
History
iPod is a brand of portable media players designed and marketed by Apple Inc and launched on October 23, 2001. As of 2008, the current product line-up includes the hard drive-based iPod classic, the touchscreen iPod touch, the video-capable iPod nano and the screenless iPod shuffle and the newly released iPhone. Former products include the compact iPod mini and the spin-off iPod photo (since re-integrated into the main iPod classic line). iPod classic models store media on an internal hard drive, while all other models use flash memory to enable their smaller size (the discontinued mini used a Microdrive miniature hard drive). As with many other digital music players, iPods, excluding the iPod touch, can also serve as external data storage devices. Storage capacity varies by model.
Timeline of iPod models

User interface
iPods with color displays use anti-aliased graphics and text, with sliding animations. All iPods (except shuffle and touch) have five buttons and the later generations have the buttons integrated into the click wheel — an innovation that gives an uncluttered, minimalist interface. The buttons perform basic functions such as play, next track, etc. Other operations such as scrolling through menu items and controlling the volume are performed by using the click wheel in a rotational manner. iPod shuffle does not have a click wheel and instead has five buttons positioned differently from the larger models. iPod touch uses no buttons for any of these functions, instead relying on a Multi-touch input style similar to that of the iPhone.

