A-D

access violation error

Errors caused by corrupt files or low system resources. Access violation errors can occur because of inaccurate calculations, when launching programs, or when code is poorly written.

Active Directory directory service

A centralized database that contains information about a network’s users, workstations, servers, printers, and other resources. Active Directory (found on a domain controller) determines who can access what and to what degree. Active Directory is essential for maintaining, organizing, and securing the resources on a larger network; it allows network administrators to centrally manage resources; and it is extensible—it can be configured to grow and to be personalized for any company.

ActiveX control

Small programs and animations on Web pages. ActiveX controls are downloaded to and run on a computer to enhance the Web experience.

adware

Software that shows ads that the program thinks the user would like to see. Adware is usually installed unknowingly and knows what a user likes because it watches what sites the user visits while online. Adware is a form of spyware.

AutoRecover files

Files that are saved automatically when an application shuts down unexpectedly. AutoRecover files can help a user recover a document when the power goes out or when a computer shuts down unexpectedly.

basic input/output system (BIOS)

A computer’s BIOS program determines in what order the computer searches for system files on bootup, manages communication between the operating system and the attached devices on bootup, and is an integral part of the computer.

bit

A binary digit, the smaller unit of information holding data on a computer. A single bit can only hold one of two values: 0 or 1.

BIOS

See basic input/output system.

broadcast storm

When a single message is sent to all hosts on a network or network segment. Broadcast storms can be used by attackers to disable a network by sending too many messages for the network to handle.

byte

A basic unit of computer storage. A byte contains 8 bits.

cache

An area of the hard disk that holds temporary files. In the context of Internet Explorer, temporary Internet files are cached so a user can use the Back and Forward buttons, access History, and use offline files and folders. Retrieving information from the cache is much faster than retrieving information from the Internet.

COM port

A computer’s communication port. This port, which allows data to be sent one byte at a time, is often referred to as a serial port.

compact privacy policy

A website’s privacy policy. The policy details what information is collected from visitors, who the information is given to, and how the owners of the Web site use the information. It also conforms to the Platform for Privacy Preferences (P3P).

compressed drive

A drive that has been condensed to take up less space on the hard disk by using a compression tool such as NTFS compression utilities.

Conflicts folder

A folder in Outlook 2003 that holds multiple copies of conflicting items in the mailbox. If multiple changes have been made to an item, but the item is not updated correctly in the Navigation pane, check this folder.

cookie

A small text file that contains information about you and your computer. Web sites place cookies on computers that visit them so that they can personalize the user’s next visit. Generally, cookies are harmless.

device driver

Software that is used to allow a computer and a piece of hardware to communicate. Device drivers that are incompatible, corrupt, outdated, or of the wrong version for the hardware can cause errors that are difficult to diagnose.

DHCP

See Dynamic Host Configuration Protocol.

disk quota

A restriction that can be placed on users so that they can only use a predefined amount of a hard disk’s available space.

DLL

See dynamic-link library.

DNS

See Domain Name System.

Domain Name System (DNS)

A service that resolves host names to IP addresses for clients on a network. This service allows users to type in a name such as www.microsoft.com instead of its IP address.

Downloaded Program Files

A folder on a computer’s hard disk that contains downloaded program files. These files can be ActiveX controls and Java applets, which are downloaded automatically from the Internet when you view certain pages.

Dynamic Host Configuration Protocol (DHCP)

A service that assigns TCP/IP addresses automatically to clients on a network. DHCP servers provide this service.

dynamic-link library (DLL)

DLL files, which are shared among multiple components of a computer and its applications, are used to run operating system components and applications. Missing DLL files cause multiple problems and usually generate an error message.