Internet General Glossary Communications and Information Technology

Internet General Glossary sections: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Other glossaries and link pages
[General glossary ] [Computer terms] [Network terms] [Program terms] [Java Fact File] [Useful sites] [GNVQ Glossary]

ANONYMOUS FTP:an FTP protocol that allows a guest user to log onto a remote FTP server, searching and accessing it's files.  Restrictions can be applied to prevent the guest accessing directories/files, making them read only etc.
see  protocols

APPLET:  A Java program that is created to run in the HTML code on a Web page page.  JAVA Applets are self contained programs which download to a client computer to run client-side, not as compiled programs running on server-side.  Servers can push programs (Push Tool) to clients to develop true distributed processing.  (slow downloads/screen refreshing).  Applets are not the same thing as a Java application as applets can only run in a web page where as Java applications can run by themselves on an operating system.  Neither is it the same as JavaScript whos code is embedded into the HTML, Applet code is contained elsewhere and pointed to from within the HTML code.   see JavaJavascriptHotjavaJava factfile No.1

ARCHIE is a system that lets you search for files on FTP sites that allow anonymous logins. see search engines

ASCII: (American Standard Code for Information Interchange) a basic (7-bit code) text format that most computers read.
.

BAUD: a measurement of the number of changes per second that occur in transmission.

BBS:(Bulletin Board System)an electronic notice board where the user can post public notices.

BINARY TRANSFER: the transfer of data between computers; often used to FTP files that contain graphic images.

BROWSER: graphical interface software that allows the user to look at and interact with Internet files.  Interprets the HTML / JAVA files to give the required page layout.  Users can jump rom site to site by clicking on hypertext links.  Examples of browsers are Netscape's Navigator, MS Internet Explorer and Mosaic.  A browser is really a group of small programs that enable the user to view hypertext pages etc.

BYTE CODE the code produced when compiling Java programmes,  this is a neutral form of code that can be finally compiled to the format required by the specific platform that intends to run it.  This means that Java programmes are platform independant.  The programme that carries out the final compilation is called Java Virtual Machine (JVM).  see JVMJavaJavascriptApplets

C a procedural languagedeveloped to write the Unix operating system,  from a preceding language called 'B' Not good at handling strings - too complex - poor error detection/debugging. see languages

C++ Object oriented language based upon 'C' the name is supposed to be derived from the 'C' where ++ means INC1.  It is intended to mean "one better" than 'C' (handles strings better than C) see languages

CERN: The Conseil Europeen pour la Recherche Nucleaire. European particle physics laboratory that was the birthplace of the World Wide Web in 1989.

CGI (Common Gateway Interface): allows the Web to become alive and interactive.  Task rather than process oriented, run to do the job and then closed. Browsers and Web Servers communicate using HTTPbut a web server doesn't remember what you are doing in between visits, no matter how many times you access it.  CGI programs are simple things often written in C or PERL .  Programs are often called scripts (the first programs were written using UNIX shell scripts).  Both interpreted and compiled programs are referred to as scripts.

CGI Scripts: these are separate programs used to carry out a particular function.  (e.g.. guest book, counter etc.).  The files have to be kept somewhere and the most common place on the Server  is in a cgi-bin directory.When connecting to an ISP service provider the user is often offered free web space to design a web site.  Server-side cgi programs are available and are contained in directories which the user does not have rights to write to.  Personal cgi-scripts cannot be saved and existing ones cannot be altered.  This is to prevent malicious script being stored on a web server.  see  languages

CHECK BOX is a window control feature that allows a user to make one or more choices (a check mark appears in a box when selected).  For single selections only see radio buttons.

CLIENT: a computer connected to a server that receives information.

CLIENT PULL a method whereby a Web client can request the Web server to send it a particular site of data.  see also  server push

CLIENT SIDE refers to programs stored and run on the client computer rather than from the server storage area.  JAVA, JavaScript/VB Script run client side.  JAVA runs in the clients browser.  For JavaScript/VBScript the browsere becomes the program's interpreter. See server-side, languages

COMPRESSION:reducing a file size by a variety of techniques. E.g.. GIF, ZIP, JPEG files.

