glossary
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Glossary of terms ADSL Asymmetric Digital Subscriber Line. A technology allowing high speed data transfer over standard telephone lines. It is many times faster than the commonly used 56kbps modem and allows for simultaneous voice and data transfer. Typically a 2mb file download will take 9mins 18 seconds compared to 1 second for a 1.5mbps adsl connection. It is called "asymmetric" because the download speed to the subscriber is faster than the upload speed from the subscriber. See DSL and HDSL. adware A software which serves banner ads or pop ups. It is sometimes installed as freeware or shareware and is downloaded from the internet. Some adware will track your internet usage, files and software and report data back to advertisers. See Spyware. AIFF Audio Interchange File Format. An audio file format standard used for storing sound data for personal computers and other electronic audio devices. The format was co-developed by Apple Computer in 1988 and is most commonly used on Apple Macintosh computer systems. See IFF. aliasing, anti-aliasing One of the most important techniques in making graphics easy to read and pleasing on the eye. It is a way of fooling the eye into seeing smooth edged and curves when there are none. alpha Testing In software development, Alpha Testing is an early stage of testing used by in-house personnel to identify bugs. It involves systematically trying out all of the programs functions. See Beta Testing. animated GIF A GIF graphic file consisting of two or more images in a timed sequence to give the effect of motion. See GIF anonymous FTP A form of login to a public FTP system without an FTP account. The username of "anonymous" or "ftp" with user's email address as the password. See FTP. API Application Program Interface. An interface providing a set of tools, protocols and routines for building software applications. The interface provides the building blocks and a software programmer will put all the blocks together. applet A software application that runs in the context of another program, for example a web browser. An applet typically performs a narrow function that has no independent function. Hence it is an "application -let". Java Applets are used to provide interactive features to web application that could not be provided by HTML. archive A storage repository for files, data and other material to be saved and preserved. To compress one or more files or folders into a single file for backup or transport. Arpanet The Advanced Research Projects Agency Network - the predecessor of the global internet. Developed by DARPA (Defence Advanced Research Projects Agency) of the United States Department of Defence, it was the world's first packet switching network. Packet Switching is now the basis for voice and data communication worldwide, however, back in 1960's data communication was based on the idea of circuit switching as in the old telephone circuits. .art A graphics format used by AOL. ASCII ASCII stands for "American Standard Code for Information Interchange. It is the numerical representation to encode upper and lower case letters in the English alphabet and special characters. It is a seven bit code, meaning it used a pattern of seven binary digits (a range of 0 to 127 decimal) to represent each character. An extra bit is sometimes added and used for checking communication and some other device-specific functions. ASCII reserves the first 32 codes (numbers 0-31 decimal) for control characters. For example, character 10 represents the "line feed" character (which causes a printer to advance its paper), and character 8 represents a "backspace". Code 32 is the "space" character and codes 33 to 126 are known as the printable characters for letters, digits, punctuation marks etc. Finally code 127 is officially known as "delete" and means "remove the character after the cursor". See the ASCII table for more details. The most common 256 character set is ISO 8859-1 (Latin 1). ASCII art ASCII art is a medium for displaying art using the 95 printable characters (from a total of 128 characters) defined by the ASCII standard by piecing together characters. A popular simple form of this are "smileys" or "emoticons" but can be pieced together to form elaborate pictures. ASCII art is used where text can be more readily printed or transmitted than graphics or where the transmission of graphics and pictures is not permitted, for example, usenet messages and email. ASCII file Files that only use 128 characters that can be encoded with 7 binary digits. Certain internet protocols only support 7 bits such as newsgroup readers and some simple emailers. Most text files are ASCII. Files with. txt and READ ME files are almost always text files as are .ps, .tex, .hqx, .xxe and .uue. Word processed files usually contain control codes and are 8 bit encoded. ASP Many definitions - common definitions below; Active Server Pages, a web-scripting interface by Microsoft. Advanced Simple Profile, an MPEG-4 video codec profile. Application Service Provider, a business that provides computer-based services to customers over a network. ATM Asynchronous Transfer Mode. A data link layer protocol which encodes cells of data containing 53 bytes of information (48 bytes of data and 5 bytes of header information) are transferred over a cell relay, circuit switching network. Information for multiple service types such as