A java exception is an object that describes an exceptional condition that has occurred in a piece of code. When an exceptional condition arises, an object representing that exception is created and thrown in the method that causes the error. That method may choose to handle the exception itself or may pass it on. Either way, at some point exception is caught and processed.
Java exception handling is managed by five keywords: try, catch, throw, throws, and finally. The general form of an exceptional handling block is as follows: try
/ /Block of code to moni tor errors.
catch(Except ion1 e)
/ /Block of code to handle Except ion1.
catch(Except ion2 e)
/ /Block of code to handle Except ion2. .
/ /Block of code to be executed before try block ends }
A browser consists of a set of clients, a set of interpreters, and a controller that manages them. Each browser must contain an HTML interpreter to display the document. Other interpreters are optional. The controller forms the central piece of browser. It interprets both mouse click and key board input, and calls other components to perform operations specified by the user.
Q.Dif ferent iate between ht tp and ftp. (5)
FTP and HTTP were developed to make Internet t ransmission bet ter. FTP is used to exchange fi les between computer accounts, to transfer files between an account and a desktop computer (upload) , or to access software archives on the Internet . It ‘s also commonly used to download programs and other fi les to your computer from other servers. It t ransfers fi les in two dif ferent formats ASCII for text f i les and Binary format for binary fi les. This al lows a user to perform basic fi le and directory management operat ions such as delet ing, copying, or renaming. Also, there is something cal led Anonymous FTP used heavi ly today by several universi t ies and private organizat ions. Anonymous FTP is a faci l i ty offered by many machines on the Internet . This permi ts you to log in wi th the user name ‘anonymous’ or the user name ‘ftp’ . When prompted for a password, type your e-mai l address — i t ‘s not necessary, but i t ‘s a courtesy for those si tes that l ike to know who is making use of their faci l i ty. Be courteous. Some si tes requi re a val id e-mai l address, others don’t.
HTTP is used primari ly in today’s society as a set of rules for exchanging fi les (text , graphic images, sound, video, and other mul t imedia f i les) on the World Wide Web. It also provides access to other protocols l ike FTP, SMTP, NNTP, WAIS, Gopher, Telnet , and TN3270. Essent ial concepts that are part of HTTP include (as i ts name impl ies) the idea that fi les can contain references to other f i les whose select ion wi l l el ici t addi t ional transfer requests. Any web server machine contains, in addi t ion to the HTML and other fi les i t can serve, an HTTP daemon, a program that is designed to wai t for HTTP requests and handle them when they ar rive. Your Web browser is an HTTP cl ient , sending requests to server machines. When the browser user enters fi le requests by ei ther “opening” a Web fi le (typing in a Uniform Resource Locator) or cl icking on a hypertext l ink, the browser bui lds an HTTP request and sends i t to the Internet Protocol Address indicated by the URL. The HTTP daemon in the dest inat ion server machine receives the request and, after any necessary processing, the requested fi le is returned.
Internet service provider(ISP)
Internet Service Provider. Any organization that provides access to the Internet. Many ISPs also offer technical assistance to schools looking to become Internet information providers by placing their school’s information online. They also help schools get connected to the Net. In Internet service provider (ISP) is an organization that provides access to the Internet. Internet service providers can be either community-owned and non-profit, or privately owned and for-profit. Access ISPs directly connect clients to the Internet using copper wires, wireless or fiber-optic connections. Hosting ISPs lease server space for smaller businesses and other people (colocation). Transit ISPs provide large amounts of bandwidth for connecting hosting ISPs to access ISPs.
