data
`
`data compaction
`
`data n. Plural of the Latin datum, meaning an item of infor-
`mation. In practice, data is often used for the singular as well
`as the plural form of the noun. See also datum. Compare
`information.
`
`Data Access Objects n. A data access interface that
`communicates with Microsoft Jet and ODBC-compliant
`data sources to connect to, retrieve, manipulate, and
`update data and the database structure. Acronym: DAO.
`
`data acqulsltlon n. The process of obtaining data from
`another source, usually one outside a specific system.
`
`data aggregate n. A collection of data records. It usu—
`ally includes a description of the placement of the data
`blocks and their relation to the entire set.
`
`data attrlbute n. Structural information about data that
`
`describes its context and meaning.
`
`data bank n. Any substantial collection of data.
`
`database n. A file composed of records, each containing
`fields together with a set of operations for searching, sort-
`ing, recombining, and other functions. Acronym: DB.
`
`database admlnlstrator n. One who manages a data-
`base. The administrator determines the content, internal
`structure, and access strategy for a database, defines secu-
`rity and integrity, and monitors performance. Acronym:
`DBA. Also called: database manager.
`
`database analyst n. One who provides the analytic
`functions needed to design and maintain applications
`requiring a database.
`
`database deslgner n. One who designs and implements
`functions required for applications that use a database.
`
`database englne n. The program module or modules
`that provide access to a database management system
`(DBMS).
`
`database machlne n. 1. A peripheral that executes data-
`base tasks, thereby relieving the main computer from per-
`forming them. 2. A database server that performs only
`database tasks.
`
`database management system n. A software interface
`between the database and the user. A database manage-
`ment system handles user requests for database actions
`and allows for control of security and data integrity
`requirements. Acronym: DBMS. Also called: database
`manager. See also database engine.
`database manager 71. See database administrator, data-
`base management system.
`
`database publlshlng n. The use of desktop publishing or
`Internet technology to produce reports containing infor—
`mation obtained from a database.
`
`database server n. A network node, or station, dedi-
`cated to storing and providing access to a shared database.
`Also called: database machine.
`
`database structure n. A general description of the for-
`mat of records in a database, including the number of
`fields, specifications regarding the type of data that can be
`entered in each field, and the field names used.
`
`data blt n. In asynchronous communications, one of a
`group of from 5 to 8 bits that represents a single character
`of data for transmission. Data bits are preceded by a start
`bit and followed by an optional parity bit and one or more
`stop bits. See also asynchronous transmission, bit, com-
`munications parameter.
`
`data buffer n. An area in memory where data is tempo-
`rarily stored while being moved from one location to
`another. See also bufferl.
`
`data bus n. See bus.
`
`data cable n. Fiber-optic or wire cable used to transfer
`data from one device to another.
`
`data capture n. 1. The collection of information at the
`time of a transaction. 2. The process of saving on a storage
`medium a record of interchanges between a user and a
`remote information utility.
`
`data carrler n. See carrier (definition 1).
`
`Data Carrler Detected n. See DCD (definition 1).
`
`data chalnlng n. The process of storing segments of data
`in noncontiguous locations while retaining the ability to
`reconnect them in the proper sequence.
`
`data channel n. See channel (definition 1).
`
`data closet n. See wiring closet.
`
`data collectlon n. 1. The process of acquiring source
`documents or data. 2. The grouping of data by means of
`classification, sorting, ordering, and other organizing
`methods.
`
`datacom n. Short for data communications See
`communications.
`
`data communlcatlons n. See communications.
`
`data compactlon n. See data compression.
`
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`

`data compression
`
`data file
`
`data comprosslon n. A means of reducing the amount of
`space or bandwidth needed to store or transmit a block of
`data, used in data communications, facsimile transmis-
`sion, file storage and transfer, and CD-ROM publishing.
`Also called: data compaction.
`
`data conferenclng n. Simultaneous data communica-
`tion among geographically separated participants in a
`meeting. Data conferencing involves Whiteboards and
`other software that enable a single set of files at one loca-
`tion to be accessed and modified by all participants. See
`the illustration. See also desktop conferencing, white-
`board. Compare video conferencing.
