This is a list and comparison of devices designed and marketed by Apple Inc. that run a Unix-like operating system named iOS, often colloquially referred to simply as iDevices. The devices include the iPhone multimedia smartphone, the iPod touch handheld PC which, in design, is similar to the iPhone but has no cellular radio and other cell phone hardware, and the iPad tablet computer. All three devices function as digital audio and portable media players and Internet clients. The Apple TV, which ran iOS from the second generation of hardware onwards, 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.