Apple’s new iPad is lighter, thinner, and faster than its predecessors. But its biggest innovation is its ability to run iOS, Apple’s mobile operating system. Unlike most mobile-phone operating systems now on the market, iOS isn’t based on Linux. Instead, it’s written using the programming language called Objective-C.

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Long before the iPhone, other phones had virtual keyboards. Most of them were bad at handling things like URLs and phone numbers. Apple’s virtual keyboard in iPhone 4, in contrast, handles URLs and phone numbers well.
But in some ways, keyboards are harder to get right than screens. The screen is passive; the user just sees it. And in terms of input, keyboards are both text entry and macro recording, two types of tasks that are hard for computers to handle well.

Virtual keyboards had two big problems. First, they were text entry devices. Most people are terrible typists, even good ones. In our training we use a typing benchmark that measures how fast people can type out common phrases. The fastest typists, like Ty Pennington and Nancy Zerg, can type fifty words per minute. But most typists type twenty words per minute or less.

Typically, virtual keyboards made users type slowly, because typing errors were copied to the virtual keyboard. Even worse, they were often so slow that people gave them up entirely.

The second big problem with virtual keyboards was that they were macro recorders. But, unlike the current iPhone keyboard, they were not always efficient at recording. The keyboard might not keep up with fast typists, and typing mistakes were often copied.