Five years after its introduction, it is easy to forget exactly how revolutionary the iPhone was. At that time, there were no smartphones as we know them today. There were phones that made phone calls, and some phones that had web browsers, but these browsers were not full featured. They could render only the most basic of web pages and even then only at very low resolutions. The iPhone changed the game.

Here was a device that was almost entirely screen, had a WebKit-based web browser, and an operating system that you could upgrade yourself without waiting for your carrier to do it for you. Combined with the capability to store photos, play music, and send text messages, it was something people really wanted to have (see Figure 1). At the same time, the iPhone wasn't perfect. The original iPhone had very slow data speeds, no support for third-party applications, and minimal security, but it was mostly responsible for the smartphone and tablet revolution.

Figure 1 A crowd of customers line up to buy the first iPhone. Credit: Mark Kriegsman (


Since the original iPhone came out in 2007, a series of other Apple devices have come along, all now running iOS. Of course back when the original iPhone and some other devices came out, the operating system wasn't called iOS. The original iPhone was identified by Apple as OS X, like its ...

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