`
`
`
`Data conferencing.
`
`data control n. The aspect of data management con-
`cerned with trackng how and by whom data is used,
`accessed, altered, owned, and reported on.
`
`data converslon 11. Changing the way information is rep-
`resented in a document or file—for instance, changing
`binary representation to decimal or hexadecimal.
`
`data corruptlon n. See corruption.
`
`data declaratlon n. A statement in a program that speci-
`fies the characteristics of a variable. The requirements for
`data declarations vary among different programming lan-
`guages but can include such values as variable name, data
`type, initial value, and size specification. See also array,
`data type, recordl, variable.
`data deflnltlon language 11. A language that defines all
`attributes and properties of a database, especially record
`layouts, field definitions, key fields, file locations, and
`storage strategy. Acronym: DDL.
`
`data descrlptlon language 11. A language designed spe-
`cifically for declaring data structures and files. See also
`data definition language.
`
`data dlctlonary n. A database containing data about all
`the databases in a database system. Data dictionaries store
`all the various schema and file specifications and their
`locations. They also contain information about which pro-
`grams use which data and which users are interested in
`which reports.
`
`data dlrectory It. See catalog, data dictionary.
`data-drlven attack 11. A form of attack in which mali-
`
`cious code is hidden in a program or other innocuous data.
`When the data is executed, the virus or other destructive
`code is activated. A data-driven attack is typically used to
`bypass a firewall or other security measures.
`
`data-drlven processlng n. A form of processing where
`the processor or program must wait for data to arrive
`before it can advance to the next step in a sequence. Com-
`pare: demand—driven processing.
`
`data element n. A single unit of data. Also called: data
`item. See also data field.
`
`data encapsulatlon n. A method of dealing with com-
`puters with Year 2000 problems that entailed modifying
`the input and output logic of a program, leaving the actual
`data unchanged as it was processed. The input logic was
`modified to reflect a date in the past that the computer
`could handle that paralleled the current calendar. When
`output was generated, the output logic changed the data to
`reflect the correct date.
`
`data encryptlon n. See encryption.
`
`data encryptlon key 11. A sequence of secret informa-
`tion, such as a string of decimal numbers or binary digits,
`that is used to encrypt and decrypt data. Acronym: DEK.
`See also decryption, encryption, key (definition 3).
`
`data encryptlon standard 21. See DES.
`
`data entry 71. The process of writing new data to com-
`puter memory.
`
`data/fax modem n. A modem that can handle both
`serial data and facsimile images to either send or receive
`transmissions.
`
`data fleld n. A well-definedportion of a data record, such
`as a column in a database table.
`
`data field masklng n. The process of filtering or select-
`ing part of a data field to control the way it is returned and
`displayed.
`
`data file n. A file consisting of data in the form of text,
`numbers, or graphics, as distinct from a program file of
`commands and instructions. Compare program file.
`
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`

`data flow
`
`data management
`
`computer and a printer or a main computer and a temli-
`nal. Sometimes the term is extended to include equip-
`ment, such as a modem, that enables transmission and
`receiving. Such devices follow protocols that govern data
`transmission. See also communications protocol, data-
`link layer, DCE (definition I), DTE.
`Data Link Connection ldentlIIer n. A virtual circuit on
`
`frame relay networks that permanently identifies the path
`to a particular destination. See also frame relay, virtual
`circuit.
`
`Data Link Control n. See DLC.
`
`data llnk escape n. In data transmission, a control char-
`acter that changes the meaning of the characters immedi-
`ately following it.
`
`data-llnk layer 11. The second of seven layers in the ISO/
`OSI reference model for standardizing computer-to-com—
`puter communications. The data-link layer is one layer
`above the physical layer. Its concern is packaging and
`addressing data and managing the flow of transmissions. It
`is the lowest of the three layers (data-link, network, and
`transport) involved in actually moving dam between devices.
`See the illustration. See also ISO/OSI reference model.
`
`data flow or dataflow n. 1. The movement of data
`
`through a system, from entry to destination. 2. In parallel
`processing, a design in which a calculation is made either
`when all necessary data is available (data-driven process-
`ing) or when other processors request the data (demand-
`driven processing). See also parallel processing.
