| Default | The configuration or settings that are set as standard by the manufacturer or supplier. Often the default settings are not really suitable, and are unlikely to be optimal, but they usually work. |
| Default Gateway | A setting (on Windows PCs it is in the Network Properties) which tells the computer the IP Address of the nearest Router that it should use to connect to computers outside the local Network. On most networks this information is supplied by a DHCP Server, but on a small network with no local server this must be set by hand. If your computer uses a Modem to dial-up to the Internet, the default gateway/router setting for the dial-up connection will be set automatically, along with the IP Address and DNS Servers. |
| Deprecated | Set to become obsolete, i.e. only included for backwards compatibility. Anyone writing HTML will soon come across this term, since many commonly-used HTML Tags are officially deprecated and should be avoided if you want your Web Pages to comply with best practice. See also Web Standards. |
| DHCP | Dynamic Host Configuration Protocol - Every computer on a Network must have a unique address. DHCP is a very widely-used system that allows the computers on a network to ask for a valid IP Address every time they are switched on, which helps to ensure that no two computers are using the same address. A DHCP Server hands out the addresses, usually along with a few other configuration details, and with a "do not use after" date. This is called "leasing". Before the lease expires, the lessee computer has to ask for a renewal of the lease. All this happens in the background and the user is not normally even aware of what address he/she is using. DHCP is normally used for dial-up connections to an ISP, even if the Client has a fixed address on its local network. Windows NT Server and its successors include the facility to act as a DHCP Server. DHCP is part of TCP/IP. |
| Directory | Directory has several meanings in computing: on the Web it probably refers to a "Yellow Pages" type of Web Site which has thousands of categorised Links to other sites. These tend to be heavy on the retail and financial services side, light on the not-for-profit and government services side. You don't need to be cynical about "information" to work that one out. |
| DivX | A proprietary file format for video, based on MPEG-4 (which is not proprietary). There is an Open Source version of DivX called OpenDivX, the creators of which forced the publishers of DivX to release the source code. |
| DMZ | Demilitarised Zone - A technical term relating to Firewalls. A DMZ is a section of a Network that is behind a firewall but separated from the rest of the internal network, possibly by another firewall. The computers in a DMZ, usually "Internet-facing" Servers such as Web and E-mail servers, can only connect to the external network (i.e. the Internet) so that if their security is breached by Hackers they cannot be used as a route into the internal network. |
| DNS | Domain Name System - One of the fundamental technologies of the Internet, which is why it is often mentioned in Browser error messages. Put simply, DNS is the real "directory enquiries" of the Internet, converting readable Web site addresses such as "www.google.com" into the real numerical addresses that networks actually use. See also Domain Name, IP Address and TCP/IP |
| DOM | Document Object Model - You need to know at least the basics of this if you want to write JavaScript, but otherwise probably you don't. The DOM describes the structural hierarchy (model) of Browsers and Web Pages in terms of a tree of object types. This allows Applications such as JavaScript to manipulate the browser and the displayed pages to achieve all kinds of effects. Cutting-edge browsers such as Mozilla Firefox let you see a Web page mapped onto the DOM, which can be a useful tool for learning HTML and JavaScript. |
| Domain Controller | A Server in a Windows Network that provides Login authentication, i.e. a "gate keeper". Confusingly, Windows domains have nothing to do with the Internet's DNS domains. Only the three Microsoft "Server" Operating Systems (Windows NT Server, Windows 2000 Server and Windows Server 2003) can be set up as Domain Controllers. |