voice, video or data is transmitted in the fixed sized cells. It differs from other technologies that use packet-switching networks and variable sized packets, such as Internet Protocol and Ethernet. ATM is connection oriented, in which a logical connection is established between the points before any data transfer actually takes place. Avatar In Hindu philosophy, an avatar refers to the incarnation of a higher being onto planet Earth. A graphic identity that you select or create as your own to represent yourself to the other party in an online community, gaming session, chat or IM (instant messaging). AVI Audio Video Interleaved. A multimedia format introduced by Microsoft in November 1992, that can contain both video and audio data in a standard 'container' that allows synchronous audio with video playback. It is considered by some to be an out of date technology but is however, still popular among file sharing communities probably because of its high compatibility with existing video editing and playback software. An AVI file is identified by the .avi file extension. B2B Business to Business. A marketing strategy involving the transaction of goods or services over the internet between businessess (as opposed to transaction between other groups, such as business to consumer - B2C). backbone The internet "backbone" refers to the main trunk connection of the internet. A collection of high-capacity data routes and core routers that carry data across countries, continents and the world oceans. Provided by network of interconnected commercial, academic and government organisations. The internet backbone has a high level of redundancy thanks to real-time routing decision making using the Internet Protocol (IP). For History, see Arpanet. bandwidth Usually measured in Herts, kiloHerts or megaHerts, bandwidth is the difference between the upper and lower cut off frequency of a communication channel of signal spectrum. In relation to website hosting, bandwidth is the amount of data that can be transferred from a webserver, measured in bytes, over a prescribed period of time. A more accurate term of bandwidth in this context would be "monthly data transfer". Web hosting companies often set a monthly bandwidth limit. A monthly limit of 500 gigabytes is not uncommon. Bcc In the context of email messages. A Blind Carbon Copy is a method of sending email's to multiple recipients in such a way that each recipient does not receive a complete list recipients. See Cc. beta testing In software development, beta testing is a stage in the development of a particular program where it is tried out to an audience similar to its intended end user, prior to the release of the program, with a view to finding bugs and errors. binary Binary is term used to describe a numbering scheme in which there are only two values for each digit: 0 and 1. The binary number system is also referred to as the Base-2 number system just as the Base-10 number system is known as the decimal number system. In the decimal number system each digit can have 10 possible values: 0-9 - this is the system we are familiar with. A term "binary digit" is shortened into the term "bit". You may have heard the terms "bit" and "byte" being used in computer terminology. As we said earlier the bit can only be a "0" or a "1" and bit are not used alone, they are bundled together in a collection of 8 bits, referred to as a "byte". With 8 bits in a byte you can represent 256 values ranging from 0 - 255. 0 = 00000000 1 = 00000001 254 = 11111110 255 = 11111111 See also CD's using 2 bit or 16 bit sampling The term also refers any digital encoding/decoding system in which there are only two possible states. binary file Binary files are files that are made up of binary digits (bits) grouped together in a collections of 8 with a possibility of 256 characters. As apposed to ASCII files made up of binary digits (bits) grouped together in collection of 7 with a possible 127 characters. Binary files usually contain bytes that are intended to be interpreted as something other than text characters. for example, video, audio, compressed files and more or less any other type of file. bit A shortened term for binary digit, the bit is abbreviated by a lower case "b" to distinguish it from a byte (B). Kbps (thousand bits per second), KBps (thousand bytes per second). bitmap A graphic image consisted of rows and columns of dots with the information for each dot, whether it is being filled or not, stored in one or more bits. For simple monochrome images, one bit is sufficient for the information required for one dot but for colour images and shades of grey more than one bit is required for each dot. The density of the dots is known as "resolution". Bit-mapped graphics are known as "raster graphics" or "object orientated graphics". Bit-mapped graphics are generally stored with a colour depth of 2 (1 bit), 16 (4 bit), 256 (8 bit), 65,536 (16 bit), 16.7 million (24 bit). The bits in brackets represent the bits of information required for each dot (pixel). A 32 bit version is used by Windows XP for its logon and theme system and uses an "alpha channel" for its transparency data. blog A shortened term for "web blog", a blog is chronological list of entries displayed in reverse chronological order. It has evolved from an online diary where people would keep a running account of their everyday activities. Modern blog software enables users to add images and links and allows