d-channel

Short for Delta-channel, the channel in an ISDN connection that carries control and signaling information. Basic Rate ISDN (BRI) service consists of two 64 Kbps B-channels, and one D-channel for transmitting control information. Primary ISDN service consists of 23 B-channels (in the U.S.) or 30 B-channels (in Europe).

DAA

Data Access Arrangement, part of a modems system for interfacing with a telephone network. The DAA provides the analog circuits that electrically isolate the modem from the phone line, separating the modem from the telephone line’s higher voltage.

DAAL

(1) Data Analytics Aceleration Library.
(2) Document Access Across Languages.

Daemon

A Unix process initiated during system boot and activated automatically to perform a particular task.

Dark Data

Dark data is a type of unstructured, untagged and untapped data that is found in data repositories and has not been analyzed or processed.

Dark Web

The dark web forms a small part of the deep web, the part of the Web not indexed by usual web search engines.

DARPA

Defense Advanced Research Projects Agency.

DAS

(1) Device Access Software.

(2) Direct Attached Storage.

(3) Dual Attachment Station.

(4) Dynamically Assigned Socket.

Data Flow Model

A graphical representation produced by data flow modeling. Also referred to as a data flow diagram.

Data Link

In telecommunication a data link is the means of connecting one location to another for the purpose of transmitting and receiving digital information.

Data Link Layer

The data link layer, is the second layer of the seven-layer OSI model of computer networking. This layer is the protocol layer that transfers data between adjacent network nodes in a wide area network (WAN) or between nodes on the same local area network (LAN) segment.

Data Mart

A database or collection of databases, designed to help managers make strategic decisions about their business.  It is usually small and focused on a particular subject or department compared to data warehousing.

Data Mining

A hot buzzword for a class of database applications that look for hidden patterns in a group of data. For example, data mining software can help retail companies find customers with common interests. The term is commonly misused to describe software that presents data in new ways. True data mining software doesn't just change the presentation, but actually discovers previously unknown relationships among the data.

Data Visualisation

Is the graphical representation of information and data, so we can interpret the data easlier.

Data Warehouse

A collection of data designed to support management decision making. It contains a wide variety of data that present a coherent picture of business conditions at a single point in time.

Datagram

A self-contained, independent entity of data carrying sufficient information to be routed from source to destination without reliance on earlier exchanges between this source and destination and the transporting network.
The term has generally been replaced by the term packet.

DCC

Digital Command Control (DCC) is a standard for a system to operate model railways digitally.

DCIE

Data Center Infrastructure Efficiency, is a performance improvement metric used to calculate the energy efficiency of a data center.

DCMS

The Department for Digital, Culture, Media and Sport is a department of the United Kingdom government, with responsibility for culture and sport in England, the building of a digital economy, and some aspects of the media throughout the UK, such as broadcasting and Internet.

DCOM

Distributed Component Object Model.

DDoS

Distributed Denial of Service is when a program, controlled by the attacker, is run from many computers to prevent legitimate users from accessing that service.  This is done by making the program flood the service with requests, so making it unusable.

DDR

Dial-on-Demand Routing, is a routing technique developed by Cisco that allows a user to utilise existing telephone lines to form a WAN instead of lines that are dedicated specifically to the WAN.  It can work out cheaper than a dedicated WAN link if the data volume is low and periodic compared to continuous.

DDR-SDRAM

Double Data Rate-Synchronous DRAM, a type of SDRAM that supports data transfers on both edges of each clock cycle (the rising and falling edges), effectively doubling the memory chip's data throughput. DDR-SDRAM also consumes less power, which makes it well-suited to laptops. DDR-SDRAM is also called SDRAM II.

DDS

Data Distribution Service, is an Object Management Group standard for real-time systems that addresses data communication between the nodes of a publish/subscribe-based messaging architecture.

DDT

Data Driven Testing, is a methodology in which iterative repetition of the same sequence of test steps are performed with the help of a data source in order to drive the input values of those steps and/or the expected values while verification steps are performed.

DDWG

Digital Display Working Group is an open industry group lead by Intel, Compaq, Fujitsu, Hewlett Packard, IBM, NEC and Silicon Image. The objective of the Digital Display Working Group is to address the industry's requirements for a digital connectivity specification for high-performance PCs and digital displays.

Deadlock

A condition that occurs when two processes are each waiting for the other to complete before proceeding. The result is that both processes hang. Deadlocks occur most commonly in multitasking and client/server environments.