`
`data fork n. In Macintosh files, the part of a stored docu-
`ment that contains user-supplied information, such as the
`text of a word-processing document. A Macintosh file can
`have a data fork, a resource fork (which contains informa-
`tion such as program code, font data, digitized sound, or
`icons), and a header. All three parts are used by the operat-
`ing system in file management and storage See also
`resource (definition 2), resource fork.
`
`data format 71. The structure applied to data by an appli-
`cation program to provide a context in which the data can
`be interpreted.
`
`data frame 11. A packet of information transmitted as a
`unit on a network. Data frames are defined by the network’s
`data-link layer and exist only on the wire between network
`nodes. See also data-link layer, frame (definition 2).
`
`data glove n. A data input device or controller in the
`form of a glove fitted with sensors that convert movement
`of the hand and fingers into commands. See also virtual
`reality.
`
`datagram n. One packet, or unit, of information, along
`with relevant delivery information such as the destination
`address, that is sent through a packet-switching network.
`See also packet switching.
`
`data Independence n. The separation of data in a data-
`base from the programs that manipulate it. Data indepen-
`dence makes stored data as accessible as possible.
`
`data lntegrlty n. The accuracy of data and its conformity
`to its expected value, especially after being transmitted or
`processed.
`
`data Interchange format n. A format consisting of
`ASCII codes in which database, spreadsheet, and similar
`documents can be structured to facilitate their use by and
`transfer to other programs. Acronym: DIF. See also ASCII.
`data Item 71. See data element.
`
`data llbrary n. A cataloged collection of data files on disk
`or in another storage medium.
`
`data llnk n. A connection between any two devices
`capable of sending and receiving information, such as a
`
`
`
`150/05: Layer
`Application
`(highest level)
`
`Presentation
`
`Session
`
`Transport
`
`Network
`
`Data~|ink
`
`Physical
`
`ISO/OSI MODEL
`Focus
`
`Program-to-program transfer
`of information
`
`Text formatting and display, code
`conversion
`
`Establishing, maintaining. and
`coordinating communication
`
`Accurate delivery, service quality
`
`Transport routes, message
`handling and transfer
`Coding, addressing, and
`transmitting information
`Hardware connections
`
`Data-link layer on ISO/OSI reference model.
`
`data management n. The control of data from acquisi-
`tion and input through processing, output, and storage. In
`microcomputers, hardware manages data by gathering it,
`moving it, and following instructions to process it. The
`operating system manages the hardware and ensures that
`
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`data manipulation
`
`data sharing
`
`the parts of the system work in harmony so that data is
`stored safely and accurately. Application programs man—
`age data by receiving and processing input according to
`the user’s commands, and sending results to an output
`device or to disk storage. The user also is responsible for
`data management by acquiring data, labeling and organiz-
`ing disks, backing up data, archiving files, and removing
`unneeded material from the hard disk.
`
`data manlpulatlon n. The processing of data by means of
`programs that accept user commands, offer ways to handle
`data, and tell the hardware what to do with the data.
`
`data manlpulatlon language 11. In database manage-
`ment systems, a language that is used to insert data in,
`update, and query a database. Data manipulation lan-
`guages are often capable of performing mathematical and
`statistical calculations that facilitate generating reports.
`Acronym: DML. See also structured query language.
`data mart n. A scaled-down version of a data warehouse
`
`that is tailored to contain only information likely to be
`used by the target group. See also data warehouse.
`
`data medlum n. The physical material on which com-
`puter data is stored.
`
`data mlgratlon n. 1. The process of moving data from one
`repository or source, such as a database, to another, usually
`via automated scripts or programs. Often data migration
`involves transferring dam from one type of computer sys-
`tem to another. 2. In supercomputing applications, the pro-
`cess of storing large amounts of data off line while making
`them appear to be on line as disk-resident files.
`
`data mlnlng n. The process of identifying commercially
`useful patnerns, problems, or relationships in a database, a
`Web server, or other computer repository through the use
`of advanced statistical tools. Some Web sites use data
`
`mining to monitor the efficiency of site navigation and to
`determine changes in the Web site’s design based on how
`consumers are using the site.
