iPad 4

The fourth-generation iPad (marketed as iPad with Retina display, colloquially referred to as the iPad 4) is a tablet computer produced and marketed by Apple Inc. Compared to its predecessor, the fourth-generation iPad maintained the Retina Display but featured new and upgraded components such as the Apple A6X chip, and the Lightning connector, which was introduced on September 12, 2012. It shipped with iOS 6.0, which provides a platform for audio-visual media, including electronic books, periodicals, films, music, computer games, presentations and web content.

It was announced at a media conference on October 23, 2012 as the fourth generation of the iPad line, succeeding the third-generationiPad, and was first released on November 2, 2012 in thirty-five countries. The device was released throughout December in ten other countries including China, India and Brazil. The third generation was discontinued following the fourth's announcement.

The device is available with either a black or white front glass panel and various connectivity and storage options. Storage size options include 16 GB, 32 GB, 64 GB, and 128 GB; the available connectivity options are Wi-Fi only and Wi-Fi + Cellular with LTEcapabilities.

The fourth-generation iPad received primarily positive reviews and was praised for its hardware improvements as well as the Retina display, which was also featured in the device's predecessor. Furthermore, benchmarks reveal that the fourth-generation iPad is able to perform CPU-reliant tasks twice as fast as its predecessor. During the first weekend of sales, an aggregated amount of three million fourth-generation iPads and iPad Minis were sold.

Software

The fourth-generation iPad is shipped with iOS 6.0. It can act as a hotspot with some carriers, sharing its Internet connection over Wi-Fi, Bluetooth, or USB,  and also access the Apple App Store, a digital application distribution platform for iOS. The service allows users to browse and download applications from the iTunes Store that were developed with Xcode and the iOS SDK and were published through Apple. From the App Store, GarageBand, iMovie, iPhoto, and the iWork apps (Pages, Keynote, and Numbers) are available.

The iPad comes with several pre-installed applications, including Siri, Safari, Mail, Photos, Video, Music, iTunes, App Store, Maps, Notes, Calendar, Game Center, Photo Booth, and Contacts. Like all iOS devices, the iPad can sync content and other data with a Mac or PC using iTunes, although iOS 5 and later can be managed and backed up without a computer. Although the tablet is not designed to make phone calls over a cellular network, users can use a headset or the built-in speaker and microphone to place phone calls over Wi-Fi or cellular using a VoIP application, such as Skype. The device has a dictation application, using the same voice recognition technology as the iPhone 4S. The user speaks and the iPad types what they say on the screen, though the iPad must have an internet connection available (via Wi-Fi or cellular network) due to the feature's reliance on Apple servers to translate the speech.

The fourth-generation iPad has an optional iBooks application, which displays books and other ePub-format content downloaded from the iBookstore.  Several major book publishers including Penguin Books, HarperCollins, Simon & Schuster, and Macmillanhave committed to publishing books for the device. Despite being a direct competitor to both the Amazon Kindle and Barnes& Noble Nook, both Amazon.com and Barnes & Noble offer e-reader apps for the iPad.

It was announced at the Apple WWDC 2015 that the iPad 4 (along with various other devices) will support iOS 9, which is the latest version of iOS.

Hardware

The device has an Apple A6X SoC which comprises a 32-bit Apple Swift dual-coreCPU running at 1.4 GHz and a quad-core PowerVR SGX554MP4 GPU, 1 GB of RAM.It also features a 5-megapixel, rear-facing camera capable of 1080p video recording; and a 720p HD front-facing videophone camera designed for FaceTime.The device features a 9.7" (diagonal) display with aresolution of 2,048 by 1,536 (QXGA) resulting in 3.1 million pixels, this gives the display a pixel density of 264 ppi. The total number of pixels used in the display of the fourth-generation iPad is four times that of the iPad 2 – providing even scaling from the prior model.

As with all previous generations of iPhone and iPad hardware, there are four buttons and one switch on the fourth-generation iPad. With the device in its portrait orientation, these are: a "home" button on the face of the device under the display that returns the user to the home screen, a wake/sleep button on the top edge of the device, and two buttons on the upper right side of the device performing volume up/down functions, under which is a switch whose function varies according to device settings, generally functioning either to switch the device into or out of silent mode or to lock/unlock the orientation of the screen. Externally, the fourth-generation iPad is identical to its predecessor apart from the differences between dock connectors used and change of manufacturers that produce the display. In addition, the Wi-Fi only version weighs 652 grams while the cellular model weighs 662 grams – 2 grams heavier than their respective predecessors. The display responds to other sensors: an ambient light sensor to adjust screen brightness and a 3-axis accelerometer to sense orientation and switch betweenportrait and landscape modes. Unlike the iPhone and iPod Touch's built-in applications, which work in three orientations (portrait, landscape-left and landscape-right), the iPad's built-in applications support screen rotation in all four orientations, including upside-down. Consequently, the device has no intrinsic "native" orientation; only the relative position of the home button changes.

The tablet is manufactured either with or without the capability to communicate over a cellular network. All models can connect to awireless LAN via Wi-Fi. The fourth-generation iPad is available with 16, 32, 64 or 128 GB of internal flash memory, with no expansion option. Apple sells a "camera connection kit" with an SD card reader, but it can only be used to transfer photos and videos.

The audio playback of the fourth-generation iPad has a frequency response of 20 Hz to 20,000 Hz. Without third-party software it can play the following audio formats: HE-AAC, AAC, Protected AAC, MP3, MP3 VBR, Audible formats (2, 3, 4, AEA, AAX, and AAX+), ALAC, AIFF, and WAV.

This iPad uses an internal rechargeable lithium-ion polymer (LiPo) battery that can hold a charge of 11,560 mAh.The batteries are made in Taiwan by Simplo Technology (60%) and Dynapack International Technology (40%). The iPad is designed to be charged with a relatively high current of 2 amps using the included 12 W USB power adapter and Lightning connector. While it can be charged by an older USB port from a computer, these are limited to 500 milliamps (0.5 amps). As a result, if the iPad is in use while powered by a computer, it may charge very slowly, or not at all. High-power USB ports found in newer computers and accessories provide full charging capabilities. Apple claims that the battery can provide up to 10 hours of video, audio playback, or web surfing on Wi-Fi, 9 hours of web surfing over a cellular connection, or one month on standby. Like any rechargeable battery, the iPad's battery loses capacity over time. However, the iPad's battery is not user-replaceable. In a program similar to iPod and iPhone battery-replacement programs, Apple promised to replace an iPad that does not hold an electrical charge with a refurbished unit for a fee.During the battery replacement process, user data is not preserved/transferred, and repaired or refurbished units come with a new case.The warranty on the refurbished unit may vary between jurisdictions.

Accessories

The Smart Cover, introduced with the iPad 2, is a screen protector that magnetically attaches to the face of the iPad. The cover has three folds which allow it to convert into a stand, which is also held together by magnets. The Smart Cover can also assume other positions by folding it. Smart Covers have a microfiber bottom that cleans the front of the iPad, and wakes up the unit when the cover is removed. It comes in five colors of both polyurethane and the more expensive leather.

Apple offers several other accessories, most of which are adapters for the proprietary Lightning connector, the only port besides the headphone jack. A dock holds the iPad at an angle, and has a dock connector and audio line-out port. The iPad can use Bluetooth keyboards that also work with Macs and PCs. The iPad can be charged by a standalone power adapter ("wall charger") compatible with iPods and iPhones, and a 12 watt charger is included.