ATM

Asynchronous Transfer Mode: a probable successor to TCP/IP

avatar

One's representation in a virtual reality. If one is Krishna, one's avatar is likely to be blue and beautiful-- but one may have many avatars for different purposes.

bandwidth

The amount of data which can be delivered through a given channel. Measured in bits per second.

baud

Common but erroneous synonym for "bits per second". Actually means "marks per second": for example pressing a telephone keypad produces one "mark", but this can have any of 16 values (each of which is a two-tone chord), and so represents 4 bits. So in this case one button-per-second = one baud = four bits-per-second. Not a lot of people know that.

bit

BInary digiT: the smallest unit of information, representing a yes/no or one/zero value. See byte.

BITNET

The Because It's Time NETwork; a proprietary network protocol for connecting IBM mainframe computers.

browser

A program which allows you interactively to explore a web of interconnected documents; relates as a client to the Web's server computers.

byte

Eight bits: the standard "chunk" of digital information. That full stop is represented in most computers by the eight-bit byte 00101110. In other contexts this byte might represent the decimal number 46, or a sort of lime-green colour in a low-resolution graphic.

client

In this context, a computer program which asks a server for... stuff.

co-ax

Co-axial cable has one conductor (metal wire) forming a cylinder surrounding the other. This allows it to carry much higher-frequency signals than "twisted-pair" cable -- and hence more data.

DNS

The Domain Name System: the process by which the names of computers are translated into the IP numbers actually used to route packets of data. Each ISP maintains a table translating common domain names; if it doesn't know, it knows a computer which knows a computer which does know.

document

Used on the Web to mean any data which makes sense to a suitable human: not just text, but sounds and movies.

domain name

The nearly-human-readable "address" of a computer on the internet. This paper exists on the computer whose domain name is www.poptel.org.uk; reading from the right-hand end, this is:

.uk

in the "uk" (United Kingdom) top-level domain;

.org

in the "org" (non-profit) sub-domain;

.poptel

in the "poptel" (organisation name) sub-domain of that;

www

the local (within poptel) name of the computer

(See URL).

DVD

Digital Video-Disk: the same shape and fundamental technology as a CD-ROM, but capable of storing up to two hours of MPEG-2 moving pictures.

email

Electronic mail: the exchange of written messages by sending computer documents over telephone lines and other networks.

fibre

Fibre-optic cables convey data coded in pulses of (laser) light, which are trapped inside a thread of very special glass which is notoriously thinner than a human hair.

FIDO

A "store-and-forward" network based on cheap personal computers. These store messages, usually until night-time, and then dial a neighbouring computer to exchange "what's new". Selected computers dial "hosts" which have full internet connections to exchange messages with the rest of the net.

ftp

File Transfer protocol: a means of allowing one computer connected to the internet to explore (a selection of) the files of another, to retrieve them and to send files to that remote computer.

giga-

Prefix meaning "thousand million" (see kilo-).

gopher

A protocol for building a global catalogue of information held on computers which are connected the internet. "Gopherspace" is a deeply-nested tree of Tables of Contents for electronic documents.

Hertz

Cycles/events per second.

HTML

HyperText Mark-up Language: the coding system which defines the appearance and functionality of Web documents, thus:

<DT><STRONG><A NAME="HTML">HTML</A>
</STRONG> 

<DD><A HREF="#HyperText">HyperText</A> 
Mark-up Language: the coding 
system which defines the appearance 
and functionality of Web <A HREF="#web">
Web</A> <A HREF="#document">
document</A>s, 

HTTP

HyperText Transfer Protocol: the protocol under which your Web browser requests documents from a server. The documents or file contents may be HTML, or something else. "http" is used as a protocol prefix in URLs.

HyperText

Documents with the addition of "hot links" -- words or pictures which you can "click on" (or otherwise activate, if you hate mice) to go to another document or to another place in the same document.

IP

SeeTCP/IP.

IP number

The "actual" address of a computer on the internet. The domain name www.poptel.org.uk is mapped by a magical process to the IP number (at the time of writing) 193.82.214.232. More than one domain name may map to the same IP number.

ISDN

Integrated Services Digital Network: two 64 bit-per-second "channels" over existing twisted-pair telephone cables.

ISP

Internet Service Provider; the owner of a computer which is directly connected to the internet and to modems which home users can dial into.

ITU

International Telecommunications Union

kilo-

Prefix meaning "thousand". One kilo-gram is 1000 grams; one mega-gram is 1,000,000 grams or one metric tonne.However, in digital usage "kilo" usually means 1024, "mega" 1024 times 1024 = 1,048,576, and so on: for computers, these are "round numbers".

mainframe

Roughly speaking, a large computer designed to support many users simultaneously.

mega-

Prefix meaning "million" (see kilo-)

MPEG

Named for the Motion Picture Experts Group, this is a series of standards for compressing moving pictures.

peta-

Prefix meaning "thousand million million" (see kilo-).

pixel

Picture element: one "dot" on a display screen.

protocol

Among diplomats, the rules for a conversation: who speaks first, how we decide what language to speak, how we check that the message received is close enough to that sent. In computing, the same.

protocol prefix

The initial component of a URL, which indicates the protocol under which information is being requested. Common values include "http://", "gopher://", "ftp://", and "mailto:".

resolution

For visual images, the level of detail present: measured in pixels per unit length.

server

In this context, any system which delivers data in response to requests formatted according to a protocol.

TCP/IP

Transport Control Protocol/Internet Protocol; the internet standards or protocols for getting raw information from one digital device to another. Higher-level protocols (that is, those closer to human needs) like http and gopher "sit on top of" TCP/IP in roughly the sense that the grammar of this sentence "sits on top of" the use of the Roman alphabet for raw words.

tera-

Prefix meaning "million million" (see kilo-).

twisted-pair

Conventional telephone wiring with two plain wire conductors (c.f. co-ax).

Unix

An operating system for computers, developed at Bell Labs and used by most large university systems. Unix "imagines" the universe as consisting of streams of text which are fed or "piped" through processes; it is well-adapted for running many small processes in parallel.

URL

Universal Resource Locator: a unique global identifier for a file, which may contain a document or a computer program or just about anything digital. A URL consists of a protocol prefix; the domain name for the computer on which the file is held; a path through that computer's directories or "folders" to the file, and the file name. This file exists at the URL http://www.poptel.org.uk/nuj/mike/glossary.htm, which breaks down:

http://

protocol prefix

www.poptel.org.uk

domain name

/nuj/mike/

path

glossary.htm

file name

UUCP

Originally, the Unix-to-Unix Copy Program: a protocol for Unix computers to exchange files over a dial-up telephone line. In more common use to name the "faking" of an internet connection over an intermittent UUCP link -- thus, a more advanced "store-and-forward" link than FIDO.

World-Wide Web

The total collection of HyperText documents using HTML formatting. Nothing more than that: the magic (if any) is in the content...

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This is © copyright 1997 Mike Holderness; moral rights are asserted.

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