IBM Skip to main content
     Home  |  Products & services  |  Support & downloads  |  My account
 Select a country
IBM Archives
· Exhibits
· Reference
· Documents
· Multimedia
· Links
Using the Archives
Advanced Search


Reference / Glossary

IBM Archives
glossary entries for Aglossary entries for Bglossary entries for Cglossary entries for Dglossary entries for Eglossary entries for Fglossary entries for Gglossary entries for Hglossary entries for Iglossary entries for Jglossary entries for Kglossary entries for Lglossary entries for Mglossary entries for Nglossary entries for Oglossary entries for Pglossary entries for Qglossary entries for R
glossary entries for Sglossary entries for Tglossary entries for Uglossary entries for Vglossary entries for Wglossary entries for Xglossary entries for Yglossary entries for Zglossary entries for 0glossary entries for 1glossary entries for 2glossary entries for 3glossary entries for 4glossary entries for 5glossary entries for 6glossary entries for 7glossary entries for 8glossary entries for 9
Cross References
DASD See direct access storage device.
data 1. n A re-interpretable representation of information in a formalized manner suitable for communication, interpretation, or processing. Operations can be performed upon data by humans or by automatic means. 2. n. Any representations such as characters or analog quantities to which meaning is or might be assigned. 3. n. A representation of facts or instructions in a form suitable for communication, interpretation, or processing by human or automatic means.
data channel See input/output channel.
data communication 1. n. Transfer of data among functional units by means of data transmission according to a protocol. 2. n. The transmission, reception, and validation of data.
data compression See compression.
data dictionary n. A centralized repository of information about data such as meaning, relationships to other data, origin, usage, and format. It assists management, database administrators, system analysts, and application programmers in planning, controlling, and evaluating the collection, storage, and use of data.
data encrypting key n. A key used to encipher, decipher, or authenticate data.
Data Encryption Standard (DES) n. In computer security, the National Institute of Standards and Technology (NIST) Data Encryption Standard, adopted by the U.S. government as Federal Information Processing Standard (FIPS) Publication 46, which allows only hardware implementations of the data encryption algorithm.
data modeling n. A structured set of techniques for defining and recording business information requirements. It is a depiction of the user's view of the data needs of the organization in a consistent and rigorous fashion. The data model eventually serves as the basis for translation to computer system databases.
data network n. An arrangement of data circuits and switching facilities for establishing connections between data terminal equipment.
data store n. A place (such as a database system, file, or directory) where data is stored.
data stream 1. n. All information (data and control commands) sent over a data link usually in a single read or write operation. 2. n. A continuous stream of data elements being transmitted, or intended for transmission, in character or binary-digit form, using a defined format.
data transfer rate n. The average number of bits, characters, or blocks per unit time passing between corresponding equipment in a data transmission system. (Notes: 1. The rate is expressed in bits, characters, or blocks per second, minute, or hour. 2. Corresponding equipment should be indicated; for example, modems, intermediate equipment, or source and sink. )
database 1. n. A collection of data with a given structure for accepting, storing, and providing, on demand, data for multiple users. 2. n. A collection of interrelated data organized according to a database schema to serve one or more applications. 3. n. A collection of data fundamental to a system. 4. n. A collection of data fundamental to an enterprise.
DATABASE 2 n. Obsolete term for DB2.
database administrator n. A person who is responsible for a database system, particularly for defining the rules by which data is stored and accessed. Usually, the database administrator is also responsible for database integrity, security, performance, and recovery.
DB2 n. An IBM relational database management system that is available as a licensed program on several operating systems. Programmers and users of DB2 can create, access, modify, and delete data in relational tables using a variety of interfaces.
deactivate v. To take a resource of a node out of service, rendering it inoperable, or to place it in a state in which it cannot perform the functions for which it was designed.
decryption n. In computer security, the process of transforming encoded text or ciphertext into plaintext.
dedicated channel n. A channel that is not switched.
dedicated circuit n. A circuit that is not switched.
dedicated server n. A processor on a network that functions only as a server, not as a requester and a server.
deep computing n. Ultrafast computing that is combined with sophisticated analytical software to enable organizations to analyze, find patterns in, and take action on the data that they have gathered.
defragmentation n. The process of running a software utility to rewrite fragmented data to contiguous sectors of a computer storage medium to improve access and retrieval time.
