Despite rumors of a radically redesigned iPhone 5, Apple chose to debut the iPhone 4S with the same design characteristics of its predecessor, the iPhone 4.
The most talked-about feature of the iPhone 4S is Siri, a "digital assistant" that responds vocally to spoken questions such as, "What's the weather like in Los Angeles tomorrow?"
Apple also included an 8-megapixel camera as part of the iPhone 4S hardware package.
The Notifications app consolidates the user's communications into a single interface.
Apple's answer to BlackBerry Messenger, the iMessage app allows iOS 5 users to send unlimited messages to each other.
Apple has deeply baked Twitter into the iOS 5 user interface, allowing users to Tweet directly from Safari, the camera, maps and other features.
Apple's iCloud service, launching as part of iOS 5, stores Apple users' content and shares it between their devices.
Apple's proprietary A5 chip represents a processor upgrade for the iPhone franchise.
The iPhone 4S records video in 1080p, with a built-in editing function.
The iPhone 4S also retains iPhone 4 features such as the high-resolution Retina display.