Internet connectivity options from end-user to Tier 3/2 ISPs File Transfer
File Transfer Protocol. An application program that uses TCP/IP protocol to allow you to move files from a distant computer to a local computer using a network like the Internet. File Transfer Protocol (FTP) is a standard Internet protocol for transmitting files between computers on the Internet. Like the Hypertext Transfer Protocol (HTTP), which transfers displayable Web pages and related files, and the Simple Mail Transfer Protocol (SMTP), which transfers e-mail, FTP is an application protocol that uses the Internet’s TCP/IP protocols. FTP is commonly used to transfer Web page files from their creator to the computer that acts as their server for everyone on the Internet. It’s also commonly used to download programs and other files to your computer from other servers. As a user, you can use FTP with a simple command line interface (for example, from the Windows MS-DOS Prompt window) or with a commercial program that offers a graphical user interface. Your Web browser can also make FTP requests to download programs you select from a Web page.
Using FTP, you can also update (delete, rename, move, and copy) files at a server. You need to logon to an FTP server. However, publicly available files are easily accessed using anonymous FTP. Basic FTP support is usually provided as part of a suite of programs that come with TCP/IP. However, any FTP client program with a graphical user interface usually must be downloaded from the company that makes it. File Transfer Protocol (FTP) is a standard network protocol used to transfer files from one host to another host over a TCP-based network, such as the Internet. FTP is built on a client-server architecture and uses separate control and data connections between the client and the server.
FTP users may authenticate themselves using a clear-text sign-in protocol, normally in the form of a username and password, but can connect anonymously if the server is configured to allow it. For secure transmission that hides (encrypts) the username and password, and encrypts the content, FTP is often secured with SSL/TLS (“FTPS”). SSH File Transfer Protocol (“SFTP”) is sometimes also used instead. The first FTP client applications were command-line applications developed before operating systems had graphical user interfaces, and are still shipped with most Windows, Unix, and Linux operating systems. Dozens of FTP clients and automation utilities have since been developed for desktops, servers, mobile devices, and hardware, and FTP has been incorporated into hundreds of productivity applications, such as web page editors Uniform resource locator
Uniform Resource Locater. This is the (rather clumsy) name for the address of any resource on the Internet. You type the URL into your browser, and are taken to that address. In computing, a uniform resource locator (URL) is a specific character string that constitutes a reference to an Internet resource. A URL is technically a type of uniform resource identifier (URI) but in many technical documents and verbal discussions URL is often used as a synonym for URI. Abbreviation of Uniform Resource Locator (URL) it is the global address of documents and other resources on the World Wide Web. The first part of the URL is called a protocol identifier and it indicates what protocol to use, and the second part is called a resource name and it specifies the IP address or the domain name where the resource is located. The protocol identifier and the resource name are separated by a colon and two forward slashes. For example, the two URLs below point to two different files at the domain pcwebopedia.com. The first specifies an executable file that should be fetched using the FTP protocol; the second specifies a Web page that should be fetched using the HTTP protocol: ftp://www.pcwebopedia.com/stuff.exe
A URL is one type of Uniform Resource Identifier (URI); the generic term for all types of names and addresses that refer to objects on the World Wide Web. The term “Web address” is a synonym for a URL that uses the HTTP / HTTPS protocol. The Uniform Resource Locator (URL) was developed by Tim Berners-Lee in 1994 and the Internet Engineering Task Force (IETF) URI working group. The URL format is specified in RFC 1738 Uniform Resource Locators (URL). On the Web (which uses the Hypertext Transfer Protocol, or HTTP), an example of a URL is:
which specifies the use of a HTTP (Web browser) application, a unique computer named www.ietf.org, and the location of a text file or page to be accessed on that computer whose pathname is /rfc/rfc2396.txt. A URL for a particular image on a Web site might look like this:
http://searchnetworking.techtarget.com/WhatIs/images/coaxla.gif A URL for a file meant to be downloaded using the File Transfer Protocol (FTP) would require that the “ftp” protocol be specified like this hypothetical URL: ftp://www.somecompany.com/whitepapers/widgets.ps
A URL is a type of URI (Uniform Resource Identifier, formerly called Universal Resource Identifier.) Web search engine
An online service which can trawl through the contents of the Web (Websites, newsgroups, email addresses) looking for specific phrases or words. The engine asks you for keywords and then provides a list of web sites that contain your chosen words. Clicking on the listed web sites will take you to the relevant web page. A web search engine is designed to search for information on the World Wide Web. The search results are generally presented in a line of results often referred to as search engine results pages (SERPs). The information may be a specialist in web pages, images, information and other types of files. Some search engines also mine data available in databases or open directories. Unlike web directories, which are maintained only by human editors, search engines also maintain real-time information by running an algorithm on a web crawler. Gopher (protocol)
A menu-based system for browsing Internet information.