visitors to leave comments. The word blog can also be used as a verb to describe the action of maintaining or adding content to a blog. bookmark Sometimes referred to as a "favourite", it is a stored web address (URL) for quick access by web browsers. A bookmark may also be the location of a document used by word processors. Boolean search Boolean search, named after Gearge Boole who first defined the "Algebraic system of logic" in the mid 19th century, allows for the narrowing down of search results by adding special terms before your search keywords, such as AND, OR and NOT. bot Bots shortened from "web robots" are software application that run automated tasks over the internet. Typically, bots are the various spiders, crawlers and worms that fetch, analyse and index information by visiting web pages by hopping from link to link from website to website at a much higher speed than would be possible by human searching. bounce A "bounce" is an automated email message from a mail system informing the sender of a delivery problem. The bounce email is sometimes referred to as a Delivery Status Notification (DSN) message. bps Bits per second Bps Bytes per second bridge A combination of hardware and software that allows the connection of local area networks (LANs). See Router. broadband Broadband is a relative terms used in the context of bandwidth. The wider the bandwidth, the greater is the information carrying capacity. A modem is able to transmit a bandwidth of 64 kilobits per second (kbits/s) over a telephone line, whereas over the same telephone line ADSL can transmit several megabits per second (mbits/s) and is referred to as broadband relative to a modem. However, a fible optic connection could be described as "broadband" relative to ADSL. browser A web "browser" is a software application that is used to communicate with web servers primarily using the "Hypertext Transfer Protocol" (HTTP), to fetch webpages enabling users to view and interact with text, images and other information. Webpages are location by means of a Uniform Resource Locater (URL) and are prefixed with http:. Browsers are able to handle various other URL types, for example ftp: (File Transfer Protocol), https: (an SSL encrypted version of HTTP). Popular web browsers include Internet Explorer, Mozilla Firefox, Safari, Opera and Netscape. bus In computer terminology, a bus a subsystem that transfers data between computers or computer components. It differs form a point-to-point connection in that a bus can logically connect several peripherals over the same set of wires. byte 8 bits of data identified by an upper case B. cache A collection of data stored in memory duplicating already stored data where the retrieval of such data would be detrimental to performance. A temporary storage area for frequently accessed data. See CPU cache. Cascading Style Sheets (CSS) A stylesheet language used to describe the presentation of a webpage. It can used to define fonts, colours and layouts of webpages. It is primarily used to separate the document content (written in HTML) from the document presentation (written in CSS). A CSS can be used by the author and the reader. Author's can provide styling information in the form of external style sheets (a separate style sheet referenced from the document), in-line style sheets (inside the HTML document defined by the "style" attribute) or embedded style (blocks of CSS code inside the HTML document). The reader or user of a document can use an override style specified by options in the web browser or by a default style being used by the browser's default presentation of elements. CSS has the advantage of holding all the presentation data for an entire website in one file. However, the interpretation of style information can be slightly different between Internet Explorer, Netscape and Firefox, so what works for one browser may not work exactly the same for another. case sensitive Upper case letters are coded differently to lower case letters and software is programmed to recognise then as the same. Certain applications are not programmed to recognise case, such as password and username applications. On the internet web addresses are not case sensitive but file names are. For example the following will always match; Whereas the following may not, depending on server type and set up. http://www.in-costablanca.com/web-design http://www.in-costablanca.com/Web-Design CERN European Organization for Nuclear Research (French - Organisation européenne pour la recherche nucléaire) is the worlds largest particle physics laboratory and was the birth place of the World Wide Web. It began as a project called ENQUIRE and was based on the concept of hypertext to facilitate the sharing of information among researchers. The first website went on line in 1991 and on 30th April 1993, CERN announced that the World Wide Web would be free to anyone. CGI Common Gateway Inteface. A protocol used for the passing of information on the internet between the web browser and webserver. See PHP. charset Shortened term from character set. A group of unique symbols used for displaying and printing. Different character sets exist for use in different languages. chat Real-time one-to one of conference conversation over the internet. One participant can type in some text to be displayed simultaneously on all the screens of the participants in the same chat. usually using the Internet Relay Chat protocol (IRC). IRC