`
`data model 11. A collection of related object types, opera-
`tors, and integrity rules that form the abstract entity sup-
`ported by a database management system (DBMS). Thus,
`one speaks of a relational DBMS, a network DBMS, and
`so on, depending on the type of data model a DBMS
`supports. In general, a DBMS supports only one data
`model as a practical rather than a theoretical restriction.
`
`data network It. A network designed for transferring
`data encoded as digital signals, as opposed to a voice net-
`work, which transmits analog signals.
`
`Data Over Cable Servlce Interface Speclflcatlon it
`See DOCSIS.
`
`data-overrun error n. An error that occurs when more
`
`data is being acquired than can be processed. See also bps.
`
`data packet 21. See packet.
`
`data path 11. The route that a signal follows as it travels
`through a computer network.
`
`data polnt 11. Any pair of numeric values plotted on a
`chart.
`
`data processlng n. 1. The general work performed by
`computers. 2. More specifically, the manipulation of data
`to transform it into some desired result. Acronym: DP.
`Also called: ADP, automatic data processing, EDP, elec-
`tronic data processing. See also centralized processing,
`decentralized processing, distributed processing.
`
`Data Processlng Management Assoclatlon 11. See
`DPMA.
`
`data projector n. A device, similar to a slide projector,
`that projects the video monitor output of a computer onto
`a screen.
`
`data protectlon n. The process of ensuring the preserva-
`tion, integrity, and reliability of data. See also data integrity.
`
`data rate n. The speed at which a circuit or communica-
`tions line can transfer information, usually measured in
`bits per second (bps).
`data record n. See recordl.
`
`data reductlon n. The process of converting raw data to
`a more useful form by scaling, smoothing, ordering, or
`other editing procedures.
`
`data segment n. The portion of memory or auxiliary
`storage that contains the data used by a program.
`Data Servlce Unlt n. See DDS.
`
`data set n. 1. A collection of related information made
`
`up of separate elements that can be treated as a unit in data
`handling. 2. In communications, a modem. See also
`modem.
`
`Data Set Ready 11. See DSR.
`
`data sharlng n. The use of a single file by more than one
`person or computer. Data sharing can be done by physi-
`cally transferring a file from one computer to another, or,
`more commonly, by networking and computer-to-computer
`communications.
`
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`data signal
`
`date dependency
`
`data slgnal n. The information transmitted over a line or
`circuit. It consists of binary digits and can include actual
`information or messages and other elements such as con-
`trol characters or error-checking codes.
`
`data slnk n. 1. Any recording medium where data can be
`stored until needed. 2. In communications, the portion of a
`Data Terminal Equipment (DTE) device that receives
`transmitted data.
`
`data source 11. 1. The originator of computer data, fre-
`quently an analog or digital data collection device. 2. In
`communications, the portion of a Data Terminal Equip-
`ment (DTE) device that sends data.
`
`data stream 11. An undifferentiated, byte-by-byte flow of
`data.
`
`data structure n. An organizational scheme, such as a
`record or array, that can be applied to data to facilitate
`interpreting the data or performing operations on it.
`
`data swltch n. A device in a computer system that routes
`incoming data to various locations.
`
`Data Termlnal Equlpment n. See DTE.
`
`Data Termlnal Ready n. See DTR.
`
`data traffic n. The exchange of electronic messages—
`control and data—across a network. Traffic capacity is
`measured in bandwidth; traffic speed is measured in bits
`per unit of time.
`data transfer 11. The movement of information from one
`
`location to another, either within a computer (as from a
`disk drive to memory), between a computer and an exter-
`nal device (as between a file server and a computer on a
`network), or between separate computers.
`data transfer rate 11. See data rate.
`
`data transmlsslon n. The electronic transfer of informa-
`
`tion from a sending device to a receiving device.
`
`data type it. In programming, a definition of a set of data
`that specifies the possible range of values of the set, the
`operations that can be performed on the values, and the
`way in which the values are stored in memory. Defining
`the data type allows a computer to manipulate the data
`appropriately. Data types are most often supported in
`high-level languages and often include types such as real,
`integer, floating point, character, Boolean, and pointer.