The Gopher protocol ( /ˈɡoʊfər/) is a TCP/IP application layer protocol designed for distributing, searching, and retrieving documents over the Internet. Strongly oriented towards a menu-document design, the Gopher protocol presented an attractive alternative to the World Wide Web in its early stages, but ultimately failed to achieve popularity. The protocol offers some features not natively supported by the Web and imposes a much stronger hierarchy on information stored on it. Its text menu interface is easy to use, and well-suited to computing environments that rely heavily on remote text-oriented computer terminals, which were still common at the time of its creation in 1991, and the simplicity of its protocol facilitated a wide variety of client implementations.
More recent Gopher revisions and graphical clients added support for multimedia. Gopher was preferred by many network administrators for using fewer network resources than Web services. With its hierarchical structure, Gopher provided a useful platform for the first large-scale electronic library connections. Gopher users remember the system as being “faster and more efficient and so much more organised” than today’s Web services. Although largely supplanted by the Web in the years following, the Gopher protocol is still in use by enthusiasts, and a small population of actively-maintained servers remains. Gopher characteristics
As part of its design goals, Gopher functions and appears much like a mountable read-only global network file system (and software, such as gopherfs, is available that can actually mount a Gopher server as a FUSE resource). At a minimum, whatever a person can do with data files on a CD-ROM, they can do on Gopher. A Gopher system consists of a series of hierarchical hyperlinkable menus. The choice of menu items and titles is controlled by the administrator of the server. Similar to a file on a Web server, a file on a Gopher server can be linked to as a menu item from any other Gopher server. Many servers take advantage of this inter-server linking to provide a directory of other servers that the user can access. Web Home page
The first page a user sees when visiting a World Wide Web site. A home page or index page has various related meanings to do with web sites: It is also usually the first page that the link/site takes the user to. * When the user first opens their web browser, it automatically brings you to this page. * It most often refers to the initial or main web page of a web site, sometimes called the “front page” (by analogy with newspapers). * The web page or local file that automatically loads when a web browser starts or when the browser’s “home” button is pressed; this is also called a “home page”. The user can specify the URL of the page to be loaded, or alternatively choose e.g. to re-load the most recent web page browsed. * A personal web page, for example at a web hosting service or a university web site, that typically is stored in the home directory of the user. * In the 1990s the term was also used to refer to a whole web site, particularly a personal web site (perhaps because simple web sites often consisted of just one web page). A home page can also be used outside the context of web sites, such as to refer to the principal screen of a user interface, which is also referred to as a home screen on mobile devices such as cell phones. URL are one way to track down websites like Google and yahoo which are set as “common Homepages” Internet account
Purchased through an Internet service provider, the account assigns a password and email address to an individual or group. World Wide Web
A revolutionary browsing system that allows point-and-click navigation of the Internet. The Web is a spiderweb-like interconnection of millions of pieces of information located on computers around the world. Web documents use hypertext, which incorporates text and graphical links to other documents and files on Internet-connected computers. Virus
A special type of program which is designed for malicious purposes. It spreads by attaching itself to other programs and then carrying out unwanted and often damaging operations. Telnet
Allows users remote access to computers, most often at libraries, universities, and government agencies.The remote computer thinks you are using its own keyboard. Email
Allows users to send and receive messages to each other over the Internet. Email address
A code representing a unique email user on the Internet. Examples might include – firstname.lastname@example.org, email@example.com