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The full-sized model stores media on a built-in hard drive, while the smaller iPod nano and iPod shuffle use flash memory. 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 iPod mini and four generations of the full-sized iPod, all of which had monochrome screens (except for the iPod photo). 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. 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"). It is in embedded systems in automobiles, microwave ovens, electrocardiograph machines,