The CD's design drew inspiration from vinyl records: Like the grooves on a record, CDs are engraved with a spiral of tiny pits that are scanned by a laser - the equivalent of a record player's needle. The reflected light is encoded into millions of 0s and 1s: a digital file.
Because the pits are covered with plastic and the laser's light doesn't wear them down, the CD never loses sound quality.
Legends abound about how the size of the CD was chosen: Some said it matched a Dutch beer coaster; others believe a famous conductor or Sony executive wanted it just long enough for Beethoven's 9th Symphony.
iTunes Top Downloads -- April 25, 2010 This is a moment in time snapshot of the current top downloads from iTunes. We take a snapshot each week at the same time and post it here. To preview the songs, click on a link.