DAEMON: Unix terminology for a program that is always running on a server machine, waiting for requests for a particular service.  E.g.. an FTP server daemon sits and waits for an FTP client to connect and request files.

DIGITAL CERTIFICATE: in the common security standard for on-line transactions called SET (Secure Electronic Transactions), a Digital Certificate is issued by banks to each patron/merchant to identify them as valid transactors.

DLL (Dynamic Link Library)

DNA (Domain Name Address): the textual format of an address (WWW.btinternet.com) as opposed to a numeric IP address (193.61.111.250).

DNS (Domain Naming System) was created to organise machines into domains and map host names into IP addresses. The address domains are separated from one another by a full stop

DOMAIN:a part of an Internet address (URL) which can be used  for group classification, defined in the Domain Name System (DNS).  E.g..  .com (company),  .ac (academic)

ENCRYPTION: the method of encoding information for security purposes during transmission on the Internet.  The data has to be decoded before it can be read.  Commonly used on the Internet to protect e-mail see ssl and  ROT-13

E-MAIL useful feature for the transfer of simple text electronic messages across a network.  Postings can be to individuals specific groups or general public.  More detailed information including graphic files, program files, spreadsheets can be transferred by the attaching files to an email. Facilities allow the receiver to reply, forward, re-direct, file messages and some systems allow more advanced features indicating when out of office or notification when the messages have been received or when they have been read.  see mimeppppop smtpspamUUencode

FAQ (Frequently Asked Questions) produced for each topic area.  Provides answers for anticipated questions

FINGER a Unix program allows basic information about Internet users or hosts to be retrieved.

FTP (File Transfer Protocol) using FTP program it is possible to copy files from one machine to another via the Internet.  Large amounts of data is easily accessed from on-line databases as well as remotely transferring files to to a web server to set up a web page. A ftp usually ensures that data is transferred error free and for retransmitting any blocks of corrupt data. see protocol

FYI (For Your Information) A series of technical documents on various Internet-related topics, available on many public FTP sites.  See also  RFC

GIF (Graphic Interchange Format) form of compression of graphics files. see also JPEG

GOPHERis a tool for search and retrieve text based information stored on gopher sites throughout the world.  Most modern Browsers (Netscape or Internet Explorer) can handle gopher queries.  On Gopher servers data is held in a hierarchical bases similar to a directory structure which can be "time consuming" to navigate and a search system called VERONICA indexes all items on gopher servers which can be searched in a similar manner to search engines on the Internet.

HOT JAVA is an interpreter required to run JAVA - interprets JAVA programs to run on your specific platform/Operating System.  See JAVAinterpreter

HTMLis the standard language of the web.  It is merely a standard 7 bit ASCII files with formatting codes (tags) included.  The language allows hyper-links to other files or targets within the same file.  E.g.. < A HREF="glossary.htm">General glossary</A>  would make the text "General glossary" on the web page a hyperlinks to another file glossary.htm see languages

HTTP  (Hypertext Transfer Protocol) the protocol that WWW clients and servers use to communicate with each other.see protocols

HYPERTEXT Instead of writing a complex document, uncluttered, simple explanations can be provided and Hyperlinks to other areas allow the individual to widen the information base if extra detail is required.  Often used in Windows help files as well as web pages.  Used extensively throughout this web site to link to other relevant sources.

IMAGE MAP:  a graphic on a web page which allows a different action to be carried out dependant upon which part of the image is clicked upon.  An associated map file is needed to identify which hot spot is responsible for which action.

INTERNET:  a huge world-wide network or more correctly network of networks using TCP/IP protocols to communicate with each other.

IP ADDRESS:  is the unique address for each computer on the Internet.  The IP address appears as a set of four numbers (octets), separated by fullstops.  (the numbers indicate the domain, the network, sub network and the actual host machine).

