IT Glossary: computer jargon explained D - F

DAT
Digital Audio Tape. DATs are mainly used for storing back-up data. They provide a convenient medium for storing large amounts of data where immediate access to the data is not so important. DATs are gradually being replaced by DLTs which offer higher capacity and speed.

Dial-up
The original method of connecting to the Internet, in which a “telephone call” was dialled up to make the connection between PC and internet service provider. The connection remained only until the call was terminated and was charged on a “time-connected” basis. This is being rapidly replaced by broadband.

DLT
Digital Linear Tape. DLTs are used to store back-up data and are much faster than DATs, their main rival.

Domain
A website address owned by a person or company, for example  www.business-cohesion.co.uk

DOS
Disc Operating System. This was Microsoft’s original operating system for PCs before Windows.  It was a text based system therefore relatively unfriendly by the standards of today. The “DOS Prompt” or “Command prompt” is still used in Windows today for troubleshooting and specialised tasks. This prompt mode uses many of the same commands that originated from DOS.

Download
If you are downloading information, you are transferring it down from the internet, or from a network, and onto a computer. A “download” is a file that has been downloaded.

Driver
A driver is a piece of software that controls hardware. Also known as a “device driver” as it controls an attached device such as a printer or scanner. Drivers often need updated to maintain the best performance and to work with newer operating systems.

DSL Filter
A “splitter” device that fits into a telephone socket and allows one telephone line to be shared between a computer broadband connection and a voice telephone. You need DSL filters at every telephone if a broadband connection is in use, otherwise the quality of both the telephone line and broadband will be affected.

DVD
Digital Versatile Disc. This is a disc that looks very much like a CD except that it is capable of storing a lot more information. Because of the increased capacity, DVDs are often used to store films, but they can also be used to store other types of data. DVD recorders are becoming standard in computers, and software is being increasingly provided on DVD rather than CD.

DVDR
Digital Verstaile Disc Recordable. This is a DVD onto which you can record, or write, data once only.

DVDRW
Digital Versatile Disc ReWritable. This is a DVD onto which you can record, or write, data again and again, unlike a DVDR.

e-commerce
Electronic commerce. This describes online shopping, in which a sales transaction is made via a website and internet connection.

Encrypt
To write data in an encoded form so that it cannot be read by anyone who is not meant to read it. This is useful when sending data over the internet as it prevents the data from being read by hackers or anyone else.  For example, credit card numbers and personal details are often encrypted when you buy things online.

Extranet
This is an extension of a company’s Intranet making parts of it available to specific people via the Internet.

FAST
Federation Against Software Theft. An organisation which aims to stop software piracy by ensuring businesses are correctly licensed to use software.

File Server
A computer at the centre of most networks which stores and makes available files and other services to client computers on the network. Also known as a server.

Firefox
An alternative browser. Established in 2003 with support from America Online’s Netscape division. Firefox can be installed on a Windows computer and used as an alternative to Microsoft Internet Explorer.

Firewall
A program (or device) that acts as a protective wall between your computer and the internet. It helps to prevent access to your computer by hackers and other unauthorised users. If you use an always-on broadband connection then you need a firewall – either as part of the broadband hardware or as an additional software add-in.

Firewire
A fast hardware technology for connecting devices to your computer. Not fitted to all computers, this requires a Firewire port  (connector) on your computer. Video cameras and other devices which use high volumes of data will often be Firewire devices. Also known as IEEE 1394 and I-link.

FTP
File Transfer Protocol. A way of transferring files to or from an Internet Server. This is often how you upload web pages to the Internet.