Windows Glossary “Windows Dictionary” (D)

D-channel
A separate channel of an ISDN line that is used for ISDN signaling. For ISDN Basic Rate Interface (BRI), the D-channel is 16 kilobits per second (Kbps). For ISDN Primary Rate Interface (PRI), the D-channel is 64 Kbps. D-channel is also called data channel.

daily backup
A backup that copies all selected files that have been modified the day the daily backup is performed. The backed-up files are not marked as having been backed up (in other words, the archive attribute is not cleared).

Data Communications Equipment (DCE)
One of two types of hardware connected by an RS-232-C serial connection, the other being a Data Terminal Equipment (DTE) device. A DCE is an intermediary device that often transforms input from a DTE before sending it to a recipient. A modem, for example, is a DCE that modulates data from a microcomputer (DTE) and sends it along a telephone connection.

Data Link Control (DLC)
An address that uniquely identifies a node on a network. Every network adapter has a DLC address or DLC identifier (DLCI). Some network protocols, such as Ethernet and Token Ring, use DLC addresses exclusively. Other protocols, such as TCP/IP, use a logical address at the OSI Network layer to identify nodes.
However, all network addresses must eventually be translated to DLC addresses. In TCP/IP networks, this translation is performed by the Address Resolution Protocol (ARP).

data packet
A unit of information transmitted as a whole from one device to another on a network.

Data Terminal Equipment (DTE)
In the RS-232-C hardware standard, any device, such as a remote access server or client, that has the ability to transmit information in digital form over a cable or a communications line.

data-overrun error
A state in which the sending computer is transmitting characters faster than the receiving computer can accommodate them. If this problem persists, reduce the bits-per-second (bps) rate.

datagram
One packet, or unit, of information that includes relevant delivery information, such as the destination address, that is sent through a packet-switching network.

dead-letter queue
For Message Queuing, a queue that stores nontransactional messages that are undeliverable or expired. These queues store failed messages on the computer on which the message expired. Messages in these queues are written to disk and are therefore recoverable.

debugger
A program designed to aid in detecting, locating, and correcting errors in another program by allowing the programmer to step through the program, examine the data, and monitor conditions such as the values of variables.

dedicated adapter
The network adapter that, when using multiple network adapters in each host of a Network Load Balancing cluster, handles network traffic not related to cluster operations (the traffic for individual hosts on the network). This adapter is programmed with the host's dedicated IP address.

default button
In some dialog boxes, the command button that is selected or highlighted when the dialog box is initially displayed. The default button has a bold border, indicating that it will be chosen automatically if you press ENTER. You can override a default button by clicking Cancel or another command button.

default gateway
A configuration item for the TCP/IP protocol that is the IP address of a directly reachable IP router. Configuring a default gateway creates a default route in the IP routing table.

default host
The host with the highest host priority for which a drainstop command is not in progress. After convergence, the default host handles all of the network traffic for TCP and UDP ports that are not otherwise covered by port rules.

default network
In the Macintosh environment, the physical network on which the processes of a server reside as nodes and on which the server appears to users. The default network of the server must be one to which that server is attached. Only servers on AppleTalk Phase 2 internets have default networks.

default printer
The printer to which a computer sends documents if you select the Print command without first specifying which printer you want to use with a program. You can have only one default printer; it should be the printer you use most often.

default user
The profile that serves as a basis for all user profiles. Every user profile begins as a copy of the default user profile.

default zone
The zone to which all Macintosh clients on the network are assigned by default.

defragmentation
The process of rewriting parts of a file to contiguous sectors on a hard disk to increase the speed of access and retrieval. When files are updated, the computer tends to save these updates on the largest continuous space on the hard disk, which is often on a different sector than the other parts of the file. When files are thus fragmented, the computer must search the hard disk each time the file is opened to find all of the file's parts, which slows down response time.

delegation
The ability to assign responsibility for management and administration of a portion of the namespace to another user, group, or organization.
For DNS, a name service record in the parent zone that lists the name server authoritative for the delegated zone.