There are currently not enough addresses to go around with the 16 bit addresses used (this may be remedied when the new 32 bit standard is accepted).  The way around this shortage is for blocks of addresses to be allocated to each ISP who allocates the addresses dynamically to customers for the duration of their logged on session.  Alternatively companies with Intranet may use a proxy server to separate internal/external traffic.  The internal IP addresses can therefore be allocated even if they are used by someone else on the Internet.

ISDN (Integrated Services Digital Network) allows faster speed of transmission and allows integration of both voice and non voice services.

ISP(Internet Service Provider) Most home users will access the internet via an ISP.

JAVA  is a compiled, object-oriented programming language developed by Sun Microsystems, it originated from a program called OAK.  It is a good code to be used on smart cards.  It has been modified to handle internet URLs and is ideal for use in web pages making CGI script largely obsolete. This language was designed for across platform use.  Rather than distribute executable programs as with normal CGI, Java writers distribute instructions that are  interpreted at runtime by a run-time interpreter program within each user's browser. The code is not fully compiled as that would make it platform dependant, it is compiled into a neutral code (byte code) which is finally interpreted at runtime by the users browser.  This makes the code truly cross platform.  Although a fully compiled C program is initially slower once compiled it would then run faster on the browser that downloaded the program.  This would be fine if the programme were to be repeatedly used, but this is not usually the case.  Java programs are often downloaded and used once only.  Once compiled C programs cannot be used universally across other browsers.

Java source code (produced) ---> compiled (into bytecode) -->interpreted by browser (using a runtime interpreter)

Java draws heavily upon C and has much in common with C++.  It is very difficult to distinguish from small pieces of code whether it has been written in C or Java as the syntax is so similar. Considerd better tha C++ as it is not platform/operating system dependant and a lot of the complex C/C++ procedures have been simplified.  (Java binary downloads can take a long time but can be overcome by using JAVA's pre-emptive multi-threading capability).  Netscape, Internet Explorer and some other browsers support Java.

Java is often used to develop applets that are delivered on the WWW and executed in client web browsers.  However it is a 'full blown' language which can also be used to develop complete, platform-independant GUI applications using the Java runtime interpreter.

see  languagesAppletsByte code  JavascriptSue's page  Java Virtual Machine  JDKJava factfile No.1

JAVA DEVELOPMENT KIT (JDK) A suite of programmes available (free) from Sun to help programme Java code. see  RAD

JAVASCRIPTis an object-oriented interpreted language embedded into other code (ASCII text). It is intended for client-side operation, not server-side, whereas Java can be used in either environment.  JavaScript code is interpreted when required and embedded within other code such as HTML.  Both JaveScript and VBScript are interpreted and compiled while the browser downloads from a Web Server.  The code is identified as Javascript by tags within the standard HTML text. The latest version of JavaScript allows script code to be developed and maintained in a seperate file with a .js extension.  This file acts in a similar fashion to an applet in Java, it can be referred to within the script from whichever page wishes to run it. Repetition of the whole of the JavaScript code on each web page is cut out as each page refers to the single file, it also makes maintainance and modifications much simpler to carry out.

<HTML>
<HEAD>
<script language ="JavaScript">
<!-- hide script from old browsers // tells browsers which do not support Java to ignore the code
       JavaScript code...............................  // code for browsers with run-time interpreters
        .............................................etc.
-->
</script>
</HEAD>
</HTML>

Netscape developed the scripting language under the name LiveScript and incorporated it into their browser. Netscape and Sun joined efforts to establish it as a main scripting language.  Because of the close similarity with Java's syntax it was decided to rename it as JavaScript in 1995, so it is a relatively new language and still developing.

JavaScript was designed to help the nonprogrammer in creating interactive applications for the Web and to facilitate the integration of Java and HTML.  Although having different roles both are based upon the same principles.  They are both programming languages with similar commands and syntax, they are both object-oriented, and they are both open and across platform.

JavaScript is an interpreted langauage, meaning that it can run directly within a browser and requires no compilation, whereas Java requires compilation prior to execution.  In addition, JavaScript supports a smaller set of data types and JavaScript methods do not require special declarations as does Java.