| Domain Name | There are two distinct meanings that are similar but completely separate: a Windows-centric one and an Internet-centric one. The Windows meaning is normally only encountered when Logging in to a networked Windows computer. In any other situation "domain name" can be assumed to refer to a DNS domain; this is the Internet-centric usage. On the Internet, and most Networks that use IP, the Servers are given names to make it easier for humans (for why, see IP Addresses). The names are arranged in a sort of "family tree" hierarchy. Only the registered owner of a branch ("domain") may issue names for servers on that branch, or create additional branches ("child domains"). On the Internet there is a limited number of top-level domains (TLDs) and these have been agreed internationally. The TLDs include the international "com", "org" and "net" plus a raft of country-specific domains such as "uk", "de", "fr" etc. Each TLD has one or more "Registrar" organisations responsible for doling out ("registering") child domains for their area. In the UK the principal registrar is called "Nominet". TLD registrars choose a specific set of second level domains (such as "co.uk" and "org.uk"), which they then offer to register child domains for. It is up to individual registrars to set the rules for who can register these child domains and generally there are few restrictions, although there is wholesale/retail structure. Some domains however, such as UK academic domains "ac.uk" and "sch.uk", are very restricted. Domain names are big business and great for lawyers. For example, literally thousands of domains incorporating "eBay" have been registered in attempts to defraud unwitting punters. In the US there is now a "Truth in Domain Names Act" to prevent companies setting up misleading domains that might lure children to undesirable sites. In total there are millions of registered domain names. Sometimes individuals or organisations register a name even though they don't intend to use it themselves, simply to stop others using it. We have registered "rs-infotech.co.uk" for this reason. Domain Names aren't expensive. For example ".com" domains typically cost £12 per year retail. Beware "free" domain names, these are not Free Lunches. The catch is tucked away in the small print, typically a £100 fee to transfer the name elsewhere, the only way to get rid of the unpleasant banner adverts on your site. |
| Dot | Short for Dorothy. See also "Dot Com". |
| Dot Com | Usually means a business that depends entirely on the "Internet", as in the "Dot Com Crash" of 2000. Comes from the fact that one of the original and still the most desirable public "Domain Names" end in ".com". The original meaning of .com, "commercial", went by the board a long time ago. It is rare to be able to register a .com domain name that is a single English noun, common present participle or Real Name, because most have been registered already. Try it - you can look up whether a .com domain is registered at InterNIC's Web site at www.internic.net/whois.html. The UK registry, Nominet, is at www.nominet.org.uk. |
| Download | Transferring files such as documents or programs from a remote computer to your local computer. Fetching the latest update for your virus checker is an example of downloading. The opposite of Uploading. |
| Dreamweaver | Dreamweaver is Macromedia's market-leading, top-of-the-range Web Site creation tool, or "Web Editor". Dreamweaver has been the market leader and professional tool of choice for many years, to the extent that the facilities available in it, or lack of them, has had a significant impact on the rate of uptake of Web Standards. Nowadays there isn't much, in terms of creating a Web site, that can't be done using Dreamweaver, however it is expensive to buy and has a steep learning curve, so we wouldn't recommend it to beginners. |
| DRM | Digital Rights Management - A very controversial topic. DRM is an umbrella term covering several different technologies that copyright owners apply to their wares, when supplied in digital form. DRM is sometimes called "copy protection", but technologically it goes much further than that. DRM technologies range from the straightforward scrambling techniques used to prevent unauthorised copying of DVDs for example, to much more sophisticated and some would say, sinister, implementations that aim to control exactly when, where and how a product is consumed. Often, consumers of the latter are forced to accept the arrogant assumption of the supplier that they will remain in business for the lifetime of the product, and have to take it on trust that the supplier will not make malicious use of their total control. Sony BMG is one multi-national that has already overstepped the mark, landed itself in court and quite rightly earned itself a great deal of bad publicity through trying to push the boundaries of DRM with its discredited "XCP" Spyware system. Unfortunately this is only the tip of a growing iceberg, and consumer ignorance and laziness is playing into the hands of ruthless corporations. As ever, caveat emptor - and make sure you know what you are buying, or not. |
| DSL | Digital Subscriber Line - A type of telephone connection that allows both talking and computer connections simultaneously, using existing old-fashioned telephone wiring. There are two types, ADSL, which is the standard domestic type of DSL normally found in the UK, and SDSL which is often used by schools and businesses. See also Broadband, Contention. |