Daemon A daemon handles requests received by a computer system, sending them on to other programs. For instance, a print daemon would handle print requests while freeing up other applications in the process. This is why you can continue working whilst your computer sends a print job to the printer. Hypertext Transfer Protocol (HTTP) is a type of daemon on the Web that handles requests from users while they surf the Internet. In other words, daemons can be considered to be a program that allow programs to run more efficiently.
Data Characters grouped together in a specific pattern to which a meaning is assigned. Computers store data in codes like ASCII.  Data can include different sorts of information such as numerical data, colours, shapes and alphabetical characters.
Data Compression A technique for encoding data in such a way that it takes up less storage space on a disk or when transmitted.  Data that is encoded must be decoded (or expanded) in order to be restored to its original form.
Database A collection of related information stored together in some form of organised structure that when computerised it allows the data to be searched / sorted to allow the data to be presented in different ways. Examples of a database may be an address book, music collection, customer records, etc.
Database Engine The database engine is the software that stores and retrieves (and indexes) your data. You don't need to know about the engine because it works behind the scenes and you never directly interface with it.
Datagram Logical grouping of nformation sent over a network.
DCE Acronym for Data Communications Equipment.  Example of a DCE device is a modem.
Debug To locate and correct any errors in a computer program or to correct malfunctions in the computer or peripheral equipment.
Default This is a term meaning that if you choose nothing when presented with different options, the program (being Windows or any application) will automatically choose the option labeled as "Default" for you.
Defrag Short for defragmenting. When a file is saved to disk and then modified over time it will most probably end up being stored in several fragments on the disk. To defrag the disk is to run a utility (usually supplied as part of the operating system) to rearrange the contents of this disk so that all files are saved as a single fragment.
Degauss Degauss is just another word for "demagnetise." Magnetic fields build up in your monitor and distort the display (eg. the image or  colours look wrong). Monitors that use the old cathode ray tube are subject to this kind of magnetic build up. Many monitors automatically degauss themselves when they're turned on, so you don't have to worry about it. That initial "ping and click" is the monitor degaussing itself.
Denormalised data Term used when organising data in a relational database. With de-normalised data, repetitive data is stored for every record. For example, in a purchasing system the address of the customer would be stored for every record in the database for that customer.
Device driver Software used to control a specific device as it interacts with the operating system. You'll have one for your printer, CD burner, scanner, modem, etc. When you connect a new piece of hardware to your computer, either the OS will install one automatically or you will have to do it manually. In most cases, it is best to use the driver provided with the device and not the one written by Microsoft aa part of the OS.
DHCP Dynamic Host Configuration Protocol which provides a network's ability to dynamically allocate TCP/IP addresses dynamically so that they can be re-used. Typically, DHCP is used by ISP's and/or companies who have users that travel with their computer between different locations on their network.
Dialogue box A window that either requests or provides information. For example, when you do a File, Open... in a Windows application, the window that opens to allow you to select the file to open is a dialogue box.
Differential Backup A type of backup that will back up the selected files only if they are new or have been modified since the last full or incremental backup. This type of backup does not reset the archive bit.
Digital Certificate A method to verify that a user sending a message is who they claim to be and provides the receiver with a means to reply securely. An example of a company that provides these is Verisign ( ). Many banks use Verisign in an attempt to ensure that you are not dealing with a bogus site.
DirectX DirectX was designed by Microsoft to make multimedia run better on Windows. Instead of a thousand and one proprietary (and unique) programming interfaces, they created a standard for frustrated programmers.. If you're running a newer version of Windows, then DirectX may already be installed. If your system is without DirectX, you can always download it from Microsoft's site. DirectX games can even emulate features your system may not have; your racing sim will have semi-speedy 3D graphics... even though you may not have a 3D acceleration card.
Disaster Recovery Measures taken by a company to allow a company to continue using its computer equipment in response to natural or man-made disasters. Ideally, the measures taken would be preventative so that the effect of a disaster is either eliminated or minimised and involve the use of redundant hardware, software and other facilities.
