3D (three-dimensional) graphics are represented in three dimensions: width, depth, and height. This is, however, a distortion of the truth as 3D computer graphics are really a two-dimensional representation of a virtual three-dimensional world.

Access-time The time required to find a file on the hard disk, expressed in milliseconds.

Analogue A method to store information as continuously variable signals instead of electronic codes.

Animated GIF Set of pictures saved in one GIF-compressed document. When the document is opened, the pictures are shown in a predetermined sequence and speed.

Animation The very rapid sequential display of a series of slightly different images to create the illusion of movement.

Applets Very compact computer programs, written in Java, designed to be downloaded by web browsers to provide more dynamic and interactive web pages.

Assets The various data (audio, video, program-related) which comprise the contents of a multimedia program.

ATM(asynchronous transfer mode) A fast packet-switching technology, capable of data transfer rates up to 2.4 Gbit/sec. Likely to be one of the main foundations of the broadband global multimedia network that should grow from the Internet and the world wide web.

Authoring The process of constructing a hypermedia program using a software package such as Macromedia Director.

Bandwidth Defines the capacity of a communications channel: the higher the bandwidth, the greater the volume of information that can be transmitted within a given time.

Bitmap graphic Pixel-based graphics which define a display space and colour for each pixel or 'bit' in the display space. A GIF and a JPEG are examples of bitmap graphic image files.

Browser An application enabling access to world wide web pages. Most browsers allow the user to view web pages, copy and print material from them, download files from the web and navigate in it.

Browser-safepalette or web-safe palette A palette of 216 colours common to the system colours of PC and Mac, that will appear the same on both a PC and a Mac.

Cable modem Designed to use existing television cable to distribute multimedia to homes.

CD-I(compact-disc interactive) An early multimedia compact disc-based system, developed jointly by Philips and Sony.

CD-ROM(compact disc read-only memory) The compact disc format principally devoted to text and data (and occasionally audio and graphics) according to the technical specifications of ISO 9660.

CGI(common gateway interface) Program that administers interactions between web users (clients) and the HTML and other web page documents on a server.

CGM(computer graphics metafile) Vector file format.

Client A computer that requests information from a network's server.

Client/server system The organisation of a computer network whereby 'clients' can access software or documents from a server which holds the software or documents. The world wide web is based on a client/server model.

CLUT(colour look-up table) A table which assigns a discrete value to every colour available at any one time, so that graphics can be encoded quickly using these convenient table addresses rather than the less accessible 'absolute values' of the entire RGB colour range.

CMYK(cyan, magenta, yellow, black) Subtractive colour model based on the light-absorbing quality of ink printed on paper (opposite in use to RGB).

Compression Reduction of the amount of data required to recreate an original file, graphic or film. Compression is used to reduce the transmission time of media and application files.

Cookies(HTTP cookies) Information that a website puts on your hard disk so that it can recall something about you at a later time. The browser should only return this information to the same website that 'set' the cookie on your machine.

Cross-platform A term that describes a language, software application or hardware device that works on more than one system.

CSS (cascading style sheets) See style sheets.

Data Information stored in digital form.

Database A structured collection of data: information that has been organised in such a form that it can be stored, sorted, manipulated, and retrieved through a computer system.

DHTML(dynamic hypertext mark-up language) Refers to web content that changes each time it is viewed. For example, the same URL could result in a different page depending on any number of parameters, such as geographic location of the reader, time of day, previous pages viewed by the reader, profile of the reader. There are many technologies for producing dynamic HTML, including CGI scripts, server-side includes (SSI), cookies, Java, JavaScript, and ActiveX.

Digital Information represented by discrete units, usually binary numbers (0 and 1). The digitising of media elements, such as text, sound, image, animation and video, is the basis of hypermedia.

Dithering The positioning of different coloured pixels within an image that uses a 256-colour palette to simulate a colour that does not exist in the palette. A dithered image often looks 'noisy', or composed of scattered pixels.

DNS(domain name system) A 'domain name' is given to each computer or network connected to the Internet, providing an alphanumeric address that is easier to remember than a numerical (or IP) address. This address is used by the protocols that control data exchange over the Internet.

Download The process of transferring software or other digital information from one computer to another over the network.