`How a language handles data typing is one of its major
`characteristics. See also cast, constant, enumerated data
`type, strong typing, type checking, user-defined data type,
`variable, weak typing.
`
`data valldatlon n. The process of testing the accuracy
`of data.
`
`data value It. The literal or interpreted meaning of a data
`item, such as an entry in a database, or a type, such as an
`integer, that can be used for a variable.
`
`data warehouse1 n. A database, frequently very large,
`that can access all of a company’s information. While the
`warehouse can be distributed over several computers and
`may contain several databases and information from
`numerous sources in a variety of formats, it should be
`accessible through a server. Thus, access to the warehouse
`is transparent to the user, who can use simple commands
`to retrieve and analyze all the information. The data ware-
`house also contains data about how the warehouse is orga-
`nized, where the information can be found, and any
`connections between data. Frequently used for decision
`support within an organization, the data warehouse also
`allows the organization to organize its data, coordinate
`updates, and see relationships between information gath-
`ered from different parts of the organization. See also
`database, decision support system, server (definition 1),
`transparent (definition 1).
`
`data warehouse2 vb. To acquire, collect, manage, and
`disseminate information gathered from various sources into
`a single location; or to implement an informational database
`used to store sharable data. Data warehousing is a four-step
`process: gathering data; managing the data in a centralized
`location; providing access to the data along with tools for
`interpreting, analyzing, and reporting on the data; and pro-
`ducing reports on the data to be used for decision making.
`See also downflow, inflow, metaflow, upflow.
`
`date and tlme stamp n. See time stamp.
`
`date counter overflow n. A problem that may occur in
`systems or programs when the value in a date variable
`exceeds allowable values. A date counter overflow can
`
`occur when an incremental date produces a number that the
`system interprets as zero or a negative number. This is
`likely to cause the system or program to post an error mes-
`sage in turn or to revert to the original starting point.
`Although this was largely considered a Year 2000 problem,
`such an error is not necessarily confined to the year 2000.
`
`date dependency n. In terms of the Year 2000 problem,
`the need many programs have for date-related input or
`output data and the way dates are represented in that data.
`This dependency affects whether the program can run cor-
`rectly when the turn of the century is reached.
`
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`

`

`date expansion
`
`DCD
`
`date expanslon n. A method of dealing with programs
`with Year 2000 problems that entails changing data, data
`descriptions, and (if necessary) program logic that pertains
`to dates by expanding date fields from two digits to four
`digits—for example, from DDMMYY to DDMMYYYY.
`date format it The manner in which dates are formatted
`
`in a computer system or program. While some organiza-
`tions require that the same format be used throughout their
`systems and programs, many organizations have not,
`which can make tracking down potential date problems,
`such as the Year 2000 problem, difficult. In addition, date
`formats can vary Widely from organization to organiza-
`tion, although many have opted to standardize on formats
`specified in ANSI X3.30-1997 or ISOS601:1988.
`
`date horlzon n. A period of time that a program uses to
`determine the beginning or ending point in perfonning its
`functions. A program that tracks inventory may have one
`date horizon that trails the current date by two months (a
`trailing date horizon) to process returned merchandise and
`another that precedes it by another two months (a leading
`date horizon) for planning purposes. If the program logic
`doesn’t account for any date horizons it may have, for
`example, if the year was 1999, the program could experi-
`ence Year 2000 problems when the leading date horizon
`enters January 1, 2000. See also event horizon.
`
`date-ln-key problem It. A potential problem in computer
`systems that depend on indexed files using a two-digit
`date as part of the key, such as certain databases. If the
`files need to be in chronological order, the files beginning
`with the year 2000 will be out of sequenceifor example,
`(1 9)99 would be interpreted as more recent than (20)00.
`date rollover it. See Year 2000 rollover.
`
`date stamp n. See time stamp.
`
`date stamplng n. A software feature that automatically
`inserts the current date into a document.
`
`datum n. Singular of data; a single item of information.
`See also data.
`
`daughterboard n. A circuit board that attaches to
`another, such as the main system board (motherboard), to
`add extra capabilities. See also motherboard.
