The iPod has changed shape and form since the first one was released in 2001. Apple uses the term "generation" to help define the product over time. The 6th generation iPod Classic was released in September 2007. An updated version, commonly referred to as the 7th generation, was released a year later.
Since Apple introduced other models such as the Touch and Nano, the iPod Classic has become increasingly distinct in its layout. The 6th and 7th generation models carry on the legacy of the original click-wheel design with a few changes. These were the first models to come in silver or black and were made of lightweight metal rather than plastic. Though the two look nearly identical, the information inscribed on the back, such as hard drive size, serial number and the year of manufacture, is different.
Later iPod models typically have better hardware performance than the previous versions. A main area of interest is battery life, or how long the device can perform under a full charge. When the 6th generation iPod Classic was released, the battery had a base life of 30 hours of audio play. The 7th generation model had an improved base life of 36 hours.
The 6th generation iPod was offered in both 80GB and 160GB hard drive capacity models, at the time Apple's largest capacity ever. The 7th generation iPod was initially available with only a 120GB hard drive, but soon thereafter, was changed to 160GB.
Initially, iPods were as expensive as a basic computer. As the product became more popular, the Classic model became more affordable. While they can be purchased second-hand for much lower prices than their initial retail cost, the 6th generation originally sold for $249 at 80GB and $349 at 160GB. The 7th generation 160GB version sold through Apple at the retail price of $249.
Since the 5th generation models, syncing files between an iPod and computer is done using a USB cable. The 6th generation allowed charging through FireWire, but used USB for syncing. The 7th generation devices were only available with the standard USB connection for both syncing and charging.