JavaScript contains many built-in objects that require minimal effort to create.  Javacript has no classes or class inheritance like Java, instead relying upon the built-in set of objects to be extended to suit the needs of the programmer.  Because JavaScript is interpreted and not compiled, all objects are checked at run-time, whereas Java requires that all references exist at compile time.  Also, a variable's datatype need not be declared as it has to be in Java..

JavaScript was created as an easy-to-use, open, cross platform scripting language that could link together objects and resources from both HTML and Java.  While Java applets are primarily developed by programmers, JavaScript was intended to be used by HTML page authors to dynamically control the interaction and behaviour of their pages.  One benefit of JavaScript is the capability to reduce network traffic by keeping simple tasks local.

JavaScript code is contained within the HTML coding and can be copied by anyone who visits a web site.  However, Java application code is compiled into byte-code on the server.  This byte-code is the actual code received and run by the platform browser,  This compiled code does not contain the original source code.  As the user cannot see the source code, as opposed to JavaScript code which is embedded within the HTML code, Java source code is protected; allowing authors to maintain copyright.

One promising aspect of learning JavaScript is that the novice to programming will be able to start to appreciate how object-oriented languages work.  Then having grasped the basic concepts wil be well on the way to mastering Java.

JavaScript, unlike Java, requires very few resources to use the program.  Because it is an interpreted languge anyone can develop the code using a text editor.  It does not require the Rapid Application Developement (RAD) programs, compilers, linkers, debuggers etc as does Java.

also see  Scripting languageslanguages JavaHot Java Byte code AppletsVbScriptSue's page Java factfile No.1

JAVA VIRTUAL MACHINE (JVM) Java code is not written for any one type of physical computer.  It is written in byte code, for an imaginary computer called the Virtual Machine, which is really another piece of software.  The Virtual Machine is programmed for specific machines, so there is a Windows 95 VM, a Sun VM and a VM built into some Web Browsers such as Netscape etc..  The Virtual Machine then finally interprets the byte code for the particular station using a runtime interpreter.  This is the reason that the same code can run on a Sun workstation or Windows NT.  The author of a programme does not have to worry what type of station will run it.  see Byte code  JavaJavascriptHot java

JPEG: a format for compressed graphics files commonly used in WWW documents.  see also  GIF

LANGUAGESon the Internet a range of new languages have been developed along with existing languages to provide a range of user interaction.  Many languages such as HTML have program generators written in the form of Composer (Netscape) or FrontPage (Microsoft) which enable non programmers to design their own web page with a user friendly word processor (WYSIWYG) type of programme.  The program code is automatically generated for them.

Cgi-scripts allow small self contained programmes (using standard objects e.g.. radio buttons, tick boxes etc.)  to be inserted into a web page.  These can be in the form of counters, guest books, query boxes, e-mail links etc.  These scripts are often retained in secure server-side directories by the host, but can be called by the client on request (security feature to protect host sites from viruses, or malicious scripts developed by users)

Other languages such as Java enable the designer to develop active pages (small self contained programmes "Applets", contained on the server-side, can be pushed onto the user's computer by the server.  Or standard server-side cgi-scripts can be requested by the client. see cgi-script, javascript, appletsVBScript, VBA, Java, ActiveX, PERL,Unix Shell Script, Script, C, C++,

MIME (Multipurpose Internet Mail Extension) Allows the attachment of files to an email (e.g. word processed documents, graphics, spreadsheet, sound and video files etc.). The attached files need to be encoded and then decoded at the receiving end.  It is therefore necessary to ensure that the receiver has the correct decoding facility.

MOZILLA is the name for early Netscape products and for the Netscape specific extensions to the HTML language.

MUDS & MOOS  text based multi-user interactive games, accessed using specialized software or Telnet

OLE (Object Linking and Embbeding) Visual Basic uses this principle.

