Absolute URL A path name to a resource on the Internet that gives the full address of that resource. See also Relative URL. Account Lockout The practice of terminating a connection to a password protected account if someone tries unsuccessfully to access the account more than a certain number of times. Active partition The section of a disc that contains files necessary to boot up the computer. Most discs do not have active partitions. ActiveX A type of program developed by Microsoft that sits within a web page and gives added control over that web page. Adapter A device used to connect two different or dissimilar systems or connections, such as two different types of cable. Advanced Research Projects Agency ARPA An organisation developed in the United States to co-ordinate research projects in defence and academic institutions. Advanced Research Projects Agency Network ARPANET A network developed by ARPA to allow researchers at different institutions to communicate with each other. The forerunner of the Internet. Antivirus software Software designed to detect and destroy viruses on computer systems. Applet A small program written in Java that sits embedded in a web page. Application Programming Interface API The complete set of functions and calls that allows developers to use a programming language. Application Service Provider ASP An organisation that provides services over the Internet to those who would otherwise have to provide them on their own servers. Application-level gateway A firewall component that inspects packets on the Internet at the user-level. Assignment Attaching a particular resource to a particular task. Assumption This is a statement or situation that is taken to be true during the completion of some project. Assymetric-key Encryption Encryption of a message or file that uses one key to encrypt the message and a different one to decrypt it. Attachment A file that is sent as an accompaniment to an E-mail. Attenuation The decrease in strength of a signal as its distance from its source increases. AU A sound file format that is used predominantly by UNIX computers. Audio Interchange File Format AIFF A file format developed by Apple Computers for high-quality sound. Audio Video Interleave AVI The standard file format for video files on the Internet. Authentication The process of verifying the identity of a user or the source of a communication. Back end A general term covering all the systems that process and provide data as a result of requests by a client computer. Backbone The highest level of the Internet. A large-scale network to which smaller networks are connected. Bandwidth The rate at which information can be transmitted across a connection at any one time. Baseline The performance level of a network under normal circumstances against which its performance is measured. Bastion host A server that hosts several components of a firewall. Binary file A file in which the data is stored in the form of ones and zeroes. Blackhole list A list of IP addresses that are known to send out spam. Block-level element A tag in HTML that contains text or other level elements within it, such as <p> ... </p>. Blog Short for "weblog", a blog is a collection of personal thoughts and opinions on a web site, rather like an online diary. Boolean operator An operation such as AND or OR that joins two true/false conditions to produce a result that is true or false. Bottleneck A blockage or a queue in a data transmission path that causes the data traffic to slow down. Browser E-mail An E-mail service that is based on a remote server and accessed via web pages, such as Hotmail. Buffer An area of memory into which data can be loaded and kept temporarily until an application is ready to receive it. Bus A series of parallel wires that form the connection between two parts of a system, such as address bus and the data bus that link the CPU in a computer to its memory. Business logic The code, usually written in SQL, that formulates relationships between data in a database. Business-to-business B2B Commercial transactions between two companies over the Internet. Business-to-consumer B2C Commercial transactions between a company and members of the public over the Internet. Byte A unit of memory storage equivalent to 8 binary digits ("bits") Cable modem A device that modulates and demodulates data allowing it to pass from one type of cable to another. Callback A communication from a remote system in response to a client system logging on in order to authenticate the client's identity. Carrier Sense Multiple Access/Collision Avoidance CSMA/CA The method used by IEEE 802.11 wireless standard and Apple LocalTalk to access a LAN. Avoid packets colliding on a network. Carrier Sense Multiple Access/Collision Detection CSMA/CD The method used by Ethernet systems to access a LAN. A test packet is placed on the network to see if the network is busy. Cascading Style Sheets CSS Instructions to define the appearance produced by HTML tags in a web page, whose properties are "inherited" by the tags automatically. Channel The cable or connection joining two communicating systems. Character set A list of permissible characters (letters of the alphabet, digits, punctuation symbols etc.) that can be used in a particular communication. Circuit-level gateway A component of a firewall that alters packets being placed on a network using the OSI model. The packets are rewritten so that they appear to have originated from the firewall. Client A system requesting a service from a server computer. Client-side script Web page instructions that are carried out by the Internet browser on the client computer. Cluster A group of sectors on a computer disc. Clustering The fact that multiple systems can act as a single host. This gives flexibility during times when network demand is high. Coaxial cable