DSL (digital subscriber line) Service available in various technologies (HDSL, SDSL, ADSL, VDSL and RDSL) with differing data rates, operating distances, and ratios between downstream and upstream speeds.

DVD(digital versatile disc) A new standard for digital-optical discs. A DVD is the same diameter as a CD-ROM (120 mm) but is double sided and stores data in two layers to give a capacity of up to 17 Gb per disc.

Dynamic data Information that changes over a period of time.

E-mail Term describing messages sent over a computer network. E-mail has become one of the most popular uses of the Internet.

Extranet A private computer network that uses Internet technology to link an organisation with its suppliers, customers and other collaborators.

Firewall A system designed to prevent unauthorized access to or from a private network. Firewalls can be implemented in both hardware and software, or a combination of both. Firewalls are frequently used to prevent unauthorized Internet users from accessing private networks connected to the Internet, especially intranets. All messages entering or leaving the intranet pass through the firewall, which examines each message and blocks those that do not meet the specified security criteria.

Fount A collection of characters in a single size and style.

GIF(graphic interchange format) A bitmapped colour graphics file format. GIF is commonly used on the web because it employs an efficient compression method.

HTML (hypertext mark-up language) The common scripting language for interchange of hypertext between the world wide web client and server. Web pages must be written using HTML.

HTTP(hypertext transfer protocol) The set of communication standards that together enable different kinds of computers to communicate with each other over the world wide web.

Hypermedia A computer-based medium combining multiple media (text, image, sound, animation and video) with high levels of user interaction and the capability to link items of information with other items within the system.

Hypertext Term originally used to describe a form of non-sequential writing. Now generally refers to computer-based text that is linked in a variety of linear and nonlinear ways. The world wide web was devised as a hypertext-based system.

Input Data, requests, choices or responses provided to a system by its users, typically from an input device such as a keyboard, mouse, touch screen or remote control unit.

Interactive Hardware and software systems which can respond to input from users: minimally, by offering a limited range of options and choices; ultimately, by providing a variety of resources which allow users to act spontaneously and react constructively, to explore a body of knowledge and create a dialogue between the user and the system.

Interface The point of contact between two systems, devices, programs, or between users and machines; and thus, the hardware and software which effect communications between two separate bodies.

Internet The global network of computers and computer networks that evolved from the US Department of Defence's Advanced Research Project Agency network, an experimental packet-switching network set up in 1972.

Intranet A private internal network within an organisation, that uses Internet technology.

ISDN(Integrated Services Digital Network) A network operated by telecommunications companies that supports a higher bandwidth than the ordinary public telephone network. ISDN can transfer data through two channels at typical rates of 64 kbits/sec. (for single channel), 128 kbits/sec. (for two channels) or up to 1.5 Mbits/sec. for video conferencing.

Java An object-orientated programming language originating from Sun Microsystems in the early 1990s. Used to develop platform-independent mini-applications (called applets) that run on a virtual Java computer (a software emulation) that can be installed on most computers. Many websites now contain downloadable applets, which may be anything from calculators to games.

JavaScript A scripting language developed by Netscape to enable web authors to design interactive sites. Although it shares many of the features and structures of the full Java language, it was developed independently. JavaScript can interact with HTML source code, enabling web authors to spice up their sites with dynamic content. It is endorsed by a number of software companies and is an open language that anyone can use without purchasing a licence. It is supported by recent browsers from Netscape and Microsoft, although Internet Explorer supports only a subset, which Microsoft calls Jscript.

Joystick A popular input device for computer games and some technical training applications which employs a short rotating shaft, grasped in the user's fist, to direct the movement of the cursor on the screen.

JPEG(Joint Photographic Experts Group) A lossy compression technique that can reduce the size of a graphics file by as much as 96 %.

Link Emphasised word in a hypertext document that acts as a pointer to more information on that specific subject.

Lossy compression A data compression technique in which some data is deliberately discarded in order to achieve massive reductions in the size of the compressed file.

Menu A list of the choices or options available to users of a computer-based system. Menus typically employ icons or pictograms, short words, phrases or abbreviations. Pop-up or pull-down menus are normally represented on screen by one word or symbol, until selected by the user, when a larger range of options is presented.

MIDI (musical instrument digital interface) Industry-standard ports which facilitate the free exchange of digital audio signals between input and output devices such as electronic instruments, hi-fi systems and multimedia players.

