This is a list and comparison of devices designed and marketed by Apple Inc. that run a Unix-like operating system named iOS and iPadOS. The devices include the iPhone, the iPod Touch which, in design, is similar to the iPhone, but has no cellular radio or other cell phone hardware, and the iPad. All three devices function as digital audio and portable media players and Internet clients. The Apple TV, which runs tvOS, is a set-top box for streaming media from local sources and from certain internet services to a connected television set, and has no screen of its own. About 1.35 billion iOS devices have been sold worldwide as of March 2015. As of September 2018, about 2 billion iOS devices have been sold worldwide.