| Glossary of Terms |
| All Numbers 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 |
D
daisychain port
A set of devices connected to each other in a series.
data compression
Compacting information for efficient storage.
data dictionary
An on-line reference facility recording all components of a software system - often a relational database. It covers names, characteristics, relationships and structure. Components may be files or tables, fields or variables—or even complete databases. Through comprehensive characterization of each component (specification of what it is), the data dictionary provides a valid basis for system development and global reporting.
data flow analysis
Establishing the order in which a program must execute determined by the dependencies between different data. For example, if you wanted to process a payroll for a new tax month, you would have to update the tax month number in the tax month field that the payroll program will check before it could calculate tax due by an employee.
data hierarchy
The set of levels in which data is organized (e.g., in descending order of levels: files, records, fields; or: databases, tables, fields.)
data integrity
Insuring that data is not corrupted or changed by anything except processes initiated by users.
data mining
Analysis of data in a Database using tools which look for trends or anomalies (irregularities).
data model
With reference to a database, a description of data structures (field size, type etc.) and operations to manipulate and validate them.
data server
A system or unit providing information on a network or the Internet.
data structure
The way data is organized, its field attributes and its relationships to other data in databases, tables and files.
data transfer rate
The speed of the movement of information from one location to another.
data transmission
Moving data, usually through a communication network.
data warehouse
Analysis of the vast amount of historical corporate data can provide the vital information regarding business trends and structures needed to refine a corporation's deliverables (products or services to customers). Data Warehouse Systems provide a 'multi-dimensional' view that lends itself to quick adhoc queries on large volumes of data on a read-only basis. Data Warehouse software is optimized for this purpose but requires large and powerful hardware for its effective use, a point of great interest to Hardware Vendors.
database server
A server that holds and manages a database of information in a client/server network.
daughter board
An additional board or 'card' inserted into an expansion slot in the motherboard of a PC to introduce more functionality, enhance performance or establish a link to a network or peripheral device.
debug
With software, to detect, locate, and correct logical or syntactical errors in a computer program. With hardware, to detect, locate and correct a malfunction or to fix an inoperable system.
debugging
In system testing, the process of locating and removing coding mistakes (bugs) in a computer program.
decision support system
Software used to aid management decisions.
default
A word used as both noun and verb in reference to the choice made by a program when the user does not specify an alternative. Defaults are built into programs if some value or option needs to be assumed in order for the program to function.
delimiter
A character that defines the start and end of field, but is not part of that field. Commas are often used, as in comma-separated files.
desktop publishing
The creation and manipulation of words and images via a computer screen for the production of documents.
destination address
On a network, the unique identifier of where a signal is being sent to; the precise location code of the receipt point for a transmitted message.
device
A generic term for a computer subsystem. Printers, serial ports, and disk drives are often referred to as devices; such subsystems frequently require their own controlling software, called device drivers.
See device driver
device driver
A software component that permits a computer system to communicate with a device. A printer driver is a device driver that translates computer data into a form understood by the intended printer.
diagnostic LED
A small light that is used for troubleshooting.
Diagonal Linear Measurement
"Office" screen size is the diagonal measure of the CRT before its mounted in the monitor cabinet. Some monitor CRT category are 14", 15", 17", 20", and 21".
digital
A signal that is either on or off with nothing in between. This is how computers store data. This is not usable with phone lines so a modem is needed.
digital camera
A camera that stores images electronically instead of on film.
DIP
(See "Dual In-Line Package (DIP)".)
directory
A catalog for filenames and other directories stored on a disk; a way of organizing and grouping the files on a disk so that the user is not overwhelmed by a long list of files. In the Macintosh operating system, directories are called folders.
disk
A 3.5" or 5.25" removable storage device; in most computers, the primary means of storing data on a permanent or semi-permanent basis.
disk drive
An electromechanical device that reads from and writes to disks; floppy-disk and hard-disk drives are in common use; floppy disk drives are designed to accept removable disks in either 5.25-inch or 3.5-inch formats; hard-disk drives are faster, high-capacity storage units that are completely enclosed in a protective case.
