Transmission medium: Something that allows computers and other devices to exchange information; cables are an example.

Undo: Command used to undo the last action.

Unicode: A larger character set than ASCII. Used in some text files.

Upgrade: To install a newer version of Windows XP Professional over an existing version without removing installed programs or changing settings.

Upgrade report: A report analyzing your current system and whether it is compatible with Windows XP Professional.

URL: Uniform Resource Locator. The full path to a Web page.

User: Any individual who interacts with the computer.

User level security: Access to a file, printer, or other network resource is based on the user name.

User name: Identifies a computer's user to the network.

User profile: The user's personal preferences for his or her computer including such things as how the Desktop is displayed, network connections, printer settings, and the like.

Volumes: Different logical sections into which a hard drive may be broken up. Also, this term is sometimes used interchangeably with disks.

Wallpaper: An image to display on the background of the Desktop.

Web page: A single file on the Web.

Web site: A collection of related Web pages.

Wide area network (WAN): A network that connects people in the same company or organization but in different physical locations.

Wild card characters: The question mark (?) and/or the asterisk (*), used to replace unknown character(s) in a filename; the question mark replaces any single character, while the asterisk can represent several characters.

Window: The basic building block of Windows. Displays a file or program.

Windows Update: A program that analyzes your computer before displaying a list of available updates.

WINS (Windows Internet Name Service): Provides name-to-IP address resolution in a Windows-only network with clients using older operating systems such as Windows 95 or Windows NT; as such, it is the counterpart to DNS.

Word processor: An application used to create text documents. Allows formatting and layout.

Word wrap: Keeps the text of a text editor within the text editor's window.

Workgroup: A logical grouping of computers that share network resources without any one computer being given overall network administration responsibilities.

World Wide Web: A portion of the Internet. Uses Web sites and pages to display information.