MIME(multi-purpose Internet mail extensions) An Internet standard for transferring file non-text-based data such as sounds, films, and images.

Modem A digital-to-analogue device that links computers to the telephone network. A modem enables digital data to be modulated so that it is compatible with the analogue signals carried by the telephone system.

MP3 A digital audio compression algorithm that achieves a compression factor of about one twelfth while preserving sound quality. It does this by optimising the compression according to the range of sound that people can actually hear. In July 1999, MP3 was the most powerful algorithm in a series of audio encoding standards developed under the sponsorship of the Motion Pictures Expert Group (MPEG) and formalised by the International Organisation for Standardisation (ISO).

MPEG A standard defined by the Motion Picture Expert Group for the compression and decompression of motion video images.

Multimedia Generic term for 'multimedia computing' or 'interactive multimedia'; the use of multiple media within a computer system or hypermedia program. Also used to describe artworks that combine several different media.

Network System that links computers and other information/telecommunications technologies by cable, wireless, or a combination of both.

Offline Devices and services which are either not connected to a central source or system or, if connected, are not active. An offline database or video editing suite is typically self-contained, with limited facilities and resources.

Online Devices or services which are in active communication with a central source or system: an online database typically draws on a large central resource which is frequently updated, an online video editing suite deploys a battery of high-quality equipment for mixing and special effects.

OS (operating system) A program that manages the resources of a computer, such as its input/output devices, memory and file retrieval. The operating system is loaded into the computer when it starts up and supervises the running of other programs and applications.

Output Data generated or processed for display on a screen, relaying through speakers or headphones, transmission to another system or network, encoding on to a magnetic disc or optical disc, or printing on paper, photographic film or other media.

Page The basic unit of the world wide web. Each page has its own URL. There is no standard length for a page.

Palette flashing Palette flashing occurs when you change the palette by remapping the colours and this causes an annoying flash of strange colours on the display. This will occur when using smaller palettes, such as 256 colours, and attempting to display a series of images with different palettes. The best method of avoiding palette flashing is to ensure that your images map to the same palette although this may compromise colour quality.

Password protection If data are sensitive then data protection requirements will be necessary when you use a network and may even be deemed necessary when you distribute offline data. Data encryption, restricted access and password protection will be considerations for your publication.

Peripheral devices Hardware devices (such as keyboards or printers) which are physically separated from a computer but integral to its operations and under its control.

Pixel(picture element) The smallest unit of a computer screen (usually a square or rectangle). The number of pixels per inch determines the resolution of a screen. The greater the number of pixels per inch, the higher the screen resolution.

Platform Delivery platform refers to the underlying hardware and operating system that the reader uses. In the case of online systems today, more likely refers to the browser or viewer being used. In some cases the delivery platform refers to a virtual machine like Java.

Plug-in A small program linked to the web browser that will increase the number of file formats that may be processed by the browser. Most plug-ins are downloadable from the web.

PNG (portable network graphics) A new open standard proposed to replace GIF. PNG has 10 to 30 % superior compression than GIF. PNG is supported by current browsers and viewers but is not in widespread use and therefore not supported by all image editing programs. The PNG standard does not support animation as in GIF.

POI (point of information)
POP (point of purchase)
POS (point of sale) Generic marketing terms to describe displays or systems which provide information, advice or advertisements, usually to the public, in a commercial environment such as a department store or shopping mall, or recreational site such as an exhibition centre or museum. For systems which promote or even sell products or services, POS is preferred in the UK, POP in the USA. POI tends to distinguish systems which are primarily educational or instructive (but which may also include, secondarily, advertising). Transactional systems can also process orders and often accept payment by credit card.

PostScript A computer language widely used in word-processing, desktop publishing and other applications where PostScript's facility to support a wide choice of founts, WYSIWYG screen displays and complex typographical instructions is particularly valuable.

RAM(random-access memory) A read-write memory device comprising myriad discrete cells with a storage capacity of one bit each. Every cell is individually addressable and capable, therefore, of supporting random access to the data stored there. Static RAM devices hold data until they are overwritten or the power is removed (e.g., if the power fails while work is in progress, any data not yet written to RAM, 'saved' or 'stored' will be lost; data already written should be preserved). Dynamic RAM (DRAM), with different storage techniques, offers greater cell density and lower power consumption but is generally slower than static RAM devices.

