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BASICS TUTORIAL ON PCS AND USE OF THE INTERNET
GLOSSARY OF TERMS USED IN THE PC AND INTERNET WORLD
GLOSSARY (d-e)
Data: Historically, 'data' is the plural of 'datum' (but it is now also universally accepted as the singular!). In computing, it is the content of a computer file that is not an executable (qv). It is file-hosted meaningful information (in the form of text or values) that may be held in standard, eg Windows, folders but may alternatively be stored in an organised database (qv) such as MS Access.
Database: On a PC (for offline records) or a website server (for online records), a database such as MS Access or MySQL is capable of holding records of a wide variety of data, individual elements of which can be quickly added or retrieved.
Data Encryption Key (DEK): Used for the encryption of message text and for the computation of message integrity checks (signatures). See also: Encryption.
Default: The value or option that will prevail if not positively changed.
DEK: See: Data Encryption Key.
DeskTop Publishing (DTP):
DHTML: See: Dynamic HyperText Mark-up Language.
Dial-up: A temporary, as opposed to dedicated, connection between machines established over a standard 'phone line.
Digital Subscriber Line (DSL): A service being offered by the world's telephone companies that combines a permanently-on broadband digital Internet connection at speeds up to 8Mb/s (June, 2003) with a telephone connection on TOPS (The Old Phone Line), ie an old twisted-pair telephone line. See also Asynchronous Digital Subscriber Line and Synchronous Digital Subscriber Line.
Distributed database: A collection of several different data repositories that looks like a single database to the user. A prime example in the Internet is the Domain Name System (DNS) (qv).
DNS: See: Domain Name System.
Domain: 'Domain' (or domain name) is a heavily overused term in the Internet. It can be used in the Administrative Domain (qv) context, or the Domain Name System (qv) context. In the latter context, an owner's domain name is that part of all available URLs (qv) after 'http://www' (or just 'http://' for big operators apparently) and that part after '@' in any e-mail addresses (qv).
Domain Name System (DNS): The DNS is a general purpose distributed, replicated, data query service. The principal use is the lookup of host IP addresses based on host names. The style of host names now used in the Internet is called 'domain name', because they are the style of names used to look up anything in the DNS. Some important domains are .COM (commercial) .EDU (educational) .NET (network operations) .GOV (government) and .MIL (military). Most countries also have a domain, eg .US (United States) .UK (United Kingdom) and .AU (Australia). See also: Fully Qualified Domain Name.
Doorway page: A webpage that serves only as an entry point through which users click to go to the actual home page. In the past, search engines would classify and retrieve websites based primarily on meta tags, but now each search engine has its own set of criteria that you must adhere to if you want your site listed near the top of the results, ie a separate doorway domain should be created for each search engine so that it complies with each engine's criteria. See also: Buffer page.
Dot address (dotted decimal notation): Dot address refers to the common notation for IP addresses of the form A.B.C.D; where each letter represents an octet, which is a value represented by eight binary digits (a byte!) in decimal notation (0-255). See also: IP address, Byte.
Downloading: The process of transferring a file or files from a source on the Internet (or another PC actually) to your PC.
DSL: See Digital Subscriber Line.
DTP: See: DeskTop Publishing.
Dynamic: In the context of a web page, dynamic normally means that server-side includes (SSI) (qv) allow the user to interact with the page, eg via online forms, although it can relate to client-side facilities in an HTML page such as Cascading Style Sheets (CSS) (qv) and JavaScript/VBscript scripts (qv), such an environment being known as Dynamic HTML (DHTML)(qv).
Dynamic Hypertext Mark-up Language (DHTML): An environment, ie not a language at all, allowing facilities such as CSS (qv) and JavaScript/VBscript (qv) in an HTML page to make a web page client-side dynamic.
Electronic mail (e-mail): A system whereby a computer user can exchange messages with other computer users (or groups of users) via a communications network. Electronic mail is one of the most popular uses of the Internet.
e-mail address: The domain-based address that is used to send electronic mail to a specified destination. For example the author has two e-mail addresses: 'dave@eclipsetbs.co.uk' and dave_stuttard@lycos.com.
Encoding: The process of rewriting and/or transferring media sources from one format to another. For example, you can encode a VHS tape into a RealVideo file.
Encryption: Encryption is the manipulation of a packet's data in order to prevent any but the intended recipient from reading that data. There are many types of data encryption, and they are the basis of network security. See also: Data Encryption Standard.
Ethernet: A widespread networking scheme most commonly known as 'the hardware device that enables the LAN to work at the office'. Ethernet was originally developed by Xerox PARC and further developed by DEC and Intel. There are now several speeds, including 10BASE-T, with transmission speeds up to 10 Mbps, Fast Ethernet (or 100BASE-T), with transmission speeds up to 100 Mbps, and Gigabit Ethernet, which offers the highest level of backbone support, at 1000 Mbps. See also: Local Area Network, Token ring.
Ethernet meltdown: An event that causes saturation or near saturation on an Ethernet network. It usually results from illegal or misrouted packets and typically lasts only a short time.
Executable: A file that is a computer program (and therefore potentially includes a computer virus), ie a series of computer operations are carried out when Run is selected (as opposed to a media or database file, which contains data only).
Extension: The set of characters after the dot in a file's name is the file's extension. It determines how the file is formatted and viewed. For example, a file named 'index.html' is coded in HTML and therefore must be viewed with a compatible program (such as a Web browser or HTML editor).
Details updated: June 15 2010
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