The iPad was a planned device for Apple as far back as 2002.
The user interface of each iPad model is built around the device’s multi-touch screen, including a virtual keyboard rather than a physical one. The iPad has Wi-Fi and cellular connectivity. However, only the third and fourth generation iPad models include 4G capability. All iPad models except the iPad mini include a 9.7-inch display. The iPad mini’s display is the only one to have dropped the larger display in favor of a smaller 7.9-inch display. The first, second, and fifth generation iPads featured a pixel density of 1,024 x 768 pixels while the third and fourth generation iPad devices feature a sharper 2,048 × 1,536 pixel Retina Display.
The iPad is largely blamed for lower than expected PC sales starting in 2011.
As of 2012, Apple’s App Store offered more than 700,000 apps by Apple and third party developers, though not all of these are optimized for iPad use.