Address book

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. Many address books use small ring binders that allow adding, removing and shuffling of pages to make room.

Little black book
A related term that has entered the popular lexicon is little black book (or simply black book). Such books are used as dating guides, listing people who the owner has dated in the past or hopes to in the future, and details of their various relationships. More explicit variations are guides for sexual partners. It is unclear how prevalent this is in practice or when it originated, though such books have been mentioned in many pieces of popular culture. For example, the 1953 film version of Kiss Me, Kate features a musical scene in which Howard Keel's character laments the loss of the social life he enjoyed before marriage, naming numerous female romantic encounters while perusing a miniature black book. More recently, the mid-2000s Guinness Brewmasters advertising campaign features the "little black book" as an invention of one of the brewmasters.

Software address book
Address books can also appear as software designed for this purpose, such as the "Address Book" application included with Apple Inc.'s Mac OS X. Simple address books have been incorporated into e-mail software for many years, though more advanced versions have emerged in the 1990s and beyond; and also in mobile phones.

A personal information manager (PIM) integrates an address book, calendar, task list, and sometimes other features.

Entries can be imported and exported from the software in order to transfer them between programs or computers. The common file formats for these operations are:
 * LDIF (*.ldif, *.ldi)
 * Tab delimited (*.tab, *.txt)
 * Comma-separated (*.csv)
 * vCard (*.vcf)

Individual entries are frequently transferred as vCards (*.vcf), which are roughly comparable to physical business cards. And some software applications like Lotus Notes and Open Contacts can handle a vCard file containing multiple vCard records.

Online address book
An online address book typically enables users to create their own web page (or profile page) which is then indexed by search engines like Google and Yahoo. This in turn enables users to be found by other people via a search of their name and then contacted via their web page containing their personal information. Ability to find people registered with online address books via search engine searches usually varies according to the commonness of the name and the amount of results for the name. Typically users of such systems can synchronize their contact details with other users that they know to ensure that their contact information is kept up to date. Examples of online address books include GlipMe, AboutOne, Evercontact, NexusPad Plaxo, Telnic, Unyk, conXt, and WikiWorldBook.

Network address book
Currently, most people have many different address books: their email accounts, their mobile phone, and the "friends lists" on their social networks. A network address book allows them to organize and manage all of their address books through a single interface and share their contacts across their different address books and social networks.