Computer Science

Data
Information, as recognized by a computer and transmitted across a variety media, from computer or network to another, using a specific protocol, or language.

Data Bus
A group of parallel conductors (circuit traces) found on the motherboard, which is used by the CPU to send and receive data from all the devices in the computer.

Data Encryption
Data that is encoded for security reasons, at the sender's level and then decoded at the recipient's level.

Data Link Layer
The Data Link layer is the second lowest layer in the OSI model. It is the last stop before the data packets are placed on the media for transmission. The Data Link layer splits data into frames, which are large areas of data that are split into smaller non-contiguous blocks, for sending on the Physical layer. It also receives acknowledgement frames. It performs error checking and re-transmits frames that were not received correctly.

Data Mining
Analyzing data to find relationships not previously discovered.

DC
Direct Current

Default Gateway
When you type the IP address of the gateway routers you have installed on your network, whichever one appears first on the list is considered the default gateway.

Defragmentation
The process of running a program to organize the files on a hard disk so that they are once again contiguous on the disk. Will help speed up the hard disk.

Demand Priority
This access method is designed for the 100 Mbps Ethernet standard 100VG-AnyLAN

Device Driver
A program that extends the operating system to support specific devices.

DHCP
Dynamic Host Configuration Protocol - A method for leasing and maintaining that lease for IP addresses and related information to clients.

Digital Signal
Baseband uses digital signals over a single frequency. (Simple "on" or "off" signal.)

DIMM
Dual-Inline-Memory-Module

DIPP
Dual-Inline-Pin-Package

Directory
Locations for storing files, not unlike a filing cabinet in the office.

Disk Mirroring
The use of two or more hard disks that "mirror" the main one, so that one can take over for the other if it fails.

Disk Striping
Also called data striping, this is the dividing into segments of logically sequential data, such as an individual file, so that the segments can be written to multiple disk drives, in a round-robin fashion. If the processor is capable of reading or writing data faster than a single disk can supply or accept it, the second disk can locate the next segment while data is being transferred from the first disk.

DLL
Dynamic Link Library

DMA
Direct Memory Access - Allows a peripheral device to access the memory of a computer directly without going through the CPU making transferring data to or from external devices faster.

DMA (Direct Memory Access)
A limited form of bus mastering, DMA allows a device to read and write memory without intervention by the CPU.

DNS
Domain Name System

Domain Name
The unique name that identifies an Internet site. Domain Names always have two or more parts, (1st level and 2nd level) separated by dots. The part on the left is the most specific, and the part on the right is the most general. A given machine may have more than one Domain Name but a given Domain Name points to only one machine.

DOS
Disk Operating System - The system used by most PCs as the operating system software to manage hardware, data and applications.

Download
The ability to transfer a file to a remote computer. Downloading means to receive a file from another computer.

DRAM
Dynamic Random Access Memory - Memory that requires a refresh signal to be sent to it periodically.

DSL
Digital Subscriber Line - A method for moving data over regular phone lines. A DSL circuit is much faster than a regular phone connection, and the wires coming into the subscriber's premises are the same (copper) wires used for regular phone service.

DSMN
DSMN (Directory Service Manager for NetWare) is another add-on utility that is used to integrate user and group account information between the two operating systems.

DUN
Dial-up Networking

DVM
Digital Volt Meter

Dynamic Pricing
Refers to the surge and descent of demand that affects the prices of online products and describes that prices are constantly changing to reflect supply and demand.