denial-of-service attack
An attack in which an attacker exploits a weakness or a design limitation of a network service to overload or halt the service, so that the service is not available for use. This type of attack is typically launched to prevent other users from using a network service such as a Web server or a file server.

dependency
A relationship of reliance between two resources that makes it necessary for them to run in the same group on the same node. For example, an application is dependent on the disks that contain its data resources.

dependency tree
A diagram for visualizing the dependency relationships between resources.

dependent client
For Message Queuing, a computer that requires synchronous access to a Message Queuing server to perform all standard message queuing operations, such as sending and receiving messages and creating queues.

descendent key
All the subkeys that appear when a key in the registry is expanded. A descendent key is the same as a subkey.

desired zone
The zone in which AppleTalk network integration appears on the network.

desktop
The on-screen work area on which windows, icons, menus, and dialog boxes appear.

desktop pattern
A design that appears across your desktop. You can create your own pattern or select a pattern provided by Windows.

destination document
The document into which a package or a linked or embedded object is being inserted. For an embedded object, this is sometimes also called the container document.

details pane
The pane in the Microsoft Management Console (MMC) that displays the details for the selected item in the console tree. The details can be a list of items or they can be administrative properties, services, and events that are acted on by a snap-in.

device
Any piece of equipment that can be attached to a network or computer; for example, a computer, printer, joystick, adapter, or modem card, or any other peripheral equipment. Devices normally require a device driver to function with Windows.

device conflict
A conflict that occurs when the same system resources have been allocated to two or more devices. System resources include interrupt request (IRQ) lines, direct memory access (DMA) channels, input/output (I/O) ports, and memory addresses.

device driver
A program that allows a specific device, such as a modem, network adapter, or printer, to communicate with the operating system. Although a device might be installed on your system, Windows cannot use the device until you have installed and configured the appropriate driver.
If a device is listed in the Hardware Compatibility List (HCL), a driver is usually included with Windows. Device drivers load automatically (for all enabled devices) when a computer is started, and thereafter run invisibly.

device fonts
Fonts that reside in your printer. They can be built into the printer itself or provided by a font cartridge or font card.

Device Manager
An administrative tool that you can use to manage the devices on your computer. Using Device Manager, you can view and change device properties, update device drivers, configure device settings, and uninstall devices.

DFS link
An element in the Distributed File System (DFS) namespace that lies below the root and maps to one or more targets, each of which corresponds to a shared folder or another DFS root.

DFS root
The starting point of the Distributed File System (DFS) namespace. The root is often used to refer to the namespace as a whole. A root maps to one or more root targets, each of which corresponds to a shared folder on a server.

DFS topology
The overall logical hierarchy of the Distributed File System (DFS), including elements such as roots, links, shared folders, and replica sets, as depicted in the DFS administrative console. This is not to be confused with the DFS namespace, which is the logical view of shared resources seen by users.

DHCP client
Any network-enabled device that supports the ability to communicate with a DHCP server for the purpose of obtaining dynamic leased IP configuration and related optional parameters information.

DHCP option
Address configuration parameters that a DHCP service assigns to clients. Most DHCP options are predefined, based on optional parameters defined in Request for Comments (RFC) 1542, although extended options can be added by vendors or users.

DHCP server
A computer running the Microsoft DHCP service that offers dynamic configuration of IP addresses and related information to DHCP-enabled clients.

DHCP service resource
A resource type that provides DHCP services from a cluster.

DHCP/BOOTP Relay Agent
The agent program or component responsible for relaying DHCP and BOOTP broadcast messages between a DHCP server and a client across an IP router. A DHCP relay agent supports DHCP/BOOTP message relay as defined in RFCs 1541 and 2131. The DHCP Relay Agent service is managed using the Routing and Remote Access service.

dial location
The country code, area code, and specific dialing requirements for the place you are dialing from. Once you have created a dial location, you can select it to apply the dialing requirements to all your calls. To change dialing locations, select or create a different one.

dial-up connection
The connection to your network if you are using a device that uses the telephone network. This includes modems with a standard phone line, ISDN cards with high-speed ISDN lines, or X.25 networks.
If you are a typical user, you may have one or two dial-up connections, for example, to the Internet and to your corporate network. In a more complex server situation, multiple network modem connections might be used to implement advanced routing.