was created in 1988 by Jarkko "Wiz" Oikarinen, and the software is now available for virtually every computer operating system. CIDR Classless Inter-domain Routing. client A client is a computer system that accesses a remote system on some kind of network. client server architecture An architecture separating the client form the server implemented on a computer network. Each client and server can be described as a node. Each client can send a data requests to any of the connected servers. The server will accept the request, interptet and process the data and send it back to the client. A modern day example of this architecture is the web browser acting as client and the web server, database or mail server acting as server. This type of architecture is known as two tier. There are many different types of architecture including, peer-to-peer commonly known as P2P (each node can simultaneously act as server or client) and multi-tiered (consisting of three types of node; clients, applications servers which process data for the client and database servers which store the data for the application servers). compression A process of encoding data using fewer bits than the unencoded data would represent. A common compression instance is a ZIP file format. In addition to reducing the file size, the Zip application also acts a file archiver, storing many files in a single output file. Compression is useful to help reduce the consumption of valuable resources, such as disk space or bandwidth. Compression will only work if both the sender and receiver of the information can implement the coding. content The textual, visual or aural information on a webpage as apposed to its design and layout. cookie Sometimes known as HTTP cookies or web cookies, are small parcels of text sent by a web server to a web browser and returned back to the web server unchanged eat time it revisits the server. Cookies have been the subject of many internet myths. Despite the detection of cookies from sone anti virus programmes, cookies are, in fact, just small pieces of data unable to perform any operation on thier own. They are niether spyware nor viruses. They are used for identification, tracking and maintaining specific information about users. Shopping websites use cookies to identify and maintain data, sometime accross multiple visits, to enable the functioning of shopping carts. Cookies may be easily errased after visits from Tools menu in Internet Explorer. Browsers have settings to allow the user to not accept cookies at all (however this option may make certain sites unuseable, or restict certain functions), to prompt the user to accept each individual cookie and build of white list of accepted sites, to always accept cookies or to accept cookies except from sites that the user specifies, creating a black list. COPA Child Online Protection Agency. Passed in 1998 in the United States, a law with the declared purpose of protecting minors from harmful sexual content on the internet. The federal courts have ruled that the law violates the constitutional protection of free speech, and have therefore blocked its from taking effect. Most recently, on 22nd March 2007, U.S. District Judge Lowell. A. Reed, Jr, again struck down the Act finding that the law violates the First and Fifth Amendments of the United States Constitution. COPPA The Childrens Online Privacy Protection Act of 1998. A United States federal law applies to the collection of personal information, by persons or entities under U.S. jurisdiction, from children under 13 years of age. The Act applies to all websites and online services operated commercially that are directed to children under 13 or have knowledge that children under 13 are providing information online. copy-and-paste, cut-and-paste The action of copying or moving text, data, files or objects from a source to a destination. If the copied item is deleted from the source, it is known as cut-and-paste. The user must first highlight the subject by positioning the curser at the beginning and dragging to the end. Then, depending on the application, either right click and select cut or copy, or select edit and cut or copy from a menu, or with the selection highlighted simultaneously press keyboard ctrl and x (to copy), ctrl and c (to cut). To paste the selection position the curser at the required destination and either, right click and select paste, or press keypad ctrl and v. copyright A set of rights regulating the use of information. Quite literally "the right to copy". It protects creative or artistic work such as literature, drama, music, art, recording and broadcasts. At applies to any medium. country codes Two letter codes in the ISO 3166-1 standard to represent countries and dependent areas. They are mostly used for Internet Top Level Domains. The United Kingdom requested an exceptional reservation of .uk instead of their native .gb. The codes are also used for, amongst other things, International Bank Account Numbers, Currency codes SWIFT codes (bank identifier codes), United Nations code for Trade and Transport Locations. cracker A person who compromises the security of a system or exploites a system without permission for thier own gain (black-hat). As opposed to hackers (white-hat) who expose vulnerabilities to the general public or manufacturers. cramming The addition of charges to a subscriber's telephone bill for services that where never ordered or calls that where never