The Apple iPhone 4S was released in October 2011 as an upgrade to the iPhone 4. It features a 3.5-inch Retina display, an A5 chip for improved performance, and an 8-megapixel camera capable of recording 1080p video. The device also introduced the voice assistant, Siri, allowing users to perform tasks using voice commands. The iPhone 4S runs on the iOS operating system, providing access to the App Store for a wide range of applications. It supports both GSM and CDMA networks, making it versatile for different carriers. The phone was well-received for its design and functionality, solidifying Apple's position in the smartphone market.