Appendix Glossary D

In the left margin you will find links to the glossary categorised alphabetically. Some of the pages are quite long and may take a few moments to load if you use a modem. This glossary is always being updated.

Glossary - D

DAC - A device that converts digital data into analog signals.

Daemon - In UNIX, a program running all the time in the "background" (that is, unseen by users), providing special services when required. An example of a daemon is biff, which lets you know when mail arrives.

Daisy Chain - The sequential connection of hardware devices with cables.

Data - In the world of computing, pieces of information are stored and communicated in digital form. Anything that is to be processed or stored by a computer is considered data. It is apparently a little known fact that the word "data" is the plural form of the word "datum" and is to be treated grammatically as such. I'm not trying to popularise the use of the word "datum" here, I'm merely trying to offer the fact that the word "data" really should not be referred to as a singular noun. If you're not interested in crap like this, you've probably stopped reading by now, so I will ramble on by offering an example. The sentence "My data has become corrupt!" should really be "My data have become corrupt!" Of course, if you have problems like corrupted data on your hands, then you probably have bigger issues on your mind than grammatical consistency. Data is a precise piece of information. This is what is created and changed by using the computer. It can be anything at all. A word processing document, a spreadsheet, a database.

Data Mining - Data mining uses complex algorithms to search large amounts of data and find patterns, correlation's, and trends in that data. A data-mining application can create a model that can identify buying habits, shopping trends, credit card purchases as well as perform many non-commercial functions.

Data Separator - On a hard disk drive that stores data and timing information in an encoded form, the circuit that extracts the data from the combined data and clock signal.

Data Transmission Speed - The number of bits that are transmitted per second over a network cable.

Database - A means of organising and storing elements of information electronically so that they are readily available for retrieval and analysis. For example, I keep a database of all my "Gladys Knight and the Pips" albums.

Database Default - This means the standard choice, option, or selection automatically taken when you don't choose something else.

Daughter Card - This is a part which can plug into the computer via expansion slots, aka expansion cards.

DCC - Direct Cable Connection. A simple networking set-up under Windows 95/98, often using a cable between two computers' parallel ports.

DDR SDRAM - (Double Data Rate Synchronous Dynamic Random-Access Memory) The latest generation of SDRAM technology. Data is read on both the rising and the falling edge of the computer clock, thereby delivering twice the bandwidth of standard SDRAM. With DDR SDRAM, memory speed doubles without increasing the clock frequency.

Dead Link - A Web page that no longer exists, prompting an error message. A dead link may be the result of a Website that has ended operations or moved.

De Bigulator - A highly experimental device that is purported to possess the capability of taking a full-sized person and reducing him or her to microscopic size. So far, the de-bigulator has only been successfully tested on cartoon characters. Restoring the subject to normal size would require the use of some sort of "re-bigulator", the very notion of which is preposterous. To those who don't believe that such a term exists, I would like to personally vouch for the cromulence of this word.

Debug - The act of eradicating all programming errors within a piece of software before it is ready for use. The term has its origin in the early days of computing, when computers were the size of moving vans and lapses in functionality could often be traced to actual insects getting stuck inside of their internal workings. I'm not kidding.

Decompression - Data decompression is used to restore compressed data to its original form.

Dedicated Line - A telephone line that is leased from the telephone company and used for one purpose only. In the early days of the Internet, it was a line dedicated to a server.

Dedicated Server - A computer on a network that is assigned to function only as a resource server and cannot be used as a client.

Dedicated Servo - A positioning mechanism using a dedicated surface of the disk that contains timing and positioning information only, as compared to surfaces that also are used for data.

Default - A setting automatically assumed by computer hardware or a software application with regard to various operating functions. For example, when starting, a word processing program defaults to certain margins, spacing, and fonts set by the program's developer. Many default settings in both hardware and software can be changed to suit the user's specifications.

Defect Management - A technique ensuring long-term data integrity. Defect management consists of scanning disk drives both at the factory and during regular use, deallocating defective sectors before purchase and compensating for new defective sectors afterward.

Degauss - To demagnetise.

Desktop - In a graphic user interface such as the Mac OS or Windows, the desktop is the name given to the area of the screen that appears immediately before the user. The desktop is usually occupied by links to commonly used files, functions, and directories. The desktop often becomes the repository for files and directories that the user cannot think of another place to store, in which case it begins to resemble the top of my actual desk, but without the pencil sharpener and empty ginger bottles. On a purely technical note, it is worth mentioning that the contents of the desktop are actually stored within the hard drive in a particular spot that is designated by the system as the desktop directory.

Desktop Publishing - The use of a personal computer to design and produce professional quality printed documents. There are hundreds of software programs available allowing users to typeset and place illustrations and photographs in a wide variety of printed materials from brochures and manuals, to books and posters. Among those highly rated by both home users and individuals in the publishing industry, are Adobe PhotoShop and Adobe PageMaker.

Device - Networking equipment such as a hub, switch, bridge, router, etc.

DHCP - DHCP or dynamic host configuration protocol. DHCP allows client computers to be configured automatically; when a computer is switched on, it searches for a DHCP server and obtains TCP/IP set-up information.

