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. 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. The full-sized model stores media on a built-in hard drive, while the smaller iPod nano and iPod shuffle use flash memory. 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"). Personal computers, the computer hardware familiar to most people, form only a small minority of computers (about 0.2% of all new computers produced in 2003) Market statistics. Discontinued versions include two generations of the full-sized iPod, all of which had monochrome screens (except for the iPod photo). Most computer hardware is not seen by normal users. 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. 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,.