The high-end iPhone preceding the iPhone 6 and a major upgrade from the iPhone 5. Introduced in September 2013 along with the entry-level 5C, it was the first time Apple offered two new phone models (see iPhone 5C). The 5S also featured iOS 7, a completely redesigned OS for the first time since the iPhone's debut in 2007 (see iOS versions). Available with up to 64GB of storage, the 5S employs Apple's A7 64-bit CPU for faster processing and a second processor for motion sensing (see Apple coprocessor). A greatly enhanced camera with a larger sensor provides image stabilization, more accurate flesh tones (see True Tone Flash), slow-motion video, zoomed video, image filters and new modes for square pictures, panoramas and 10 stills per second. The 5S uses a Nano SIM card, rather than the Micro SIM in previous iPhones. Touch ID A significant external change is Touch ID, which adds a fingerprint reader to the home button. Users touch the button to unlock the phone or download from the App store. See iPhone.