Debugging

Debugging is the routine process of locating and removing computer program bugs, errors or abnormalities, which is methodically handled by software programmers via debugging tools.

DEC

Digital Equipment Corporation, was an American computer company. It was best known for its minicomputers, especially its PDP and VAX lines.

Decompiler

A decompiler is a programming tool that converts an executable program or low-level/machine language into a format understandable to software programmers. It performs the operations of a compiler, which translates source code into an executable format, but in reverse.

DECT

Digital Enhanced Cordless Telecommunications.

Deep Blue

An IBM computer designed to compete against humans to play competition chess.

Deep Web

The deep web, invisible web, or hidden web are parts of the World Wide Web whose contents are not indexed by standard web search engines.

DES

Data Encryption Standard. An American Standard Algorithm used to encrypt and decrypt files.

DevOps

It is a software development methodology that combines software development (Dev) with information technology operations (Ops).

DFD

Data Flow Diagram, another name for a data flow model.

DHCP

Dynamic Host Configuration Protocol, is a communications protocol that lets network administrators manage centrally and automate the assignment of IP addresses in an organisation's network. Using the Internet Protocol, each machine that can connect to the Internet needs a unique IP address.

DHTML

1. Refers to Web content that changes each time it is viewed. For example, the same URL could result in a different page depending on any number of parameters, such as: Geographic location of the reader , Time of day , Previous pages viewed by the reader and Profile of the reader. There are many technologies for producing dynamic HTML, including CGI scripts, Server-Side Includes (SSI), cookies, Java, JavaScript, and ActiveX.

2. When capitalized, Dynamic HTML refers to new HTML extensions that will enable a Web page to react to user input without sending requests to the Web server.

Digerati

Group of people considered well-informed on the digital revolution.

DIMM

Dual In-line Memory Module, a small circuit board that holds memory chips. A single in-line memory module (SIMM) has a 32-bit path to the memory chips whereas a DIMM has 64-bit path. Because the Pentium processor requires a 64-bit path to memory, you need to install SIMMs two at a time. With DIMMs, you can install memory one DIMM at a time.

Diode

A diode is a two-terminal semiconductor electronic component that conducts current primarily in one direction. There are different types of diode.

DIP

Dual In-line Package. A type of chip housed in a rectangular casing with two rows of connecting pins on either side.

Disassembler

A disassembler is software that converts machine language instructions into assembly language instructions (also known as reverse engineering). As the term implies, a disassembler performs operations that are the inverse of operations performed by an assembler.

Distance Learning

A type of education where students work on their own at home or at the office and communicate with faculty and other students via e-mail, electronic forums, videoconferencing and other forms of computer-based communication. Distance learning is becoming especially popular with companies that need to regularly re-train their employees because it is less expensive than bringing all the students together in a traditional classroom setting. Most distance learning programs include a computer-based training (CBT) system and communications tools to produce a virtual classroom. Because the Internet and World Wide Web are accessible from virtually all computer platforms, they serve as the foundation for many distance learning systems.

DIX

The other name for a 15-pin AUI connector or a DB-15 connector. Named after Digital, Intel and Xerox who worked on the format.

DLC address

Data Link Control, the second lowest layer in the OSI Reference Model. Every network interface card (NIC) has a DLC address or DLC identifier (DLCI) that uniquely identifies the node on the network. Some network protocols, such as Ethernet and Token-Ring use the DLC addresses exclusively. Other protocols, such as TCP/IP, use a logical address at the Network Layer to identify nodes. Ultimately, however, all network addresses must be translated to DLC addresses. In TCP/IP networks, this translation is performed with the Address Resolution Protocol (ARP).

DLP

Data Loss Prevention, is a set of tools and processes used to ensure that sensitive data is not lost, misused, or accessed by unauthorized users.

DLT

Digital Linear Tape, is a form of magnetic tape and drive system used for computer data storage and archiving.

DM

Direct Message, is a term used on Twitter for a private communication with someone.

DMCA

Digital Millennium Copyright Act.

DMZ

DeMilitarised Zone, is a computer host or small network inserted as a "neutral zone" between a company's private network and the outside public network. It prevents outside users from getting direct access to a server that has company data.

DNN

Deep Neural Network. is a neural network with a certain level of complexity, a neural network with more than two layers. Deep neural networks use sophisticated mathematical modeling to process data in complex ways.

DNS

Domain Name System. Distributed Database used by TCP/IP hosts to resolve FQDNs to IP addresses.