Disk Operating System (DOS)
The 16-bit operating system common to IBM-compatible PCs. Also called MS-DOS (MS standing for Microsoft, the authors of DOS).
diskette
A floppy disk.
display
Show or lay out something for examination. In relation to computers, to bring something onto a screen so that a user can view it. Also, the part of a computer (the screen) that provides the interactive visual information for the user.
distributed computing
Similar to distributed processing, but in a client/server context.
distributed processing
In control systems, networks, or telecommunications: a system in which each
computer in a network performs processing while a network controller manages communications between them.
document image processing
The storage, retrieval and manipulation of whole documents. Usually associated with optical disk technology.
DOS
(See "Disk Operating System (DOS)".)
dot pitch
The distance between dots in printers. In video display, it is a measure of clarity.
dot-matrix printer
A type of printer that forms characters with a series of dots. The quality of the output from a dot-matrix printer depends largely on the number of dots in the matrix, which might be low enough to show individual dots or might be high enough to approach the look of fully-formed characters. Dot-matrix printers are often categorized by the number of pins in the print head—typically 9, 18 or 24. The general rule is, the higher the number of pins, the better the print quality.
double density
A method of packing a disk with more data than single density allows; about 713K compared with 360K.
download
Move data from a central storage area into memory or local storage on the client for subsequent processing. Transfer a file or data from one network node to another. It generally refers to transferring a file from a "big" node, such as a minicomputer, to a "small" node, such as a terminal server or printer.
drag
In Microsoft Windows, using the mouse, place the arrow-shaped cursor onto the screen object to be moved. Hold down the left mousebutton, and at the same time, move the mouse until the object is where you want it.
Drag and Drop
(See "Drag".)
DRAM
(See "Dynamic RAM (DRAM)".)
drill down
Going from one level of information to a lower, more detailed level of information.
drivers
Set of files that controls or regulates a piece of hardware.
drop-down menu
A menu box which appears to users when they select certain options. Users must then select a further option from the drop-down menu.
drum
A rotating cylinder that is used in some printers as a storage medium for data.
Dual In-Line Package (DIP)
The plastic or ceramic carrier device that houses a chip or other electrical devices.
dumb terminal
An input/output device used in terminal/host systems, comprising a screen and keyboard. Capable of generating characters for display on the screen, but with no other built-in processing power.
duplex
A standard for data transmission; full-duplex channels carry data both ways at the same time; half-duplex channels carry data in only one direction at a time.
DVD-ROM
A high-density compact disk system using a more focused laser then the conventional CD-ROM with storage capacities of up to 9.4 GB on a double-sided disk.
Dvorak keyboard
A keyboard layout developed by August Dvorak and William L. Dealey in 1936 as an alternative to the overwhelmingly popular QWERTY keyboard. The Dvorak keyboard was designed to speed typing by placing the characters on the keyboard for easiest access to the most frequently typed letters. In addition, pairs of letters that often occur sequentially were separated so that the hands could alternate them.
Dynamic RAM (DRAM)
A chip comprising the main memory in most desktop systems. DRAMs store information in integrated circuits that contain capacitors. Because capacitors lose their charge over time, DRAM boards must include logic to "refresh" the RAM chips continuously. While DRAM is being refreshed, it cannot be read by the processor; if the processor must read the RAM while it is being refreshed, one or more wait states occur. Because their internal circuitry is simple, DRAMs are more commonly used than static RAMs, even though they are slower. A dynamic RAM can hold approximately four times as much data as a static RAM chip of the same complexity.
Several glossary definitions supplied and copyrighted by:
Microsoft® Corporation. To order the Microsoft Press Computer Dictionary, call Microsoft Press at 800-MSPRESS.
MDA Computing Ltd. For MDA Computing�s complete glossary of terms, go to www.mdagroup.com.
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