made. CRC Cyclic Redundancy Check. A error detecting code used in the transmission or storage of data packets. CSS - see Cascading Style Sheets cyberspace The metaphorical space of all computing systems and networks where all communications take place. The word "cyberspace" (from "cybernetics" and "space") was coined from science fiction novelist William Gibson in his 1982 story "Burning Chrome" and later in his 1984 novel "Neuromancer". During the 1990's, Cyberspace started to be a synonym for the Internet and later the World Wide Web. cybersquatting According to U.S. Federal law, "cybersquatting" is registering, trafficking in, or using a domain name with bad faith or intent to profit from the goodwill of a trademark belonging to someone else. The cybersquatter will then offer to sell the domain to the person who owns the trademark at an inflated price. database A structured collection of data stored in such a way on a computer that specific data can be easily located or queried. See SQL datagram A term for the more commonly used "packet" (formatted block of data) in data transmission. DHTML - see dynamic HTML differentiated services Differentiated Services or DiffServ is a network architecture for managing network traffic. At present all traffic or packets, are treated the same. However, with DiffServ priority can be given to certain critical packets such as voice or video, while giving best-effort traffic to low priority non-critical packets such as file transfers or general web traffic. dither In digital photography and image processing, it is a technique to create an illusion of colour depth in images with a limited colour palette. Colours not available in the current palette are approximated by a diffusion of coloured pixels from the available palette. Digital Nervous System (DNS) DjVu A file format primarily to store scanned images allowing for high quality, low file size imaged for viewing on the internet. The technology was developed at the AT&T Laboratories in 1996. DNS Domain Name System. Serves as a phone book for the internet, translating hostnames into IP addresses. The DNS system is basically a key-word redirection service essential to the running of the contemporary Internet. domain name A name that identifies a computer on the internet. A component of the URL. A name that the DNS system uses for other purposes, for example the name after the "@" in email addresses. A product that domain name registrars provide to their customers. The most common types of domain names are memorable names that stand in for numeric IP addresses. The difference between a domain name and a URL: http://www.in-costablanca.com - URL www.in-costablanca.com - domain name in-costablanca.com - registered domain name DOS Disk Operating System. A term that commonly refers to the operating systems that dominated the PC/IBM compatible market between 1981 and 1995 (or if one includes the Windows 9x operating systems, up to 1990). DoS Denial of Service. An attack on a server of a website of service intended to make the resource unavailable by sending numerous packets requiring a response. It has the effect of slowing down the site or making it unavailable depending on the level of attack and server resources. download To download is to receive data from a remote or central system. A download is a file located on a server that is made available for downloading. To download and save data is referred to as a download but when a server restricts the saving of the data it is referred to as a stream. See upload. DSL Originally DSL stood for Digital Subscriber Loop, although in recently it has taken on a more marketing-friendly name of Digital Subscriber Line. DSL works by splitting the convention telephone line into two "bands". The ISP data runs at a high frequency with a filter on the line to filter out the low frequency telephone signal. With Asymmetric DSL (ADSL) the download speed is higher than the upload speed and with Symmetric DSL (SDSL) both the download and upload speed are equal. DTD Document Type Definition A term used to describe a document or portion of document that is authored in the DTD language. A DTD is associated with a XML document by a Document Type Declaration. A tag near the start of the XML document. Example - <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> Dublin Core The Dublin Core Metadata Element Set is a standard for cross-domain information, a common semantic building block of Web metadata. The simple Dublin Core Metadata Element Set (DCMES), consists of 15 broad metadata elements.
The Dublin Core Metadata Initiative is an organisation providing an open forum for the definition of semantics, both for subject-specific and general description elements. Dymanic HTML (DHTML) A combination of technologies including static markup language (HTML), a client-side scripting language (javascript), a presentation definition language (CSS) and the document object model (DOM). These technologies are used to make webpages interactive and animated. A DHTML webpage is any webpage in which the client-side scripting changes values in the presentation definition language, which has the effect of altering the look and function of an otherwise static HTML webpage, after the page has been loaded. Not to be confused with a dynamic web page which changes on every page re-load by virtue of client-side scripting and server-side scripting. See PHP & Perl. e- (prefix) The prefix "e-" is