DOM

Document Object Model, the specification for how objects in a Web page (text, images, headers, links, etc.) are represented. The DOM defines what attributes are associated with each object, and how the objects and attributes can be manipulated. Dynamic HTML (DHTML) relies on the DOM to dynamically change the appearance of Web pages after they have been downloaded to a user's browser.
Unfortunately, the two leading browsers -- Netscape Navigator and Microsoft Internet Explorer -- use different DOMs. This is one reason why their respective implementations of DHTML are so different. Both companies have submitted their DOMs to the World Wide Web Consortium (W3C) for standardization, which now has the daunting task of specifying a standard DOM without alienating either of the browser giants. The W3C's DOM specification will support both HTML and XML.

Domain

The name of an internet site, equivalent to a geographical address. Used as a more user-friendly reference to a server's IP address.

Dongle

A device that attaches to a computer to control access to a particular application. Dongles provide the most effective means of copy protection. Typically, the dongle attaches to a PC's parallel port. On Macintoshes, the dongle sometimes attaches to the ADB port. The dongle passes through all data coming through the port so it does not prevent the port from being used for other purposes. In fact, it's possible to attach several dongles to the same port.

Doorway Page

Doorway pages are web pages that are created for the deliberate manipulation of search engine indexes.

Dot-Bomb

A poor choice of investment in a dot-com business.

Dot-Com

Company or business that is established on/for the internet.

Dot-Corp

An internet business established by a 'bricks and mortar' company, e.g. Egg from the Prudential.

Dot-Hon

A well established dot-com executive.

Double Opt In

Double opt-ins ensure that customers who have subscribed to your emails did indeed mean to opt in by reconfirming by email.

Downloading

Transferring data or files from another computer onto your own.

Dox

Search for and publish private or identifying information about (a particular individual) on the Internet, typically with malicious intent.

DPI

Dots per Inch, is a measure of the sharpness of the display of the image on the monitor, printer or scanner. The dot pitch determines the absolute limit of the possible dots per inch. However, the displayed resolution of pixels (picture elements) that is set up for the display is usually not as fine as the dot pitch. The dots per inch for a given picture resolution will differ based on the overall screen size since the same number of pixels are being spread out over a different space. Some users prefer the term "pixels per inch (PPI)" as a measure of display image sharpness, reserving dpi for use with the print medium.

DRAM

Dynamic Random Access Memory, a type of memory used in most personal computers.

DRM

Digital Rights Management, is systems that restrict the use of digital files in order to protect the interests of copyright holders.

DSDM

Dynamic Systems Development Method, a software application development methodology.

DSL

Digital Subscriber Line.

DSRC

Dedicated Short Range Communication.

DSSS

Direct-Sequence Spread Spectrum. DSSS is one of two types of spread spectrum radio, the other being FHSS. DSSS is a transmission technology used in LAWN transmissions where a data signal at the sending station is combined with a higher data rate bit sequence, or chipping code, that divides the user data according to a spreading ratio. The chipping code is a redundant bit pattern for each bit that is transmitted, which increases the signal's resistance to interference. If one or more bits in the pattern are damaged during transmission, the original data can be recovered due to the redundancy of the transmission.

DSTN

Double-layer SuperTwist Nematic, a passive-matrix LCD technology that uses two display layers to counteract the colour shifting that occurs with conventional supertwist displays.

DTD

Document Type Definition. A DTD states what tag and attribute are used to describe content in an SGML document, where each tag is allowed, and which tags can appear within other tags.

DTV

Digital Television, a means of broadcasting TV pictures and sound digitally, that as well as the potential for enhanced picture and sound will allow internet access and interactive features.

Dumb Terminal

A display monitor that has no processing capabilities. A dumb terminal is simply an output device that accepts data from the CPU.

DVD-ROM

Digital Versatile Disc-Read Only Memory, is a read-only digital versatile disc commonly used for storing large software applications or films. A DVD-ROM stores around 4.38 GB of data.

DVI

(1) Short for Digital Visual Interface, a digital interface standard created by the Digital Display Working Group (DDWG) to convert analog signals into digital signals to accommodate both analog and digital monitors. Data is transmitted using the transition minimised differential signalling (TMDS) protocol, providing a digital signal from the PC's graphics subsystem to the display.

(2) Short for Digital Video Interactive, a now-defunct technology developed by General Electric that enables a computer to store and display moving video images like those on television. DVI is a hardware-only codec (compression/decompression) technology. A competing hardware codec, which has become much more popular, is MPEG. Intel has developed a software version of the DVI algorithm, which it markets under the name Indeo.

(3) Short for Device Independent, a file format used by the TeX typography system.