dialog box
A secondary window that contains buttons and various kinds of options through which you can carry out a particular command or task.

dictionary attack
A method of guessing a user's password or PIN by trying every word in the dictionary until successful.

differential backup
A backup that copies files created or changed since the last normal or incremental backup. It does not mark files as having been backed up (in other words, the archive attribute is not cleared). If you are performing a combination of normal and differential backups, restoring files and folders requires that you have the last normal as well as the last differential backup.

differential data
Saved copies of changed data that can be applied to an original volume to generate a volume shadow copy.

digital signature
A means for originators of a message, file, or other digitally encoded information to bind their identity to the information. The process of digitally signing information entails transforming the information, as well as some secret information held by the sender, into a tag called a signature. Digital signatures are used in public key environments, and they provide nonrepudiation and integrity services.

Digital Signature Standard (DSS)
A standard that uses the Digital Signature Algorithm (DSA) for its signature algorithm and SHA-1 as its message hash algorithm. DSA is a public-key cipher that is used only to generate digital signatures and cannot be used for data encryption.

Digital Subscriber Line (DSL)
A type of high-speed Internet connection using standard telephone wires. This is also referred to as a broadband connection.

digital video disc (DVD)
A type of optical disc storage technology. A digital video disc (DVD) looks like a CD-ROM disc, but it can store greater amounts of data. DVDs are often used to store full-length movies and other multimedia content that requires large amounts of storage space.

direct cable connection
A link between the I/O ports of two computers created with a single cable rather than a modem or other interfacing devices. In most cases, a direct cable connection is made with a null modem cable.

direct memory access (DMA)
Memory access that does not involve the microprocessor. DMA is frequently used for data transfer directly between memory and a peripheral device such as a disk drive.

directory partition
A contiguous subtree of the directory that forms a unit of replication. A given replica is always a replica of some directory partition. The directory always has at least three directory partitions:
• The schema, which defines the object classes and attributes contained in Active Directory.
• The configuration, which identifies the domain controllers, replication topology and other related information about the domain controllers within a specific implementation of Active Directory.
• One or more domains that contain the actual directory object data.
A domain controller always stores the partitions for the schema, configuration, and its own (and no other) domain. The schema and configuration are replicated to every domain controller in the domain tree or forest. The domain is replicated only to domain controllers for that domain. A subset of the attributes for all domain objects is replicated to the global catalog.

directory service
Both the directory information source and the service that make the information available and usable. A directory service enables the user to find an object given any one of its attributes.

DirectX
An extension of the Microsoft Windows operating system. DirectX technology helps games and other programs use the advanced multimedia capabilites of your hardware.

disable
To make a device nonfunctional. For example, if you disable a device in a hardware configuration, you cannot use the device when your computer uses that hardware configuration. Disabling a device frees the resources that were allocated to the device.

discretionary access control list (DACL)
The part of an object's security descriptor that grants or denies specific users and groups permission to access the object. Only the owner of an object can change permissions granted or denied in a DACL; thus, access to the object is at the owner's discretion.

disk
A storage device that is attached to a computer.

disk configuration information
Information in the Windows registry on assigned drive letters, simple volumes, striped volumes, mirrored volumes, spanned volumes, and RAID-5 volumes. You can change the disk configuration by using Disk Management.

dismount
To remove a removable tape or disc from a drive.

distinguished name
A name that uniquely identifies an object by using the relative distinguished name for the object, plus the names of container objects and domains that contain the object. The distinguished name identifies the object as well as its location in a tree. Every object in Active Directory has a distinguished name. A typical distinguished name might be
CN=MyName,CN=Users,DC=Microsoft,DC=Com
This identifies the MyName user object in the microsoft.com domain.

distribution group
A group that is used solely for e-mail distribution and that is not security-enabled. Distribution groups cannot be listed in discretionary access control lists (DACLs) used to define permissions on resources and objects. Distribution groups can be used only with e-mail applications (such as Microsoft Exchange) to send e-mail to collections of users. If you do not need a group for security purposes, create a distribution group instead of a security group.

