An address book or a name and address book (NAB) is a book or a database used for storing entries called contacts. Each contact entry usually consists of a few standard fields (for example: first name, last name, company name, address, telephone number, e-mail address, fax number, mobile phone number). Most such systems store the details in alphabetical order of people's names, although in paper-based address books entries can easily end up out of order as the owner inserts details of more individuals or as people move.