often used for the computer related counterpart of an pre-existing product or service, standing for the word "electronic". For example, e-mail (electronic mail), e-commerce (electronic commerce), e-banking (electronic banking), e-book (electronic book) and e-business (electronic business). Easter Egg (virtual) A hidden message or feature built into a program activated by an undocumented series of keystrokes, mouse clicks or commands. E-mail, short for electronic mail, is a method of composing, storing, sending and saving messages over electronic communications systems. E-mail predated the internet and was in fact crucial in the creation of the internet. The spelling of this term is often disputed and is often seen as e-mail or email, without the hyphen and in some case, just mail. Because internet e-mail has no provision to authenticate the sender, it is open to abuse, commonly called spamming typically which false From addresses and routing. Emoticon A fusion (portmanteau) of the words emotion and icon and is a symbol or combination of symbols used to convey emotional content in the written form. Examples of text based emoticons include: :) :-) ;) :( In web-forums and messaging, text emoticons are usually automatically replaced by small graphical images. See also Smileys Ethernet A family of local-area network (LAN) technologies. Developed by Xerox PARC in the 1970's as an experimental co-axial cable network running at 3Mbps. Success of the project attracted the attention in the industry and in 1980 led to a joint development led by a three-company consortium: Digital Equipment Corporation, Intel Corporation and Zerox Corporation, of the 10Mbps Ethernet Version 1.0 Specification. Extranet A private network using Internet Protocols to share a pre-defined part of an organisation's information with suppliers, vendors, customers or other businesses. Extranet can be part of a company's Intranet that is extended outside to other companies, typically over the Internet in isolation from all other Internet users. FAQ Frequently Asked Question(s). A list of questions and answers commonly asked pertaining to a particular topic. Today, lists of questions and answers on a particular topic are called FAQ's regardless of whether the questions are actually frequently asked, if asked at all. The FAQ's may be based on anticipated questions. firewall A Software or Hardware device used to regulate (permit, deny or proxy) the flow of traffic through a computer network relevant to level of trust. An example of this is the Internet with no trust and an internal network with a zone of trust controlled by a configured Firewall at the point of entry to the internal network. flame, flaming Flaming is a message sent over the internet, usually in the social context of IRC (Internet Relay Chat) or message board with deliberate intent to insult. flame war. Two or more people exchanging insults in public messaging sometimes with a view to disrupting the flow of normal messaging. frames By using frames, a website can be divided up into several different frames each holding its own HTML. The frames can be scrolled, styled and hosted independently of each other and can be displayed on the same page. However, some browsers do not support frames. Frame Relay Freeware Copyrighted software available free of charge for an unlimited time. Freeware may have use restriction attached such as for personal use, individual use, non-profit use, non-commercial use or academic use. See Shareware. FTP File Transfer Protocol. A method of transferring data between one computer to another over the Internet or network. The protocol involves two computers, a client and a server and runs exclusively over TCP. The FTP server typically listens for incoming connections on port 21 from TCP clients. Read more on FTP here. GIF Graphics Interchange Format. An image format introduced by Compuserve in 1987, comprising of an 8-bit-per-pixel bitmap image. The format has a palet of 256 distinct colours from the 24-bit RGB color space and support animation with the 256 colour palet available for each frame. Because of the 256 colours available it is unsuitable for reproducing colour photographs but is well suited to graphics images and logos with solid areas of colours. It is a compressed format and uses the .gif extension. GPF Most users of Windows will at some point have encountered General Protection Fault (GPF) and looks something like this, "This program has performed an illegal operation and will be shut down". The cause can be because of a program attempting to access a portion of memory that should not be accessed because it is reserved - the result is a crash. grep griefer GUI A Graphical User Interface as apposed to a Command-Driver Interface allow the user to take advantage of the computer's graphics capabilities through direct manipulation of the graphic elements, typically with the aid of a pointing device, such as a mouse or trackball. A example of a GUI is the Windows Operating System. GUID Global Unique Indentifier A widely critisised 16 byte (128 bit) number generated by a Microsoft program. The critisism stems from the fact that the GUID is a privacy hole as the source of the document or the computer or network or user can be traced back to the computer that generated it. The GUID is one of the elements which is stored as a cookie when one connects to an Internet website. Hacker The term originally referred to a person who