Disc-at-once You can tell a CD Writer to use the Disc-At-Once method which records all of the information in one pass. This puts a table of contents or "lead-in section" at the beginning of the disc, then keeps recording until all information is down, and finishes with a lead-out section. After Disc-At-Once recording, nothing more can be recorded to the CD-R. This makes Disc-At-Once an inefficient way to store files though it is a good way to record music for play on audio CD drives or to make many copies of a single master CD-ROM.
Disk A magnetic surface onto which digital data can be saved and read back.
Disk Controller A hardware device that controls the writing and reading of data to and from a disk drive. In a PC, it is usually incorporated as part of a motherboard in a PC. In larger computer systems, it is a separate circuit board.
Disk Mirroring The process of writing the same data onto two separate disk drives. This allows a system to continue running if one of the disk drives in a mirrored pair fail. Mirroring can be controlled either by software or by a specially designed disk controller. Commonly used in servers and mainframes.
Disk Striping Spreading the data stored in a system across multiple disk drives which the system then sees as a single logical disk drive. Disk striping enhances performance because the system will write the each physical disk at the same time.  The more disks in the striped set, the better the performance gain. Commonly used in servers and mainframes.
Dithering Varying dot patterns to create the illusion of more colours than a palette actually contains, making images appear much more realistic.
DLL Acronym for Dynamic Link Library. These files are a library of executable functions or data that can be used by a Windows application. A program accesses the function by creating a link to the DLL file.
DMA DMA stands for "direct memory access," the process of moving data directly from memory to a device--such as a disk drive or monitor--by bypassing the CPU. To do this, a computer must be equipped with a DMA channel.
Dongle A dongle is a mechanism that allows only authorised users access to a specific application. One dongle might plug into a parallel port, while others are simply registration numbers. Dongles aren't used as much anymore but you may see them on occasion, particularly with high- dollar engineering software packages
Dot pitch The distance between adjacent dots of the same colour in a display. They are expressed in terms of millimetre (mm).
Download The act of transferring a file from the Internet (or a server) to your computer.
Drive Bay A drive bay is a space set aside within your computer in which you can install a hard drive, floppy drive, CD-ROM drive, or removable disk drive (such as a ZIP or JAZ drive). You can usually figure out how many drive bays you have by counting the blank panels on the front of your computer.
Drive Duplicator A drive duplicator is a stand-alone piece of electronic equipment that copies all the data from one hard drive to another very quickly. With this device, you can install new applications quickly across a large number of hard drives. It's also useful for upgrading hard drives in a large number of PCs.
DRM DRM stands for Digital Rights Management which is a way to protect digital media files, such as music and video, from copyright infringement.
DSR When a piece of hardware is ready for the next task or transmission, it can tell other hardware by sending a DSR or Data Set Ready signal. This term is generally used in relation with modems.
DTP DTP stands for "desktop publishing"--a class of personal computer software used to design and produce printed documents. Desktop publishing programs usually allow more sophisticated graphics placement, colour, and type handling than, say, a word processing program; many also make it easier to specify colours used by commercial printers. Popular desktop publishing programs include Adobe PageMaker, QuarkXPress, and, on the lower end, Microsoft Publisher.
Dual-ported RAM A type of RAM that allows two memory addresses to be read at the same time. The most popular type of dual-ported RAM is VRAM which is mostly used for video memory.
Duplex Printer A duplex printer is a printer which can print on both sides of a sheet of paper at the same time.
DVI Digital Video Interface. A new standard that improves image quality by delivering a digital signal from a graphics card to a monitor.
DVORAK Name given to a keyboard where the most common letters are placed in the middle of the keyboard.
Dye-sub Printer A dye-sub printer works by heating ribbons of coloured ink and then transferring the ink to paper--specially coated, expensive paper. The   result is true photo-quality output but at a price that might make most of us wonder why you wouldn't just take a picture in the first place. Dye-sub, by the way, is short for "dye sublimation." Another term for the same printing technology is "thermal dye transfer."
Dynamic HTML (DHTML) Advanced HTML extensions that use scripting, layers, cascading style sheets and the Document Object Model to create pages that react to user input without sending requests to the Web server.


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This page was last updated on Sunday, 14 December 2008