusivity agreement with AT&T. The white version for GSM and CDMA became available on April 28. 2011. Lower cost 8 GB "revision A" models became available on October 4, 2011, unlocked from Apple's website.

Features
iPhone 4 features a new 5 megapixel camera with four element lenses, improved white balance and tap to focus for video. a front 0.3 megapixel camera for FaceTime is included. HD 720p video is included. Retina display gives 4x more pixels than previous generation, 326 ppi at 960x640.

Cameras
The iPhone 4 is the first iPhone model to have dual cameras. The front features a 0.3 megapixel selfie camera. The back has an upgraded 5 megapixel camera with an LED flash and can now record in HD 720p video.

FaceTime
The iPhone 4 adds a new feature to the iPhone line, FaceTime. FaceTime allows a user to make a video call over Wi-Fi connection to another iPhone 4 or later, iPod touch (4th generation) or later, a Mac with a webcam running Mac OS X 10.6.7 or later, or an iPad 2 or later.

Retina display
The display on the iPhone 4 is designed by Apple and manufactured by LG. It features a multi-touch screen with a resolution of 960 x 640 at a pixel density of 326 pixels per inch (ppi). The screen is marketed as a "Retina display", based on the criteria that 300 ppi at 12 inches from the eye is the maximum amount of detail that a normal human retina can distinguish.

"Death grip"
Users experienced what appeared to be a dramatic drop in signal bars when gripping the iPhone 4 across antenna seams on the sides of early iPhone 4 models. Apple engineers discovered that this caused was by the formula that calculated signal strength. This discovery, combined with Steve Jobs' initial reaction in blaming users for how they were holding their phones, was dubbed by the media as "Antennagate".

On July 16, 2010, Steve Jobs held a press conference at the Town Hall at the Apple Campus in Cupertino to announce that the company would provide a free case to all iPhone 4 customers to improve signal bars. He also toured the press through Apple's once-secret wireless lab to show how iPhone models were tested. The version of the iPhone 4 that was introduced in February 2011 through  repositioned the antenna seams to minimize the "death grip" effect. The signal bar display problem was supposedly addressed with the release of iOS 4.2.

Bumper
An iPhone 4 Bumper is a ring of rubber that covers the edges around the iPhone 4. The Bumper is designed to protect the iPhone 4, but has the added effect of insulating the antenna on the sides from contact with the user's hand. A different design was introduced to fit the version of the iPhone 4 which repositioned the antenna seams. This antenna configuration was carried over into the iPhone 4S.



Dock
The iPhone 4 Dock became available in June 2010. It had a pass-through 30-pin dock connector on the back that allowed for charging and syncing over USB 2.0. A 3.5 mm line-out port could be connected to external speakers or an audio system. It also supported speakerphone calls. Though it also fits the iPhone 4S, it does not fit either phone if in a case or a bumper.

Carriers
The iPhone 4 was originally released exclusively to AT&T in the U.S. On January 11, 2011, Verizon announced that they would be selling a CDMA version of the iPhone 4 the following month. They added a 'Mobile Hotspot' feature allowing users to use the iPhone as a wireless hotspot for up to 5 connected devices. They also incorporated a new antenna design which was said to avoid the "death grip" problem. In June 2011, Apple introduced the GSM unlocked iPhone 4 in the US at $649 for the 16 GB model and $749 for the 32 GB model.

Hardware

 * Apple A4 System-On-Chip / Samsung S5L8920 application processor
 * ARM Cortex-A8] 32-bit core processor with ARMv7 and THUMB-2 instruction set
 * 1 GHz (underclocked to 600Mhz to prevent overheating)
 * 256 to 512 MB SDRAM
 * Integrated PowerVR SGX535 GPU
 * Toshiba TH58G6D1DT (NAND flash memory storage)
 * Marvell 88W8686 (Wi-Fi)
 * Broadcom BCM4325 (Bluetooth)
 * 3-axis gyroscope, accelerometer, proximity sensor, and ambient light sensor
 * Infineon X-Gold-608 or 618 (GSM), Qualcomm MDM6600 (CDMA) for phone, messages, and cellular data
 * Infineon Hammmerhead II PMB2525 or Broadcom BCM4750 (GSM), Qualcomm MDM6600 (CDMA) for GPS