Apple's iOS 8 goes live Sept. 17, two days before the company's new phones go on sale, Apple announced at its launch event Wednesday in Cupertino, Calif.

The software is available for download for the iPhone 4 and above. First introduced at WWDC, Apple's developer conference in San Francisco in June, iOS 8 marks the second major release of Apple's mobile operating system under the guidance of head designer Jony Ive and new software head Craig Federighi. Apple CEO Tim Cook fired the prior iOS chief, Scott Forstall, in October 2012, in part for refusing to take responsibility for Apple's Maps fiasco. Ive spearheaded a complete redesign of iOS 7, the first major overhaul since Apple introduced the software with the first iPhone in 2007.

Tuesday's event, taking place at the Flint Performing Arts Center in Apple's hometown of Cupertino is one of the most anticipated product launches of the year. Consumers, analysts and investors have been waiting for Apple to introduce the "amazing" new products that CEO Tim Cook has been promising for more than a year. Cook, who took over as CEO from Steve Jobs three years ago, hasn't yet taken the company into new markets beyond those established by his former boss. But he's now expected to do just that with wearables, mobile payments and other possible arenas. iOS 8 is expected to compliment the new hardware.

While iOS 7 featured different typography and color schemes from previous versions of the operating system, along with a flatter design concept, and added features like automatic updates, AirDrop and iTunes Radio, iOS 8 takes Ive's design efforts a step further.

The operating system focuses more on functionality than visuals. With iOS 8, Apple is bringing a laundry list of features that many have desired for years. Most importantly, the new software tackles long-standing issues with iOS' notification system; its tie-ins with Apple's desktop OS X software and with iCloud, software for managing files and devices; and its native SMS client Messages. And it also manages to extend Apple's reach into the health and home-automation space with a suite of new "Kit" apps and developer tools.