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Devices in the iPod family are designed around a central scroll wheel (except for the iPod shuffle) and provide a simple user interface. Most computer hardware is not seen by normal users. The iPod is currently the world's best-selling digital audio player, and its worldwide mainstream adoption makes it one of the most popular consumer brands. The bundled software used for uploading music, photos and videos to the iPod is called iTunes. All three models were released in 2005. Firmware is a special type of software that rarely, if ever, needs to be changed and so is stored on hardware devices such as read-only memory (ROM) where it is not readily changed (and is therefore "firm" rather than just "soft"). As of July 2006, the lineup consists of the 5th generation iPod, with a video player; the iPod nano, with a color screen; and the iPod shuffle. Computer hardware is the physical part of a computer, including the digital circuitry, as distinguished from the computer software that executes within the hardware. As a music jukebox application, iTunes stores a comprehensive library of the user's music on their computer and can play, burn, and rip music from a CD. Like many digital audio players, iPods can serve as external data storage devices when connected to a computer. Discontinued versions include two generations of the full-sized iPod, all of which