Random access The facility to retrieve data (rapidly and accurately) from any part of a recording.

Real time Computer processing that takes place apparently instantaneously.

Rendering The process wherein the computer interprets all the object and light data and creates a finished image from the viewport you have selected. The resulting image may be either a still or a frame in an animation sequence.

Resolution Visual or picture quality, usually measured in lines or pixels per screen.

RGB (red, green, blue) The standard encoding method for full-colour images in digital display systems, typically with eight bits of data for every level of red, green and blue that is 28 or 256 separated levels for each of the three primary signals or 16 777 216 altogether.

ROM(read-only memory) This is 'built-in' computer memory containing data that normally can only be read, not written to. It has normally been written to by the manufacturer. Data can be supplied separately to a programmable ROM (PROM) after manufacture through special programming techniques. An erasable PROM (EPROM) or electrically erasable ROM (EEROM) can be frequently reprogrammed or erased and overwritten.

RW(Read/write) Media and devices which can both record (write) and recover (read) data (and, with associated memory, store this information permanently or temporarily).

Screen resolution The number of pixels available to the screen expressed in terms of the number of pixels on the horizontal axis and the number on the vertical axis.

Search engine A program that searches documents for specified keywords and returns a list of the documents where the keywords were found. Although a 'search engine' is really a general class of programs, the term is often used specifically to describe systems like AltaVista and Excite that enable users to search for documents on the world wide web and Usenet newsgroups.

Sequential media Media that can be played in different sequences.

Server A computer that provides services for users of its network. The server receives requests for services and manages the requests so that they are answered in an orderly manner.

Set-top boxes An application that can be plugged into a television set to function as a receiver and decoding device for digital information that is transmitted by telephone, cable or satellite.

SGML(standard generalised mark-up language) A system for organising and tagging elements of a document. SGML was developed and standardised by the International Organisation for Standardisation in 1986. SGML itself does not specify any particular formatting; rather, it specifies the rules for tagging elements. These tags can then be interpreted to format elements in different ways.

Standard Protocol Formally or informally agreed technical specifications allowing different equipment or software to work together. The Internet is essentially a set of standards enabling different networks and computers to communicate with each other.

Streaming A constant data transmission technique for transferring large data files through the Internet.

Style sheets Collections of style information that are applied to plain text. Style sheets also provide broader formatting instructions by specifying values for quantities such as line spacing and left and right margins.

TIFF(tagged image file format) Originally designed as an 8 bit format for the interchange of data between graphics packages, although it has been substantially extended since its inception. TIFF is very widely supported, but portability problems sometimes occur when different versions of the format are expected.

Touch screen A screen or membrane for a video or computer monitor which typically employs XY coordinates to interpret pressure in designated locations (i.e. hotspots) as input to initiate actions or responses.

Typeface A family of graphic characters that includes many styles and sizes. (A fount is a collection of characters in a single size and style. Times and Courier are typefaces and Times 12 point italic is a fount. In the IT environment, the word 'fount' is often used to mean typeface.)

URL (uniform resource locator) The method of addressing all the resources (computers and files, websites, etc.). Most URLs contain the service, host name and directory path, separated by either a dot (full point) or a forward slash.

Vector graphics Graphics that are represented by a number of mathematical expressions.

VR(virtual reality) Simulations in which the user is immersed within a computer-generated environment. VR usually involves real time 3D animation, position tracking and stereo audio and video techniques.

Voice recognition/synthesis Computer-based systems which can interpret spoken commands (typically using keywords equivalent to the commands or options normally offered through menus or icons), and which can output data as speech wholly generated from within the system itself.

Web server A computer that delivers (serves up) web pages. Every web server has an IP address and possibly a domain name.

Window The effect or feature in which data from various sources can be displayed simultaneously in different parts of the screen, typically in rectangular boxes which can be designed, scaled, moved and manipulated in various ways, by the designer and, sometimes, by the user as well.

WWW(world wide web) A subset of the Internet, the world wide web is a hypermedia-based system that has had the most explosive growth in use of any new medium in history.

XML(extensible mark-up language) A specification developed by the W3C. XML is a pared-down version of SGML, designed especially for web documents. It allows designers to create their own customised tags, enabling the definition, transmission, validation, and interpretation of data between applications and between organisations.