PERL acronym for Practical Extraction and Report Language.  A free program which overcomes some of the deficiencies in C and UNIX shell programming.  PERL programmes use a .pl extension.  It is an interpreted language, rather like a DOS batch file.  When you execute a Perl program, the Perl instructions are interpreted and compiled into machine instructions in real time.  Other languages such as C are compiled ahead of time  into executable .exe files which are not normally referred to as script.  Although executable files are usually faster, they are more complex and harder to modify.Perl is a favourite for writing CGI scripts.  see languages and  Sue's page

PLUG-INS: are programs that can be easily installed and used with a Web browser.

POP3 (Post Office Protocol-version 3)  used by e-mail programs to retrieve messages from the e-mail server.  see also SMTPe-mail  and  protocols

PORT NUMBER: Computers that run TCP/IP protocols can use different ports to run different services

PPP (Point-to-Point-Protocol)a protocol for connection to the internet by accessing an ISP using a modem and telephone line.  Has improvements over SLIP

• Handle error detection
• supports multiple protocols
• IP addresses can be negotiated at connection time
• allows authentication

PROTOCOLS  Standards governing the transfer of information between computers.see http, PPP, FTP, POP, TCP/IP,SLIPSMTP

RAD (Rapid application Development) GUI to assist programmers in writing computer code. Netscape Composer assists the development of HTML when designing Web pages.    Typical examplesof Java Developer programmes are Borland J Builder Professional, Microsoft Visual InterDev,  Symantic Visual Cafe. see JDK

RADIO BUTTONallows the user to select an option, differs from a check box in that only one selection in a group may be selected. (acts as an "OR" feature)

REMOTE LOGINusing Telnet, Rlogin or other programs, users can log into another computer from anywhere on the Internet.  If the user does not have an account they can often login in as an anonymous guest.

REVERSE LOOKUP  looks up the calling users Domain Name when all that is known is the IP address assigned by SLIP or PPP.  Some security sites will refuse access if they cannot identify the caller's domain name.

RFC (Request For Comments) is a proposal or report placed on the Internet to generate comment.  Often used when establishing technical standards.

ROT-13 is a form of encryption applied to some Usenet messages.  It rotates the alphabet 13 places forwards or backwards.

SCRIPTING LANGUAGE  software programmes that do not need to be compiled.  The code is run by another program as read within the command instructions.Mainly used in HTML coded web pages.  See JavaScriptVbScript

SEARCH ENGINE: to access the huge bank of information on a certain subject (which can be dispersed across the World Wide Web) various search engines have been designed to locate information sources.  Different search engines use different search techniques.  Some engines using one search style can be more successful at locating specific information than others.  Databases of Web page details  are maintained, and by entering keywords or phrases, suitable sites are identified and summaries of database entries matching the search requirements are presented to the user.  When a company or individual wish to publicise their web site they can register their page to be placed on a number of these search engine databases. Examples of search engines:- Yahoo, Lycos, Alta Vista and Magellan.   see GopherArchieVeronicaWAIS

SERVER: ( a computer which provides a specific service on a network) on the Internet, servers control:- file access  on  web sites, communications (email) and FTP sites.  They communicate with clients when requests are made.  Normally the clients work on their own, only going back to the server when needing to, this is a form of a very large distributed network. The services provided are accessed by clients

SERVER PUSH a technique for a Web server to initiate the transmission of data to a client.   Often used for animation or sound.  see also client pull

SERVER-SIDE programs, accessible by a client that are running on a web server are said to be "running on the server-side" as oppoosed to running on the clients own machine.  see client-side

SLIP(Serial Line Internet Protocol) a protocol for connection to the internet via a modem and telephone line, but it has weaknesses and PPP is often used instead.

• SLIP does not provide error detection or correction and transmits raw IP packets.
• It only supports IP and will not support the other network systems such as Novell  LANs.
• SLIP must know the IP address in advance.  This causes problems when connecting via an ISP who only has a block of IP addresses.  It is usual for such ISPs to allocate the user a temporary IP address for the period on line, this could change each logon.
• SLIP doesn't provide any form of authentication and although this is not a problem on leased router-to-router lines it is a problem on dial-up connections.
• As it is not  an approved standard there are many versions of it.