`
`DAV connector 11. See digital audio/video connector.
`
`day-of-the-week problem n. A reference to an inaccu-
`racy that may occur after the Year 2000 in computers that
`
`calculate the day of the week based on the last two digits
`of the year, assuming that the dates they calculate fall in
`the 1900s. Because January 1, 1900 was a Monday, but
`January 1, 2000 will be a Saturday, those computers may
`not be able to correctly determine the day of the week.
`This is particularly problematic in computers that regulate
`timed systems based on the business week, such as a door
`or vault that unlocks during business hours.
`DB 11. See database.
`
`dB 11. See decibel.
`
`DBA It. See database administrator.
`
`DB connector n. Any of various connectors that facilitate
`parallel input and output. The initials DB (for data bus) are
`followed by a number that indicates the number of lines
`(wires) within the connector. For example, a DB—9 con-
`nector has nine pins and supports up to nine lines, each of
`which can connect to a pin on the connector.
`.dbf n. A file extension for a dBASE database file.
`
`DBMS It. See database management system.
`DBS 71. See direct broadcast satellite.
`
`deML n. Acronym for database XML. A native XML
`database server designed to manage large collections of
`XML documents. deML may be embedded in custom
`applications or run as a stand-alone database.
`Dc n. See direct current.
`
`DCA n. 1. Acronym for Document Content Architecture.
`A formatting guideline used in IBM’s Systems Network
`Architecture (SNA) that enables the exchange of text-only
`documents between differing types of computers. DCA
`provides for two types of document formatting: Revisable-
`Form—Text DCA (RFTDCA), which allows for modifica-
`tion of formatting, and Final-Form—Text DCA (FFTDCA),
`which cannot be modified. See also DIA, SNA.
`2. Acronym for Directory Client Agent. See DUA.
`
`DCD n. 1. Acronym for Data Carrier Detected. A signal in
`serial communications that is sent from a modem to its
`
`computer to indicate that the modem is ready for transmit-
`ting. Also called: RLSD. See also RS—232-C standard.
`2. Acronym for Document Content Description. A specifica—
`tion governing the rules for defining the structure and con-
`tent of XML documents. The specification was created by
`IBM and Microsoft in 1998 and was submitted to the World
`
`Wide Web Consortium for approval. See also XML.
`
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`DCE
`
`DDS
`
`DCE n. 1. Acronym for Data Communications Equip-
`ment. The term used in RS—232 and X25 specifications
`for a device, such as a modem, that provides another
`device (known as the Data Terminal Equipment or DTE)
`with access to a communications line. A DCE is an inter-
`
`mediary device that often transforms input from a DTE
`before sending it to a recipient. See also RS-232-C stan-
`dard, X series. Compare DTE. 2. See Distributed Com-
`puting Environment.
`D channel n. Short for data channel. In the ISDN com-
`
`munications architecture, the channel dedicated to carry-
`ing control signals, such as packet-switching infomlation;
`and user—related data, such as phone numbers. The basic
`ISDN connection, called the Basic Rate Interface (BRI), is
`composed of two B (bearer) channels, which carry as
`much as 64 Kbps of actual data each, and one D channel,
`which transmits at either 16 Kbps or 64 Kbps. The faster
`Primary Rate Interface (PRI) is composed of one 64-Kbps
`D channel and either 23 or 30 B channels operating at 64
`Kbps. See also B channel, BRI, ISDN.
`
`DCOM n. Acronym for Distributed Component Object
`Model. The version of Microsoft’s Component Object
`Model (COM) specification that stipulates how components
`communicate over Windows-based networks. It permits the
`distribution of different components for a single application
`across two or more networked computers, running an appli—
`cation distributed across a network so that the distribution
`
`of components is not apparent to the user, and remotely dis-
`playing an application. Also called: Distributed COM. See
`also COM (definition 2), component (definition 2).
`
`DOS n. Acronym for Desktop Color Separation. The pri-
`mary fomiat for preparing digital publication text and
`graphics for printing. DCS layouts consist of five files, one
`for each of the CMYK colors, and a master file which,
`includes the display version of the page and information
`on the other four files. See also OPI.