Also known as "coax", this is cable in which the signal is transmitted down a metal core and a metal sheath surrounding it acts as the earth connection. Codec An algorithm used to compress video signals before transmission and decompress them on the client computer. Common field A field representing the same piece of information in two different database tables. Common Gateway Interface CGI A program that connects web sites to software applications so that the application can process data submitted by a user to the site. Completely Automatic Public Turing Test to Tell Computers and Humans Apart CAPTCHA A test to prevent computers from automatically signing up for usernames and passwords on password-protected systems. Concurrent Versions System CVS A tool that allows a team of software developers to track different versions of a project and to merge sections of code on which they are working independently into a unifed whole. Constraint Any circumstance that limits the options of a software developer. Cookie A small file created by a web page on a user's computer that contains information supplied by that user, such as services requested or browsing habits. Customs Habitual ways in which actions are carried out. Daemon A program on a UNIX system that activates when the user logs on and stays in the background until it is needed. Data Information, in particular information in electronic systems. Data Source Name DSN A text string that a program uses to refer to a data source (such as a the name of a table). Database Information organised into records, which are grouped together into tables. Database administrator The person in an organisation in charge of maintaining databases and ensuring the integrity of the data they contain. Database Management System DBMS A program or suite of programs that access and maintain the data in databases. Dead link A link to a resource on the Internet that does not exist (e.g. a link to a non-existent page). Decryption The process of translating a coded message back into plain language. Deep URL A web address that extends beyond the domain name into the file structure of a web site, and refers to a particular page. Demand priority A system used by hubs on 100VG-AnyLAN systems to rank requests for transmission according to their priority. Dictionary program A program used by hackers to break into systems that tries a stored list of common passwords. Digital certificate An electronic document that authenticates the identity of a user, issued by a recognised certificate authority. Digital signature A text string that can be attached to messages to authenticate the sender. Digital Subscriber Line DSL A high-speed connection that communicates entirely over digital networks. Direct Memory Access A method by which a system communicating with a computer can access the computer's memory without needing to access its central processor. Disk cache A section of memory that is used to hold copies of files from a disc that are used frequently. Dithering A process by which relatively few colours can be used in combinations to give the illusion of many more colours. Document Type Declaration A tag at the start of an HTML, XHTML or XML file that specifies the scripting rules to which the file adheres. Document Type Definition A set of rules in a text file that specifies the tags and attributes for a web page or XML document. Domain name The main part of the name of a web site e.g. in the site www.mysite.com, the domain name is "mysite". Domain name server A server that translates domain names from their text representation into an IP address. Domain name space The three-level system of domain names, consisting of root-level, top-level and second-level domains. Dynamic Applying to any aspect of networking that is not predetermined. For example, dynamic routes can be changed by routers in order to maximise the efficiency of the network. Dynamic HTML A version of HTML that gives exact control over the appearance of a web page and allows dynamic updating of the site's contents. Electronic commerce E-commerce The practice of buying and selling using the Internet. Electronic Data Interchange EDI The interchanging of documents in a standard form between computers. E-mail client A program that resides on a client's computer to handle the sending and receiving of E-mails. Emoticons Small pictures or combinations of characters included in E-mails to indicate the author's emotions, e.g. :-) for happy, :-( for sad. Emulator A program that simulates the running of another programming environment, e.g. Java programs are written to run on top of a Java emulator, itself running on the host computer. Encapsulated Postscript EPS A data format based on the Postscript language used by printers which allows pictures to be included in a Postscript file. Encryption The process of translating a plain-text message into a coded form for security reasons. Event handler A program or section of a program that deals with external events that may happen such as button clicks. Event-driven Referring to programs that execute code only in response to external events. Extensible Hypertext Markup Language XHTML The current standard language for creating web pages, obeying the strict rules of XML. Extensible Markup Language XML A tag-based language used to describe data to web pages. Extensible Stylesheet Language XSL A language used to specify the screen layout of XML files. Extranet A network that is internal to an organisation to which access is also granted to a few privileged outside users who have usernames and passwords. Field A place in a database where a single piece of information about a single record is stored. File Transfer Protocol FTP The set of rules that govern the basic transfer of general data files across the Internet. Firewall A suite of programs that restrict