Dialog Box - A window appearing on the screen offering the user information or options as to the next step in the present application. For example, when setting up the layout for a document in a word processing program, a dialog box is available offering the user options on the size and style of the font, margins, and possibly the colour of the text.

Dial In - A network connection that is accessed by dialling in to a computer through a telephone line. Once connected, your computer acts as if it were a network host. This type of service is often called SLIP, CSLIP or PPP.

Dial-up Connection - One computer connected to another utilising a telephone connection and a modem.

Digital - Information encoded and expressed with the use of binary numbers representing many values in the real world. Digital information is distinguished by the fact that only predetermined values may be represented using zeros and ones. For example, a digital thermometer would display the temperature using pre-assigned values. On a digital thermometer, the temperature might read 76.2. The next higher reading available might be 76.3. The true temperature, however, could range anywhere between 76.2 and 76.3, such as 76.21, .22, .23 etc. The possible values existing between 76.2 and 76.3 are infinite, but the thermometer, limited by design, can only display pre-set values. Consequently, pinpointing exact values represented by digital data is virtually impossible. Though limited in this way, digital information has many advantages because extremely close approximations are easily achievable. Digital data is also easy to store and manipulate.

Digital Audio - Sound recorded and transmitted in a binary format.

Digital Camera - A camera that encodes images without the use of film and records them directly to a disk or a computer.

Digital Computer - A machine that expresses data using a system of pre-set values. Digital computer representations can be broken down to simple binary expressions. All modern computers are digital as opposed to analog computers which would express values as individual points on a continuum. A slide-rule would be an analog computer.

DIMM - (Dual In-line Memory Module) - A printed circuit board with gold contacts and memory devices. A DIMM is similar to a SIMM, but with this primary difference: unlike the metal leads on either side of a SIMM, which are "tied together" electrically, the leads on either side of a DIMM are electrically independent. A type of memory common in Super7 and Pentium II motherboards. DIMMs can be added one at a time. Consult your system's manual to ensure the right type of memory - there are many varieties.

DIP - (Dual In line Package) A DRAM component packaging. DIPs can be installed in sockets or permanently soldered into holes on the printed circuit board. The DIP package was extremely popular when memory was installed directly on the motherboard.

Dir - (directory) In the operating systems DOS and OS/2, the command that calls up all the files in a particular directory.

Direct connection - A connection, such as SLIP or PPP, which makes your computer a live part of the Internet. Also known as full IP access.

Direct Rambus - Rambus technology's third generation, which offers a completely new DRAM architecture for high-performance PCs. Data transfers at speeds up to 800MHz over a narrow 16-bit channel, compared to current SDRAM, which operates at 100MHz on a wide 64-bit bus.

Directory - This is the place where a collection of files is kept! Every disk has one main directory. This is called the root directory. Usually attached to this directory are related or subdirectories. When you save a file to the disk ... it is saved to a particular directory. You can view the files in a given directory be using the DIR command...which means DIRECTORY.

Discussion Group - A group of people exchanging ideas and thoughts online encompassing a wide variety of topics of interest either in a chat room, interactive live chat, message board, or some other public discussion forum.

Disk - In general, any circular-shaped data-storage medium that stores data on the flat surface of the platter. The most common type of disk is the magnetic disk, which stores data as magnetic patterns in a metal coating. Magnetic disks come in two forms: floppy and hard. Optical recording is a newer disk technology that gives higher capacity storage but at slower access times. DMA - Acronym for direct memory access. A process by which data moves directly between a disk drive (or other device) and system memory without passing through the CPU, thus allowing the system to continue processing other tasks while the new data is being retrieved.
This is the place on the computer where information is stored. There are two kinds of disks: hard and floppy. Hard disks are permanent and attached to the insides of the computer. Floppy disks are portable and come in two width sizes: 3.5" and 5.25".

Diskette - This term describes the small floppy disk format that is commonly used to store and transport small amounts of data. While the word has been used to refer to a number of different shapes and sizes of disk, most diskettes in common use today are 3.5 inches in diameter and have a capacity of 1.4 megabytes, which is just enough space to hold those files that you will never actually look at again, but feel the need to carry home in your briefcase.

Display - This is another term for the computer screen or monitor. However, it means more precisely: what is actually displayed on the screen rather than the monitor itself which is the hardware which produces the display.

Distributed Printing - An information delivery model in which the file to be printed is completely prepared for output at one location and is then sent electronically to one or more separate locations for final printing. This allows for nearly immediate distribution of printed documents over a far-reaching geographical area. Thanks to distributed printing, a national or even international audience can appreciate that nifty fresh ink smell.

DNS - "Domain Name Server" A DNS is a computer whose job it is to tell other computers where to look on the Internet for a particular website or group of websites, which are assembled into designations called "domains." Computers communicate with each other by exchanging sets of numbers and not by forming sentences out of words as humans do. For this reason, Internet addresses are actually defined by strings of numbers called IP addresses. In order to express these names and locations in a language that humans can remember and communicate effectively, a translation must take place. This translation is performed by Domain Name Servers, which then make the results available to other computers on the Internet, as well as those within the LANs to which they are connected.