DNS Server
A service that maintains information about a portion of the Domain Name System (DNS) database and responds to and resolves DNS queries. A computer running this service is also known as a DNS server.

DNS suffix
For DNS, a character string that represents a domain name. The DNS suffix shows where a host is located relative to the DNS root, specifying a host?s location in the DNS hierarchy. Usually, DNS suffix describes the latter portion of a DNS name, following one or more of the first labels of a DNS name.

dock
To connect a laptop or notebook computer to a docking station.

docking station
A unit for housing a portable computer that contains a power connection, expansion slots, and connections to peripherals, such as a monitor, printer, full-sized keyboard, and mouse. The docking station turns the portable computer into a desktop computer.

document
Any self-contained piece of work created with an application program and, if saved on disk, given a unique file name by which it can be retrieved.

domain
A group of computers that are part of a network and share a common directory database. A domain is administered as a unit with common rules and procedures. Each domain has a unique name.
An Active Directory domain is a collection of computers defined by the administrator of a Windows network. These computers share a common directory database, security policies, and security relationships with other domains. An Active Directory domain provides access to the centralized user accounts and group accounts maintained by the domain administrator. An Active Directory forest is made up of one or more domains, each of which can span more than one physical location.
A DNS domain is any tree or subtree within the DNS namespace. Although the names for DNS domains often correspond to Active Directory domains, DNS domains should not be confused with Active Directory domains.

domain controller
In a Windows domain environment, a computer running Active Directory that manages user access to a network, which includes logging on, authentication, and access to the directory and shared resources.

domain controller locator (Locator)
An algorithm that runs in the context of the Net Logon service and that finds domain controllers on a Windows 2000 network. Locator can find domain controllers by using DNS names (for IP/DNS-compatible computers) or by using NetBIOS names (for computers that are running Windows 3.x, Windows for Workgroups, Windows NT 3.5 or later, Windows 95, or Windows 98, or it can be used on a network where IP transport is not available).

domain DFS
An implementation of DFS in which DFS topological information is stored in Active Directory. Because this information is made available on multiple domain controllers in the domain, domain DFS provides fault-tolerance for any distributed file system in the domain.

domain local group
A security or distribution group that can contain universal groups, global groups, and accounts from any domain in the domain tree or forest. A domain local group can also contain other domain local groups from its own domain. Rights and permissions can be assigned only at the domain containing the group.

domain name
The name given by an administrator to a collection of networked computers that share a common directory. Part of the Domain Name System (DNS) naming structure, domain names consist of a sequence of name labels separated by periods.

Domain Name System (DNS)
A hierarchical, distributed database that contains mappings of DNS domain names to various types of data, such as IP addresses. DNS enables the location of computers and services by user-friendly names, and it also enables the discovery of other information stored in the database.

domain namespace
The database structure used by the Domain Name System (DNS).

domain naming master
The domain controller assigned to control the addition or removal of domains in the forest. At any time, there can be only one domain naming master in the forest.

domain of origin
The parent DNS domain name that is used to root either a zone or a resource record within a zone. This name is joined to the end of unqualified or relative domain names to form a fully qualified domain name (FQDN) within the zone. In DNS Manager, the domain of origin will correspond to Zone name as it appears in the Add Zone Wizard or the name that appears in the Parent domain name field for any resource records created within the zone.

domain tree
In DNS, the inverted hierarchical tree structure that is used to index domain names. Domain trees are similar in purpose and concept to the directory trees used by computer filing systems for disk storage.
For example, when numerous files are stored on disk, directories can be used to organize the files into logical collections. When a domain tree has one or more branches, each branch can organize domain names used in the namespace into logical collections.
In Active Directory, a hierarchical structure of one or more domains, connected by transitive, bidirectional trusts, that forms a contiguous namespace. Multiple domain trees may belong to the same forest.

dots per inch (DPI)
The standard used to measure screen and printer resolution, expressed as the number of dots that a device can display or print per linear inch. The greater the number of dots per inch, the better the resolution.