the traffic to and from a computer on to and off the Internet. It prevents undesirable web pages and malware from getting through to the computer. Fixed-width font A character set in which each character is padded out with white space horizontally so that they all take up the same width. Foreign key A field in a database table that is linked to the primary key in another table through a relationship. Frame A section of the screen in a web page that is subdivided into rectangular regions. The contents of this region can be altered independently of the others. Frameset document A file that controls how different frames are displayed on the screen in a web page that is subdivided into frames. Front end A computer that a person uses to send a request for processing to an extended system. Fully Qualified Domain Name FQDN A complete web address giving enough information for it to be decoded to a unique IP address. Gantt chart A chart outlining a planned timetable for tasks in a project showing when each is due to be started and completed. Gateway A node that acts as a connection between one network and another. Gnu Privacy Guard GPG An open-source version of the PGP encryption system that uses algorithms that are not proprietary. Graphical user interface GUI The part of a computer program that displays its output in graphical form, such as moving icons, and accepts input to the program using a mouse pointer. Hacker A person who attempts to gain access to a computer system without any authorisation and using secretive methods. Hash A number that is produced when a hash-algorithm is applied to a message. Also known as a digest. Hash encryption The process of applying a one-way hashing algorithm to a message to produce a hash (or digest) that cannot be decoded. Header The first part of a data packet sent across the Internet. It contains information about the destination that the packet must reach, its order in the sequence of packets etc. Help desk technician A person responsible for helping computer users with technical programs with their computers. Hexadecimal A number system based on the number 16; counting in base 16. Home page The page of a web site that is the first to appear when the site is visited. Hop The direct connection between one node and the next in a network. Used in counting how many steps are necessary to cross the network from source to destination. Host A computer on a network that can be used to provide information to another computer on the network. Hosts name A server on a network that translates all the names of the hosts on the network into IP addresses. Hub A node on a network that controls the flow of traffic to other nodes. Hyperlinks A piece of text or image in a web page that acts as a connection to another web page or other resource when the user clicks on it. Hypertext link The underlined text on a web page that the user can click on to navigate the hyperlink. Hypertext Markup Language HTML The set of tags that are used to control the layout and operation of web pages. Hypertext Transfer Protocol HTTP The set of rules that control the delivery of web pages from a server to a client computer over the Internet. I/O address A location in a computer's memory that corresponds to an input or output device. The computer corresponds with the device by reading or writing data to and from the address. Illicit server An example of malware that installs itself secretly on a computer and allows a hacker to control the computer without its owner's knowledge or consent. Image map A section of an image displayed on a web page that responds to a mouse click. It usually acts as a hyperlink to another page. Index A list in a database that lists all the unique records in a table. Information Technology IT The study of how human users interact with computer software and how they interact with each other. Infrared Electromagnetic rays, similar to light rays but beyond the range of human eyes, used to communicate wirelessly with electronic devices. Inline images Images encoded into web pages. Instant Messaging IM The practice of sending a message over a computer network to a user who is logged on to another computer on the net. The user is informed immediately that a message has arrived. Integrated Services Digital Network ISDN A high-speed digital connection that connects users to the Internet. Interactive Applying to computer programs that allow the user to issue commands and get feedback in real time. Interface The part of a computer program or system that connects with some other entity, such as a user, a network or another computer system. Internet The collection of networks to which anyone with the correct hardware and software can connect. The global network formed from a vast number of smaller networks being connected. Internet Control Messaging Protocol ICMP A protocol used to determine whether a computer can communicate with the Internet. Internet Messaging Access Protocol IMAP An advanced protocol used by E-mail clients for incoming messages, allowing features such as multiple mailboxes etc. Internet Protocol IP The set of rules that control how the packets forming an Internet transaction are routed across the Internet. Internet Service Provider ISP A company that allows users to connect individual computers to the Internet. Interoperability The ability of two different systems to work together and communicate. Intranet A network that is private to an organisation that can be accessed only by members of that organisation. Interrupt Request IRQ A signal to a computer's processor from an external device in order to make it suspend its current program and attend to the device. IP address The unique numerical address assigned to any computer or peripheral connected to the Internet. IP security IPsec A protocol used for encryption and authentication