`
`DCTL It. See direct-coupled transistor logic.
`
`DDBMS n. See distributed database management system.
`
`DDC n. Acronym for Display Data Channel. A VESA
`standard that allows software control of graphical com-
`puter monitors. Under DDC, monitor characteristics are
`provided to the graphics subsystem, which uses the data to
`configure the display and provide a bidirectional commu-
`nication channel between the monitor and computer. Also
`called: VESA DDC. See also VESAZ.
`
`DDCP n. See direct digital color proof.
`
`DDE n. Acronym for Dynamic Data Exchange. An inter-
`prooess communication method featured in Microsoft Win-
`dows and 08/2. DDE allows two or more programs that are
`running simultaneously to exchange data and commands. In
`Windows 3.1, DDE was largely supplanted by OLE, which
`is an extension of DDE. In Windows 95 and Windows NT,
`OLE and ActiveX are more commonly used. See also
`ActiveX, interprooess communication, OLE.
`
`DDK n. Acronym for Driver Development Kit. A set of
`tools used to create software that enables an operating sys-
`tem to work with hardware devices. With a DDK, a soft-
`ware developer can build drivers to support network,
`storage, print, sound, video, input, and other devices. Also
`called: Device Driver Kit, Device Driver Developer Kit.
`See also driver.
`
`DDL n. See data definition language.
`
`D005 11. Acronym for distributed denial of service attack.
`A form of denial of service attack (DoS) originating from
`several computers that seeks to disrupt Web access by
`overwhelming a target with connection requests that can-
`not be completed. A DDoS attack involves cracking into a
`number of computers and planting programs that lie dor-
`mant until sent a signal to attack. At that point the comput-
`ers send a steady stream of data packets to the targeted
`Web site, overwhelming the ability of the Web server to
`respond. Because the attack is coming from many comput-
`ers, security features that might otherwise recognize the
`attack and stop accepting data packets from a single
`source are unable to shut down connections to all the
`
`attackers. See also DoS, packet, zombie.
`
`DDR SDRAM n. Short for Double Data Rate Synchro-
`nous Dynamic RAM (SDRAM). A form of SDRAM that
`essentially doubles memory throughput to 200 megahertz
`or better. DDR SDRAM gets a boost in data transfer rates
`by producing output on both the rising and falling of the
`system clock—that is, twice for each clock cycle. See
`also SDRAM.
`
`DDS n. Acronym for digital data service, a dedicated
`communications line that provides transmission at speeds
`up to 56 Kbps. DDS lines use a device known as a CSU/
`DSU rather than a modem for connecting two networks.
`The CSU, or Channel Service Unit, connects the network
`to the transmission line; the DSU, or Data Service Unit,
`converts data for transmission by the CSU and controls
`data flow.
`
`147
`
`PATENT OWNER DIRECTSTREAM, LLC
`EX. 2064, p. 157
`
`PATENT OWNER DIRECTSTREAM, LLC
`EX. 2064, p. 157
`
`

`

`dead code
`
`decibel
`
`dead code n. Program code that never gets executed,
`possibly because the programmer has eliminated all refer-
`ences to it, or possibly because the program is written in
`such a way that the instruction(s) will never be needed—
`for example, an ELSE statement would never be needed in
`an IF condition that always proved to be true. Dead code
`can slow program execution and increase the size of the
`program in memory. Also called: grunge, software rot.
`
`dead halt n. A machine stop with no hope of recovery by
`either the program or the operating system. The only
`choice after a dead halt is to reboot. Also called: drop-
`dead halt. See also hang. Compare reboot.
`
`dead key It A key used with another key to create an
`accented character. When pressed, a dead key produces no
`visible character (hence its name) but indicates that the
`accent mark it represents is to be combined with the next
`key pressed. See also key (definition 1).
`
`dead-letter box n. In e-mail or message systems, a file to
`which undeliverable messages are sent.
`
`deadlock n. 1. A situation that occurs when two pro-
`grams or devices are each waiting for a response from the
`other before continuing. Also called: deadly embrace.
`2. In operating systems, a situation in which two or more
`processes are prevented from continui