Most computer hardware is not seen by normal users. The hardware of a computer is infrequently changed, in comparison with software and data, which are "soft" in the sense that they are readily created, modified or erased on the computer. 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. Discontinued versions include two generations of the full-sized iPod, all of which had monochrome screens (except for the iPod photo). All three models were released in 2005. 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. 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. The full-sized model stores media on a built-in hard drive, while the smaller iPod nano and iPod shuffle use flash memory. Like many digital audio players, iPods can serve as external data storage devices when connected to a computer. Devices in the iPod family are designed around a central scroll wheel (except for the iPod shuffle) and provide a simple user interface. 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"). The most recent version.