over the Internet. Java A computer language based on C++ use to create applications and applets that can be incorporated into web pages. Java Virtual Machine JVM An emulator that allows computers to run Java applications and applets by interpreting the compiled Java code. JavaScript A language embedded within the HTML code of a web page that allows the page to be interactive with the user. Junction table A table in a relational database that allows many-to-many relationships between tables to be established by linking two one-to-many relationships. Kerberos A system of communication between parties whereby each party remains anonymous, being known only to a trusted third party. Kernel The central part of an operating system that contains its most basic functions. Key A number used to encrypt and decrypt messages. Keyword One of a list of special words that make up the instructions in a computer language, e.g. the word "while" has a special meaning in JavaScript programs. Layer 1 switch A mechanical switch that corresponds to the lowest level in the OSI network model, that of the basic cables and connectors. Legacy model A system or protocol that is out of date, but is still catered for by later systems as many computers still use it. Lightweight Directory Access Protocol LDAP A protocol that allows users to access Internet-based lists of resources or people, similar to looking up a name in an online telephone directory. List server A server that maintains communications between members of a list server group. Listserver group The members of a group who send and receive communal messages via a list server. LiveScript The predecessor to JavaScript, developed by Netscape. Local Area Network LAN A network that is limited to a small geographic area, and that is usually owned by a company or organisation as opposed to being rented. Lossless compression Reducing data to a more compact form in such a way that the original data can be reconstructed perfectly. Lossy compression Reducing data to a more compact form in such a way that the original data cannot be reconstructed, but its quality is not materially affected. Usually used to reduce the file size of images without affecting image quality. Mail Delivery Agent MDA Program used by an E-mail client to send messages over the Internet. Mail User Agent MUA A messaging component that acts as a stand-alone program on a computer. Mailing list server Server that maintains lists of E-mail addresses to which bulk E-mails are sent. Malware Software designed to cause harm to a computer system and which runs without the user's knowledge or consent. Many-to-many relationship A relationship in a relational database in which several different values in one field of a table can be associated with several different values in a field in another table. Markup language Any one of a variety of languages used to construct web pages and determine their appearance. Media A general term for the different ways in which data is transmitted from one system to another. Media Access Control address MAC The physical address of a device on a network, as opposed to its IP address. Message Transfer Agent MTA A program responsible for delivering and receiving E-mail and for putting received mail in the correct inbox. Meta search engine A search engine that attempts to determine the nature and contents of a web site by examining its <meta> tags. Meta language Any language used to define or describe the rules of another computer language. MIME type The description of a file attached to an E-mail in two parts, where the first part describes the general file type and the second part gives a specific sub-type, e.g. "text/plain" or "image/gif". Modem Short for modulator/demodulator - the device that converts a digital signal to an analogue format suitable for transmission along connections such as phone lines. Motherboard The most important circuit board in a computer system, on which the CPU and other components are placed. Moving Pictures Experts Group MPEG The committee that designed the standard formats for video and sound files. MPEG-1 Audio Layer 3 MP3 A standard proprietary format for sound files developed by the Moving Pictures Experts Group. MPEG-2 The current standard for compressed video files. Multipurpose Internet Mail Extensions MIME The protocol that allows E-mail programs to associate different file types with different applications (e.g. .doc files with Microsoft Word). Multi-station Access Unit MAU The hardware device that allows stations to be connected to a ring topology network. Municipal Area Network MAN A network that covers an area the size of a town or city. Musical Instrument Digital Interface MIDI A system of encoding music electronically using a standard set of rules so that it can be played by a wide variety of devices. Narrowband A set of frequencies that have been set aside for wireless communication. National Science Foundation NSF A branch of the American government that promotes science and engineering. Needs analysis The process of determining the requirements of a customer and developing a computer system to meet those requirements. Network Two or more computers connected in such a way that they can communicate with each other. Network Address Translation NAT The process of hiding the IP addresses of computers on an intranet to external systems by translating them into different addresses. Network engineer The technician responsible for maintaining and upgrading a computer network. Network Interface Card NIC A circuit board that fits in a computer giving its physical address on a network. Network News Transfer Protocol NNTP A set of rules allowing computers to communicate with newsgroups. Network Operating System NOS An operating system designed to control a computer network Newsgroup An application that allows users with