Glossary of Computer Terms—D
D
DAISY-WHEEL
PRINTER: An impact printer that uses a print element shaped like a flat disk or
large thimble to form the alphanumeric and punctuation marks that are part of
its print element. Unlike dot-matrix, ink-jet, and laser printers, daisy-wheel
printers can not print graphics. See LETTER-QUALITY PRINTER.
DATABASE: A collection of
similar information stored in a file, such as a database of addresses. This
information may be created and stored in a database management system (DBMS).
DATA: Anything that
is recorded or used for processing. The stuff that transfers between computers
needed a name — data seemed good.
DATA RATE: Speed that
information moves from one item to another. This is usually in the form of
bits.
DATA-BASE
MANAGEMENT SYSTEM (DBMS): A software program that controls and
supervises the updating, editing, and execution of items from multiple files in
a data base environment.
DDR: Stands for
“Double Data Rate.” A type of advanced SDRAM designed to deliver data at a
double rate of speed for a given clock frequency.
DEBUG: The process of
detecting, locating, and correcting a problem in a software program or
hardware.
DECODER: A software,
hardware or circuit that is designed to translate a coded or scrambled signal
in to a readable form. A common use for this is by cable companies that
scramble a signal until a subscriber becomes authorized to view the signal. The
cable company then decodes the signal in to a viewable form.
DECRYPTION:This is a
process of converting information in to a readable form that has been encrypted
by the use of an encryption algorithm. A common use could be that a person
would like to protect sensitive data that resides on their computer system, so
they would use an encryption software to scramble the information. The same
software that scrambles the information would be the only authorized entity to
decrypt the information. This software could be made available to any
authorized person for decryption purposes at other locations.
DECREMENT: The reduction
of the numerical contents of a counter. A decrement of 1 is usually assumed,
unless otherwise specified. It is the complementary operation of INCREMENT.
DEFAULT: The pre-defined
configuration of a system or an application. In most programs, the defaults can
be changed to reflect personal preferences.
DESKTOP: The main
directory of the user interface. Desktops usually contain icons that represent
links to the hard drive, a network (if there is one), and a trash or recycling
can for files to be deleted. It can also display icons of frequently used
applications, as requested by the user.
DESKTOP
PUBLISHING: The production of publication-quality documents
using a personal computer in combination with text, graphics, and page layout
programs.
DEVICE: In a computer
system, this term refers to a unit of processing equipment external to the CPU.
It is sometimes synonymous with the term PERIPHERAL.
DEDICATED LINE: This is a phone
line meant specifically for one thing, like being attached to a computer.
DEMODULATION: This is the
process of converting analog information (like over phone lines) into digital
information (like in a computer). See “Modem” for more.
DIAL-UP LINE: This is a
telephone line that is connected to a server. When it is called, tones are
exchanged between the server and the devise calling in order to attach.
DIAL-IN: An Internet
account that can connect any stand-alone computer directly to the Internet. The
account is used by having a computer-based software application dial-in to an
Internet service provider (ISP). The software connects with the ISP and
establishes a TCP/IP link to the Internet that enables your software to access
Internet information. The computer that accesses a dial-in connection needs
either a modem to connect via a regular phone line or a terminal adapter (TA)
to connect via an ISDN phone line.
DIGITAL: Your CD player
is digital. It is a series of small samples of data playing together very
quickly (30,000 times a second). Digital recording of information means
representing the bits of data through ones and zeros. Playing the bits back to
again create what was recorded is called digital processing.
DIODE-TRANSISTOR
LOGIC (DTL): One of the first bipolar monolithic IC families of
logic gates. A diode in an IC logic gate performs the required logic with a
transistor amplifying and inverting the output. The DTL family has been made
obsolete by the Transistor-Transistor Logic (TTL) family.
DIRECTORY: A list of files
stored in the computer.
DISK: Two distinct
types. The names refer to the media inside the container:
A hard disc stores vast
amounts of data. It is usually inside the computer but can be a separate
peripheral on the outside. Hard discs are made up of several rigid coated metal
discs. Currently, hard discs can store 15 to 30 Gb (gigabytes)
A floppy disc, 3.5" square, usually inserted into the computer and
can store about 1.4 megabytes of data. This has become obsolete now.
DIRECT ADDRESS: A memory
accessing mode in which the contents of the accessed location is called the
OPERAND.
DIRECT MEMORY
ACCESS (DMA): A method of transferring blocks of data directly
between an external device and the computer system memory without the need for
intervention by the CPU. This method significantly speeds up the data transfer
rate, improving system efficiency.
DISK DRIVE: The
mechanical/electronic section that can accept and operate a compatible floppy
or hard disk. It may include several motors (for disk rotation and
reading/writing head positioning), position sensors, and control circuits.
DISK MIRRORING: simultaneously
storing a copy of information on another disc so that the information can be
recovered if the main disc crashes.
