The stripe on a credit or ATM card is magnetized. The data is analog, not digital; therefore, it is easy to decipher. A card reader is not unlike the head on a tape deck; it reads the information like recorded music. The stripe on the back of bank cards has three tracks of data that contain information such as account number, accountholder's name , card expiration date, and PIN code. There is also a field for discretionary data, which might include further security information or links to other accounts.