delete n. A choice that removes a selected object. The space it occupied is usually filled by the remaining object or objects in the window.
delta 1. n. A list of changes (e.g., the differences between two programs). 2. n. A wedge-shaped gap, especially one between two lines on a graph, as when one line represents the target and the other achievement-to-date (as in: "That's a huge delta!"). 3. v. To arrive at a result from some known base, particularly by applying a percentage increase to all data (as in: "We'll just delta off last year's plan.").
demo 1. n. A demonstration of hardware or software to senior management or customers; provides the ideal conditions for awakening dormant and unsuspected bugs. 2. v. To demonstrate.
dependency n. A minor exposure.
desktop n. A graphical user interface (GUI) that enables a user to interact with and perform operations on a computer system.
device 1. n. A mechanical, electrical, or electronic contrivance with a specific purpose. 2. n. In the AIX operating system, a valuator, button, or the keyboard. Buttons have values of 0 or 1 (up or down); valuators return values in a range, and the keyboard returns ASCII values
device driver 1. n. A file that contains the code needed to use an attached device. 2. n. A program that enables a computer to communicate with a specific peripheral device; for example, a printer, a videodisc player, or a CD-ROM drive. 3. n. A collection of subroutines that control the interface between I/O device adapters and the processor.
dialog 1. n. The interaction between a user and a computer. 2. n. In an interactive system, a series of related inquiries and responses similar to a conversation between two people.
dialog box 1. n. In Common User Access (CUA) architecture, a movable window, fixed in size, containing controls that a user uses to provide information required by an application so that it can continue to process a user request. This is a programmer term; the user term is pop-up window. 2. n. In OSF/Motif, a collection of data fields and buttons for setting controls, selecting from lists, choosing from mutually exclusive options, entering data, and presenting the user with messages.
dialog pop-up n. In Common User Access (CUA) architecture, a bordered area of the screen that is directly associated with a panel in a primary window. Through a dialog pop-up, a user provides information needed to complete a dialog in the underlying panel.
dial-up adj. Pertaining to a network connection that is established by dialing a telephone number.
digital 1. adj. Pertaining to data that consist of digits. 2. adj. Pertaining to data in the form of digits.
digital signature n. In e-commerce, data that is appended to, or is a cryptographic transformation of, a data unit and that enables the recipient of the data unit to verify the source and integrity of the unit and to recognize potential forgery.
direct access storage device n. (DASD). A mass storage medium on which a computer stores data.
directory 1. n. In a hierarchical file system, a container for files or other directories. See path. 2. n. In an APPN node, a database that lists names of resources (in particular, logical units) and records the CP name of the node where each resource is located. See distributed directory database and local directory database. 3. n. In VM, a Control Program (CP) disk file that defines each virtual machine's typical configuration.
disable v. To make nonfunctional.
disabled 1. adj. Pertaining to a state of a processing unit that prevents the occurrence of certain types of interruptions. 2. adj. Pertaining to the state in which a transmission control unit or audio response unit cannot accept incoming calls on a line.
disk drive n. A diskette drive or a hard disk drive (as opposed to a CD-ROM drive).
disk operating system n. An operating system for computer systems that use disks and diskettes for auxiliary storage of programs and data.
display 1. n. A visual presentation of data. 2. v. To present data visually. 3. n. Obsolete term for panel.
display panel n. In computer graphics, a predefined display image that defines the locations and characteristics of display fields on a display surface.
display station n. An input/output device containing a display screen and an attached keyboard that allows a user to send information to or receive information from the system. See terminal and workstation.
distributed print system n. A computer system that interchanges print data across different computing environments, thereby allowing data to be printed on a system other than the one at which the print request was generated. For example, in host-to-LAN distributed printing, data that resides on the host is printed on printers attached to a local area network (LAN).
distributed processing n. Processing that takes place across two or more linked systems.
docked 1. adj. Pertaining to a mobile computer that is connected to its docking station. 2. adj. Pertaining to an element of a Microsoft Windows interface (such as the application desktop toolbar) that is aligned with and attached to the edge of another element of the interface, such as a window or a pane.
docking station n. A hardware device that enables a mobile computer to function as a desktop computer. For example, a peripheral device (such as an external monitor, an external modem, or external speakers) can be connected to a mobile computer via its docking station. Also, a docking station may contain devices (such as CD-ROM drives) that the mobile computer does not have; but when the mobile computer is docked, it can use all components and features of the docking station.