DISK STRIPING: storing a bit
of information across several discs (instead of storing it all on one disc and
hoping that the disc doesn’t crash).
DISK OPERATING
SYSTEM (DOS): A software program on a disk which coordinates the
operation, transfer of data, supervision, and control of a computer. This
software program must first be booted into the working memory of the computer
from the disk before it can operate.
DISK STORAGE: A method of
storing software programs and data on a rotating circular disk (either a floppy
or hard disk) coated with magnetic material, such as iron oxide. Data is
written (stored) and read (retrieved) by movable read/write heads positioned
over data tracks on the surface of the disk. Addressable portions of the disk
can be selected for read or write operations.
DISPLAY: A peripheral
device serving as a computer readout, such as a cathode-ray tube (CRT),
flat-panel (generally for laptop computers), or other readout devices. The
screen can be amber, green, or full-color display. Also called a MONITOR.
DNS: This stands for
Domain Name System. The Internet runs by assigning different sites “Names.”
They are actually 4-part strains of numbers associated with names, but names
nonetheless. Getting a DNS error means that the address you are attempting to
reach is not recognized by the Internet community.
DOCUMENTATION: Information
that explains how to use computer hardware or software. It is usually provided
as a manual or stored on a disk.
DOMAIN: A domain is a
computer, web site or network that is connected to the Internet. A typical
domain name looks like this: www.5starsupport.com. The
“www” prefix signifies that it is connected to the world wide web. The
“5starsupport” or body usually indicates the company name and the suffix “com”
is the indicates that it is a commercial site.
DONGLE: A device that
attaches to a computer to control access to a particular application. Dongles
provide the most effective means of copy protection. 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.
DOT-MATRIX
PRINTER: An impact printer with a computer-driven, multipin print element
(print-head). It create images by imprinting a series of tiny dots on a paper
to print a wide variety of character styles and/or finely detailed graphics.
Generally, these printers are extremely fast and are used for draft-quality
documents and precise graphics.
DOTS PER INCH
(DPI): The measurement of density on dot-matrix printers or other dot-matrix
devices. As the DPI increases, image clarity increases.
DOWNLOAD: The process of
transferring information from a web site (or other remote location on a
network) to the computer. It is possible to “download a file” or “view a
download.”
v. To transfer information from a web site (or other remote
location on a network) to the computer.
DOWNSTREAM: This refers
data that is received from an ISP. Upstream in the data you send back. Some new
technology allows for tremendous downstream data transfer rates (100 kilobytes
per second or more), but with very slow upstream rates (33.6 kilobits per
second or less).
DOWN TIME: A period of
time during which a computer is not functioning. It is inoperable because of
temporary or permanent failure of hardware or software, or when routine
hardware or software maintenance procedures are indicated.
DPI: Stands for Dots
Per Inch.
DRIVERS: A driver is a
software program that is the driving force behind a device. Each computer
device needs a driver. Many drivers are included with a computers operating
system when you purchase it.
DROP-DOWN MENU: A menu window
that opens vertically on-screen to display context-related options. Also called
pop-up menu or pull-down menu.
DSL: Digital
Subscriber Line. A method of connecting to the Internet via a phone line. A DSL
connection uses copper telephone lines but is able to relay data at much higher
speeds than modems and does not interfere with telephone use.
DTP: Desk Top
Publisher (ing): A PC Term that describes a
program that enables you to design, create and print a variety of projects such
as letterheads, birthday cards, calendars, business cards, invitations etc.
that would have previously only been possible by using the services of an
outside printers business.
DUAL CORE: This refers to
a new Central Processing Unit (CPU) structure. The difference between a single
core and dual core is that a dual core system has two CPU’s that are
electronically wired together. These two CPU’s wired together in parallel gives
twice the performance than that of its single core counterpart.
DUMB TERMINAL: This a video screen
that is seeing manipulation in another computer. Example: If you log in
to AOL, your computer is not doing the work — AOL’s computer is. You are just
being offered a window into that world. That window is your screen. It’s a
terminal, but it’s just watching — thus a dumb terminal.
DVD: Digital Video
Disc—Similar to a CD-ROM, it stores and plays both audio and video.
DYNAMIC RANDOM ACCESS MEMORY (DRAM): A type of semiconductor memory in which the presence or absence of a capacitive charge in each element of the memory represents the state of the bit (1 or 0). This charge must be periodically recharged (refreshed) to maintain the desired binary state of the element. See RANDOM ACCESS MEMORY.
DYNAMIC RANDOM ACCESS MEMORY (DRAM): A type of semiconductor memory in which the presence or absence of a capacitive charge in each element of the memory represents the state of the bit (1 or 0). This charge must be periodically recharged (refreshed) to maintain the desired binary state of the element. See RANDOM ACCESS MEMORY.
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