Document - This is a file created by a word processor which contains formatting information, text styles, fonts and the like. This is opposed to a regular text file which just contains textual content and can be viewed by typing the TYPE command.

Dock - To attach or connect, usually one hardware device to another.

Docking Station - A fixed location that makes accessories available to a laptop computer. These might include a permanent power supply, a printer, or a scanner.

Domain - A domain is a division of the Internet. Each domain is owned by a particular organisation, although some organisations own many different domains. Technically, each domain is defined by a specific IP address, which is very often translated from a numerical designation to a verbal one (e.g., "206.65.104.xxx" is also known as "www.asap.net"). For practical purposes, companies use unique domain names to make their websites easier to remember. The last three letters in a domain name are used to designate what type of organisation will be using a given domain (e.g. ".com" refers to a commercial interest ".gov" is the domain type for government organisations). A domain name remains the property of the owning entity until they stop paying the annual fee for its use or sell it to another organisation for a ridiculously inflated price...aah, capitalism.

Domain Name - A domain name is another way of referring to the Internet address of a computer or group of computers on the Internet. Whereas an Internet address is made up of numbers (e.g. 144.2.45.6) and therefore difficult to remember, a domain name (e.g. btinternet.com) is made up of meaningful words.

DOS - "Disk Operating System" While the term DOS at one time referred to any disk-based operating system running on a computer, use of this term today is usually directed to the Microsoft DOS (MS-DOS) that was created to run on the Intel-based PCs. While Windows and the Macintosh OS are graphical user environments, DOS is text based. This means that users of DOS need to learn the specialised codes necessary to perform tasks. The concept is a little bit like calling a square-dance for your computer. Just don't expect it to "do-si-do" when you type "DEL *.*"

DOS Memory - This is another term for conventional memory, which is the basic 640K of memory in a computer.

Dot Matrix - This is a type of printer which uses a series of pins to create an image on paper. Dot matrix printers are the most economical way to print information.

Double Click - To press a mouse button (usually the left) two times in quick succession to start a program or initiate a command.

Download - The act of copying a file from a network or large data repository (such a web page or FTP site) to an individual computer's disk drive. Simply stated, downloading is the process of "getting" a file.

DPI - "Dots Per Inch" DPI refers to the resolution of a given image file, expressed by the number of individual pixels that can be stored within each inch of the picture. Higher numbers associated with DPI do represent a greater potential for image quality, but certainly do not guarantee it. There are plenty of 1200 DPI files out there that still look really lousy. It's also worth keeping in mind that higher resolutions result in larger file sizes.

DRAM - (Dynamic Random Access Memory) The most common form of RAM. DRAM can hold data for only a short time. To retain data, DRAM must be refreshed periodically. If the cell is not refreshed, the data disappear.

DreamWeaver - Dreamweaver is the name of the application that is available from Macromedia to provide users with a graphical interface for the creation of web pages. This type of program is commonly referred to as an "HTML editor" because its job is to generate HTML files based on the commands executed in the page layout interface available to the user. Other HTML editing packages include Microsoft FrontPage and Adobe PageMill. The alternative to using a program like this to create web pages is to either use a text editor and enter the HTML codes directly, or get someone else to make your web pages for you (a very popular choice). As I'm sure you already know, Dreamweaver is also the name of the soulful rock anthem performed by the legendary Gary Wright.

Drive geometry - The functional dimensions of a drive in terms of the number of heads, cylinders, and sectors per track.

Driver - A software program that allows a computer to use and communicate with equipment or peripherals installed on the computer. For example, network interface cards (NICs) require drivers to allow the computer to communicate with the network through the NIC.

Dual Banked - A memory module having two banks.

Dual Independent Bus - (DIB) An Intel developed bus architecture that offers greater bandwidth by having two separate buses (frontside and backside) access the processor. Pentium II computers have DIBs.

Dump - This is a computer term which means to wash out one thing and dump it into another. Eg. a screen dump takes the information displayed on the screen and literally dumps it out to the printer.

DUN - Dial Up Networking. A way to connect to a network, including home networks, by dialling in over phone lines to a modem on a computer acting as a server.

Duron - AMD's least expensive member of the Athlon family, Duron is comparable to (but faster than!) Intel's Celeron.

DVD - "Digital Video Disc" The DVD standard was created as the next generation of high-capacity optical discs. Its ultimate goal is to supplant CD-ROM as the medium of choice for the distribution of electronic content. A single DVD can hold several gigabytes of information, which was designed to give it enough storage capacity to deliver digitised full-length motion pictures to a specialised playback device (hence the name Digital "Video" Disc). If a DVD has can hold that much digitised video, just imagine how many plain text files you can get on one of those babies.

Dynamic HTML - Also called dynamic content, information on a Website or Web page that is constantly being updated, usually daily, but sometimes as often as a user refreshes the page. Some dynamic content is instantaneously created according to a keyword used in a search.