document root directory n. The primary directory in which a Web server stores accessible documents. When the server receives requests that do not point to a specific directory, it tries to serve the requests from this directory.
document type n. The type of data in a particular Printing Systems Manager (PSM) document. For example, a print file document contains only printable data, and a print resource document contains only data such as fonts or form definitions that are not printable.
domain 1. n. That part of a computer network in which the data processing resources are under common control. 2. n. In Open Systems Interconnection (OSI), a part of a distributed system or a set of managed objects to which a common policy applies. 3. n. In a database, all the possible values of an attribute or a data element.
domain name n. In the Internet suite of protocols, a name of a host system. A domain name consists of a sequence of subnames separated by a delimiter character. For example, if the fully qualified domain name (FQDN) of a host system is, each of the following is a domain name:;;
domain name server n. In the Internet suite of protocols, a server that responds to queries from clients for name-to-address and address-to-name mappings as well as for other information.
Domain Name System n. In the Internet suite of protocols, the distributed database system used to map domain names to IP addresses.
domain search n. A search initiated by a network node to all its authorized client APPN end nodes (that allow themselves to be searched) when it receives a search request for which it has no entry in its database.
DOS n. Disk Operating System (see).
dotted decimal notation n. The syntactical representation of an IP address. The 4 bytes of the address are written as four decimal numbers separated by periods (dots), for example,
dotted to 1. adj. Having a managerial relationship that cannot be described in a hierarchical tree. Contemporary matrixed organizations have numerous such relationships.
double-byte character session n. A display station operating session that uses double-byte character data for the system to communicate with the operator.
double-byte character set n. A set of characters in which each character is represented by 2 bytes. Languages such as Japanese, Chinese, and Korean, which contain more symbols than can be represented by 256 code points, require double-byte character sets. Because each character requires 2 bytes, the typing, display, and printing of DBCS characters requires hardware and programs that support DBCS.
double-click v. To press and release a button on a pointing device twice while a pointer is within the limits that the user has specified for the operating environment.
doubleword n. A contiguous sequence of bits or characters that comprises two computer words and is capable of being addressed as a unit.
down adj. Not working; the opposite of up (see). Crashed.
download 1 v. To transfer programs or data from a computer to a connected device, typically a personal computer. 2. v. To transfer data from a computer to a connected device, such as a workstation or microcomputer.
downstream 1. adj. In a network, pertaining to the direction to which data flows. 2. adj. In a hierarchical network structure, pertaining to the location of a network entity that is lower in the hierarchy. For example, a client is downstream from a server.
downtime n. The length of time that a system is not available to users.
drag v. To use a pointing device to move an object. For example, a user can drag a window border to make the window larger.
drag and drop v. To directly manipulate an object by moving it and placing it somewhere else using a pointing device (such as a mouse (see)).
drive 1. n. A peripheral device, especially one that has addressed storage media. 2. n. The mechanism used to seek, read, and write information on a storage medium. 3. v. To push a project along in spite of many obstacles and objections.
drive designation n. A letter (from A to Z) that an operating system assigns to a disk, a partition, or a network directory to give the system a unique way to refer to the resource.
driver See device driver.
drop-dead date n. A deadline by which certain events must have occurred if irretrievable loss of honor is to be avoided.
dump 1. n. A collection or recitation of all available information about a problem (as in: "I need a quick dump on that issue."). 2. v. To record, at a particular instant, the contents of all or part of one storage device in another storage device.. 3. n. Data that has been dumped. 4. v. To copy data in a readable format from main or auxiliary storage onto an external medium such as tape, diskette, or printer. 5. v. To copy the contents of all or part of virtual storage .
duplex 1. adj. Pertaining to communication in which data can be sent and received at the same time. Contrast with half-duplex. 2. adj. Pertaining to printing on both sides of a sheet of paper such that the bottom of the printed image on one side of the paper is juxtaposed against the bottom of the printed image on the other side of the paper. Contrast with simplex and tumble.
dynamic partition n. A partition configured at the time of program execution according to the storage requirements of the application program or program to which the partition is allocated.
  About IBM  |  Privacy  |  Legal  |  Contact