enthuiastically explores a program to stretch its capabilities and may uncover weaknesses and vunerbilitites to the advantage of the program developer. However, recently the term referres to a malicious medler who explores the program with the intent of steling sensitive information of corrupting the program. See Cracker. Hertz, Hz. The Hertz, named after the German physicist Heinrich Hertz is the Internation System of Units (SI) base unit of frequency, originally called cycles per second (cps). One hertz is one cyle per second (cycle/s or s-1). It is sometimes referred to as inverse seconds or reciprocal seconds. As with all SI unit, Hz can be prefixed: kHz (kilohertz, 103 Hz) MHz (megahertz, 106 Hz), GHz (gigahertz, 109 Hz) and THz (terahertz, 1012 Hz). It can be said that a clock ticks at 1Hz and the human heart beats at 1.2Hz. hex, hexadecimal A base-16 number system. A numbering system containing 16 sequential numbers as base units (including 0) before adding a new number for the next number, usually written using the symbols 0-9 and A-F. Its a convenient way to express the binary system in an easier to read format. Hexadecimal numbers have many uses in computer programming and are used in the RGB (red/green/blue) colour coding for the HTML in webpages and are prefixed by "#", example, #FFFFFF (white). See Web Colours. hit A request to a web server for a file. Every file request is recorded as a hit, however one page does not equal one hit as webpages are aften made up of several files. Hit are often used incorrectly to promote a website's traffic, but because one page load can request several images and files all recorded as individual hits, the hit count will be misleading. A more reliable method to record traffic is to record page views. Hits can be used to monitior or evaluate server loadings. Home page The home page or homepage is the file that automatically loads by default when no html filename is listed. It the page that loads when website users click the "Home" link. It will usually have the name index.html, index.php or home.html. Home page can also refer to the personal webpage or website of an individual. hop In networking terms, a packet of data "hops" between one router to the next until it reaches its destination. In telecommunications technology, a radio wave will leave the earth hit the ionosphere and return to earth. Each reflection from the ionosphere is one hop. HTML Hypertext Markup Language. The markup language used to code webpages consisting of labels surrounded by angle brackets call tags. The tags are used to describe the structure of text-based information by denoting text to be displayed as headings, paragraphs, to embed imaged, to display tables and forms etc. Files written in HTML end with .html or .htm. http Hypertext Transfer Protocol is request/response communications protocol used in the World Wide Web (WWW) and Intranet between the user agent (the web browser or spider) and the origin server (web server), which stores the resources (webpages made up of HTML files and images). The http server listenes for a request message, usually on port 80, from the user agent and sends the requested file. Rescourses that can be accessed by http are identified using Uniform Resource Locatotors (URL's). See URL's and Hyperlinks. Hub A device for connecting multiply Ethernet devices together enabling them to act as a single segment. USB Hub. A device that allows the connection of multiple USB devices to be connected to single USB port. They can be bus-powered or self-powered. A bus-powered hub draws its power from the computers interface whereas a self-powered hub takes its power from its own power supply. The draw back to a bus-powered hub is that many devices requires more power than the computer's interface can supply and will only work with a self-powered hub. Sharing Hub. A device working the opposite of a USB hub allows several computers to share a single peropheral, albeit not a same time. They can manual (a simple switch) or automatic (sensing which computer requires the peripheral) hyperlink A navigation element in a webpage, usually underlined or coloured text that sends the user to another resource when clicked. The resource may be within the document, a different document within the website or to another seperate website. A hyperlink may also be in the form of a graphical element such as a button or image. Hyperlinks are the foundation of the World Wide Web. Links are tags in HTML code using the <a> (anchor) element. hypermedia An extension to hypertext. hypertext Text on webpage that when hovered over or clicked performes various dynamic function. For example, a bubble of descriptive text, or a video launch. image map A HTML term referring to an image that is broken down into smaller areas by coordinates in order to hyperlink the areas to various destination. IMAP The Internet Message Access Protocol (sometimes called Internet Mail Access Protocol) is an internet protocol that allows for access to electronic mail on a remote server. IMAP4 (the current version) and POP3 are the standard protocols for email retrieval while SMTP is the standard for email sending. Email messages are sent to the email server and stored for later retrieval. The user then sends a request to the server by using either a web browser or an email client such as Outlook Express, the server listenes for requests on port 143 and responds by sending the emails to the user. |