a shared interest to post articles, opinions, questions and answers on that interest on a shared space on the Internet. Node A computer or resource on a network. Non-repudiation The principle that neither of the two parties to a transaction or a sent message can deny that the transaction took place or that the message was sent. Object A part of a web page that contains data and can have a name and properties. Object-based This applies to programming languages in which data is organised into objects. However, unlike object-oriented languages, there is no inheritance. Object-oriented Applying to any computer language in which data is arranged into objects that communicate with each other. Objects are placed in a hierarchy of classes, so that each class can inherit properties from classes higher in the hierarchy. Object-oriented programming OOP Any computer language based on communicating objects. OCx Optical carrier levels which are used to define the transmission speeds in SONET/SDH One-to-many relationship A relationship between two tables in a relational database in which the primary key of one table is associated with a non-primary key of the other table. One-to-one relationship A relationship between the primary key fields of two tables in a relational database. Online service E-mail An E-mail client program that comes bundled with software from an Internet Service Provider (such as AOL). Open Buying on the Internet OBI A common format that businesses use to exchange data. Open source A programmer providing access to the source code of a program free of charge so that developers can improve it. Open System Interconnection Reference Model OSI/RM The 7-layer model describing a standard structure for transmission of data over a network. Order Tracking The process of recording the progress of a customer's order through an online purchase. P2P A peer-to-peer network connected to the Internet. Packet A small piece of a data message that is transmitted over a network. Packet sniffing A technique used by hackers to intercept packets travelling over a network. Password sniffing A technique used by hackers to intercept passwords being sent across a network. Patch A small section of computer code that can be downloaded from a web site to correct a fault with a program. Patch panel A series of sockets that can be used to switch manually between incoming communications and outgoing communications. Peer-to-peer network A network in which all computers have equal status. There are no dedicated server computers. Peripheral port A socket on a computer in which peripherals such as printers are plugged. Permission bit A binary digit associated with a file that indicates whether a user can read it, overwrite it or execute it (in the case of a program). Permissions Pieces of information associates with programs and files on a network that specify which users can access them. Personal Digital Assistant PDA A small portable computer designed to keep track of personal information such as appointments and contact details. Personal Information Management program PIM A program that organises contact details, engagements and appointments. Planned maintenance Any maintenance such as upgrading hardware or installing software that may be scheduled in advance. Plug-in A small program such as Flash that must be downloaded in order to make full use of the resources on some web pages. Point-to-point Protocol PPP A set of rules that allow a computer to connect to the Internet over a telephone line. Point-to-point over Ethernet PPPoE A set of rules that allows an entire Ethernet network to be connected to the Internet. Point-to-point Tunnelling Protocol PPTP A protocol that is used to extend a network securely over the Internet using remote servers. Pop-under Window A window that appears automatically underneath another web page when something triggers it (such as a mouse click) and only appears when the original page is closed. Pop-up Window A window that appears automatically on top of another web page when something such as a mouse click triggers it. Port A logical connection to an operating system through which information passes when the client computer communicates with a network. Portable Document Format PDF A standard document format developed by Adobe to allow documents to be published on the Internet. Post Office Protocol POP A set of rules that deal with the delivery of E-mail. The current standard is POP3. Presentation responsibilities This refers to the way in which data is presented to the user on the screen, such as data entry forms. Pretty Good Privacy PGP A program developed by Philip Zimmerman to encrypt messages such as E-mails using strong encryption and assymetric keys. Primary key A field of a table in a database that is used to identify records in the table uniquely. No two records in the table may have the same values in the primary key field. Print queue The list of files waiting to be printed on a printer, usally one shared by various computers on a network. Project This is a list of tasks that have to be finished on a certain schedule and within a certain budget. Project management The process of determining the goals of a project, scheduling the tasks required to carry out the project and then ensuring that the tasks are completed satisfactorily. Project schedule The list of subtasks that form a project together with the dates by which they must be completed. Proxy server A server connected to a network gateway that redirects requests to computers on that network by rewriting incoming IP addresses. PS/2-style connector A type of miniature DIN plug with six pins. The name comes from the fact that they were associated with the IBM PS/2 range of computers. Socket The end point of a logical connection usually including the TCP or UDP port that is used and the IP address.