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Technology Terminologies (A to Z)

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

Data Link Layer

Layer two of the OSI reference model. It controls the transfer of information between nodes over the Physical Layer.

data

Information suitable for communication, interpretation or processing by a computer.

data communications

The collection and redistribution of data through communications channels, often including operations such as coding, decoding and validation.

data entry

The entry of data into a computer or onto a computer-readable medium by an operator from a single data device, such as a card reader or keyboard.

data processing

The systematic performance of operations upon data, for example, handling, merging, sorting and computing.

database

A collection of interrelated data values that may be integrated permanently into a single connected structure or integrated temporarily for each interrogation, known as a query. In its most technical sense, database implies that any of the data may be used as a key for specific queries. In more common usage it means any accessible collection of information and that only a limited set of data values may be used to specify queries.

database management system

A systematic approach to storing, updating, securing and retrieving information stored as data items, usually in the form of records in one or more files.

DBMS

DataBase Management System.

debug

To detect, trace and eliminate errors in computer programs.

default

A software function or operation which occurs automatically unless the user specifies something else.

delete key

Personal computers normally allow deletion of typing mistakes by either the backspace key or the Del key. Users must either specify which of these keys they wish to use, or set their communication software to match whichever key the network expects.

dial-up

To connect to a computer by calling it on the telephone.

dictionary file

A special form of machine-readable codebook that contains information about the structure of a datafile and the locations and, often, the names of variables variables in the datafile. Typically, you use a dictionary file and a datafile together with statistical software; the statistical software uses the dictionary so that you may specify variables by name, rather than having to specify their locations in the file.

digital

Used in computerese to describe information that can be represented by a collection of bits.

direct access

The ability to read or write data directly from or to any location on a storage device without having to refer to data that was previously written. Files written with direct access do not have to be read sequentially starting at the beginning.

directory

A logical container of files and other directories; synonymous with folder. Typically implemented as a file that contains pointers (directions) to files or other directories.

disk or diskette

A small, flat, either rigid or floppy magnetic disk for storing data permanently. Magnetic medium for data storage. Either "floppy" diskettes (720K to 1.4 megabytes), or "hard" disks (usually 20 megabytes or more).

display

A device that enables information, either textual or pictorial, to be seen but not permanently recorded. The most widely used kind is the cathode-ray tube.

distributed

Processing resides in more than one computer in a network.

distributed application

Application designed so that components run on different - but cooperating - systems on a network.

distributed database

The data resides in more than one physical database in a network. Access to the data involves more than one database server. Clients may have to connect to more than one server directly and integrate the data they receive according to the applications needs.

distributed file system

Allows files on remote nodes of a network to appear locally connected.

document

A medium and the data recorded on it for human use; for example, a report sheet or book. By extension, any record that has permanence and that can be read by human or machine.

documentation

A collection of organized documents or the information recorded in documents. Also instructional material specifying the inputs, operations and outputs of a computer program or system.

DOS

Disk Operating System. A Microsoft program that controls a computers transfer of data to and from a hard or floppy disk. DOS generally refers to the operating systems for the IBM PCs and their clones. Also the name of an old operating system on IBM mainframes.

dot-matrix printer

A printer that creates each character from an array of dots. The dots are formed by pins striking a ribbon against the paper, one pin for each dot position. The printer may be a serial printer (printing one character at a time) or a line printer.

down

A computer is down when it is not running. It may be shut down for maintenance, hardware failure, or failure of the operating system or user program.

download

The transfer of information from a remote computer system to the users system. Opposite of upload.

downtime

The time interval during which equipment is nonfunctional.

drag and drop

A protocol supported by OPEN LOOK and Macintosh System 7 that allows a user to specify the input file to an application by dragging the icon representing the file onto the applications icon and dropping it there. OPEN LOOK also recognizes dragging the icon into the applications input panel. For example, dragging a files icon into the printool application causes it to be printed.

drive

A generic term used to identify the equipment that serves as a player or recorder for a storage medium.

dump

A printed representation of the contents of a computer storage device, usually main memory, backed-up when a system crash or other failure has occurred. As a verb, refers to a large amount of data.

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