SMTP (Simple Mail Transfer Protocol) is the most common protocol for sending e-mail messages over the Internet  see also  POP3 e-mail and  protocols

SPAM is unwanted e-mail.

SSL (Secure Socket Layer) is an encryption system built into servers or browsers that uses 'certificates of identity' to authenticate sites and users.  These certificates are 'digitally signed' and issued by a trusted third party such as VeriSign.

TAGS: HTML is basic text with tags inserted to inform a browser how to format the text or interpret the instructions. A typical example of a tag is <B> text </B>.  "text" between the on/off tags would appear in bold.  A wide range of tags are available. E.g.. <HTML> </HTML> tags  inform the browser to treat the data between the tags as HTML data.  <SCRIPT LANGUAGE = "JAVASCRIPT"> would treat the text as javascript program instructions.  <HREF..............................>  in it's various forms would produce a hyperlink to some other target in the same document, another file or even another website.

TCL (Tool Command Language) called tickle

TCP/IP(Transmission Control Protocol/Internet Protocol) governs the communications between all computers on the Internet.  It instructs on how packets of data are transmitted across the networks with built in error detection.

IP specifies and determines where packets are routed, based upon the destination address.

TCP/IP must be running and in DOS/Windows applications is handled by WINSOCK but is part of Unix operating system

see  protocols

TELNET is an Internet protocol that allows the user to log into another computer system via the Net.  see   protocols

Unix Shell Script Unix has been the base language used in the development of the Internet.  There are a number of shells but  the standard shell is the Bourne Shell, named after it's creator.  A popular derivative is the Bourne Again Shell, or bash . Another popular flavour is the C shell, csh, which has a syntax similar to the compiled programming language C.see languages and  Sue's page

Unix shell programming language is similar to batch programming where a text file is created of commands in the order that they are to be implemented.

URLUniform Resource Locator is an addressing scheme that let browsers know where to go, how to get there and what to do when they get there.   The address is made up of a number of octets.  The first may contain the protocol being used, a file address or the type of session to be used (e.g.: http, ftp,///C|; telnet, news or WAIS )

A typical fictitious URL could be http://www.locol.ac.uk/~scahills/index.html which would relate to:
http-protocol, www-(world wide web), locol-(Loughborough College, ac-academic domain), uk-(United Kingdom), ~scahills-user, index.html-web site home page

UUENCODE is a method of encoding binary data so that it can be sent as an ASCII file across networks by e-mail.  A UUdecoder is required to convert the file back into an executable binary file again. see  e-mail

VBA (Visual Basic for Applications) MicroSoft made visual basic the backbone for its Office application suite. VBA has become the standard scripting language for Windows.It includes an integrated database engine and data controls for linking to other database programs (very slow on low spec machines)see languages and  Sue's page

VBScript (Visual Basic Script) is Microsoft's answer of an Internet language to be used within it's browser Internet Explorer.  The programs can make use of a large number of DLLs (Libraries) already on most peoples machines or readily available from other sources. see  Scripting language   translation,JavaScriptlanguages and  Sue's page

VERONICA is a system, very similar to Archie, that lets you search gopher sites for menu items. also
see search engines
 

WAIS (Wide Area Information Server) is a networked information retreival service.  Searches are made using keywords.  Servers search a full text index and return lists of documents (abstract) containing the keywords. The user can then request a copy of any documents found.  Multi media data (vidoe, sound etc) can be found as well as ASCII text.  Documents are put into order with those registering the most hits at the top.  WAIS databases can be accessed using WAIS client programs, Gopher,Telnet and Web browsers. See  search engines

WINSOCK (Windows Sockets API) a software toolkit that provides standards for Windows to work with TCP/IPservices
 

XOFF a special character that is used to control the flow of data between DCE and a DTE.  When a device receives an XOFF character from the other, it stops transmitting until it receives an XON

XON a special character used in conjunction with XOFF to control data flowing between DCE and DTE