double-byte characters
A set of characters in which each character is represented by two bytes. Some languages, such as Japanese, Chinese, and Korean, require double-byte character sets.

downloadable fonts
A set of characters stored on disk and sent (downloaded) to a printer's memory when needed for printing a document. Downloadable fonts are most commonly used with laser printers and other page printers, although many dot-matrix printers can accept some of them. Downloadable fonts are also called soft fonts.

drag
To move an item on the screen by selecting the item and then pressing and holding down the mouse button while moving the mouse. For example, you can move a window to another location on the screen by dragging its title bar.

drain
For Network Load Balancing, a command that disables new traffic handling for the rule whose port range contains the specified port. All ports specified by the port rule are affected.

drainstop
For Network Load Balancing, a command that disables all new traffic handling on the specified hosts. The hosts then enter draining mode to complete existing connections.
While draining, hosts remain in the cluster and stop their cluster operations when there are no more active connections. To terminate draining mode, explicitly stop cluster mode with the stop command, or restart new traffic handling with the start command. To drain connections from a specific port, use the drain command.

drive
An area of storage that is formatted with a file system and has a drive letter. The storage can be a floppy disk, a CD, a hard disk, or another type of disk. You can view the contents of a drive by clicking its icon in Windows Explorer or My Computer.

drive letter
The naming convention for disk drives on IBM and compatible computers. Drives are named by letter, beginning with A, followed by a colon.

drop folder
In the Macintosh environment, a folder for which you have the Make Changes permission but not the See Files or See Folders permission. You can copy files into a drop folder, but you cannot see what files and subfolders the drop folder contains.

dual boot
A computer configuration that can start two different operating systems.

duplex
A system capable of transmitting information in both directions over a communications channel.

DVD decoder
A hardware or software component that allows a digital video disc (DVD) drive to display movies on your computer screen.

DVD drive
A disk storage device that uses digital video disc (DVD) technology. A DVD drive reads both CD-ROM and DVDs; however, you must have a DVD decoder to display DVD movies on your computer screen.

DWORD

A data type composed of hexadecimal data with a maximum allotted space of 4 bytes.
dynamic data exchange (DDE)
A form of interprocess communication (IPC) implemented in the Microsoft Windows family of operating systems. Two or more programs that support dynamic data exchange (DDE) can exchange information and commands.

dynamic disk
A physical disk that can be accessed only by Windows 2000 and Windows XP. Dynamic disks provide features that basic disks do not, such as support for volumes that span multiple disks. Dynamic disks use a hidden database to track information about dynamic volumes on the disk and other dynamic disks in the computer. You convert basic disks to dynamic by using the Disk Management snap-in or the DiskPart command line utility. When you convert a basic disk to dynamic, all existing basic volumes become dynamic volumes.

Dynamic Host Configuration Protocol (DHCP)
A TCP/IP service protocol that offers dynamic leased configuration of host IP addresses and distributes other configuration parameters to eligible network clients. DHCP provides safe, reliable, and simple TCP/IP network configuration, prevents address conflicts, and helps conserve the use of client IP addresses on the network.
DHCP uses a client/server model where the DHCP server maintains centralized management of IP addresses that are used on the network. DHCP-supporting clients can then request and obtain lease of an IP address from a DHCP server as part of their network boot process.

dynamic storage
A storage method in Windows that allows disk and volume management without requiring operating system restart.

dynamic update
An updated specification to the Domain Name System (DNS) standard that permits hosts that store name information in DNS to dynamically register and update their records in zones maintained by DNS servers that can accept and process dynamic update messages.

dynamic volume
A volume that resides on a dynamic disk. Windows supports five types of dynamic volumes: simple, spanned, striped, mirrored, and RAID-5. A dynamic volume is formatted by using a file system, such as FAT or NTFS, and it has a drive letter assigned to it.

dynamic-link library (DLL)
An operating system feature that allows executable routines (generally serving a specific function or set of functions) to be stored separately as files with .dll extensions. These routines are loaded only when needed by the program that calls them.