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Web Application Development BY SULTAN MEHMOOD

Introduction  In 1990 and 1991,Tim Berners-Lee created the World

Wide Web at the European Laboratory for Particle Physics (CERN) in Geneva, Switzerland  The original purpose of the World Wide Web (WWW) was to provide easy access to crossreferenced documents that existed on the CERN computer network  A document on the Web is called a Web page

Cont..  A Web page is identified by a unique address called 

  

the Uniform Resource Locator (URL) A URL is also commonly referred to as a Web address A URL is a type of Uniform Resource Identifier (URI) A Web site refers to the location on the Internet of the Web pages and related files Web pages are displayed using a program called a Web browser

Cont.. ď‚— A Web server is a computer that delivers Web pages ď‚— The most popular Web servers are Apache and IIS

HTML Documents  Web pages are created using Hypertext Markup

Language (HTML)  Web pages are commonly referred to as HTML pages or documents  A markup language is a set of characters or symbols that define a document’s logical structure  HTML is based on an older language called Standard Generalized Markup Language (SGML)

 Like SGML, HTML was originally designed as a

way of defining the elements in a document independent of how they would appear  HTML has evolved into a language that defines how elements should appear in a Web browser  Understanding HTML is critical in learning how to write a web application along with the server programming

Web Communication Protocols  A Web page is identified by a unique address called

the URL  Each URL consists of two basic parts: 

A protocol (usually HTTP) and Either the domain name for a Web server or a Web server’s Internet Protocol address

 Hypertext Transfer Protocol (HTTP) manages the

hypertext links that are used to navigate the Web

Cont..  A host refers to a computer system that is being

accessed by a remote computer  A domain name is a unique address used for identifying a computer such as a Web server on the Internet  The domain identifier identifies the type of institution or organization (.biz, .com, .edu, .org)  An Internet Protocol, or IP address, is another way to identify computers or devices connected to the Internet

Cont..  An IP address consists of a series of four groups of

numbers separated by periods  Each Internet domain name is associated with a unique IP address  HTTP is a component of Transmission Control Protocol/Internet Protocol (TCP/IP)  Hypertext Transfer Protocol Secure (HTTPS) provides secure Internet connections for transactions that require security and privacy

Cont.. Protocol

Domain name



Understanding Web Development  Web development, or Web programming, refers

to the design of software applications for a Web site  The Webmaster is responsible for: 

The day-to-day maintenance of a Web site Monitoring Web site traffic and ensuring that the Web site’s hardware and software are running properly Knowledge of Web page design, authoring, and development

Cont..  Server (“back end”):  A database from which a client requests information  Fulfills a request for information by managing the request or serving the requested information to the client  Responsible for data storage and management  A system consisting of a client and a server is known

as a two-tier system

Client/Server Architecture  Client (“front end”):  Presents an interface to the user  Gathers information from the user, submits it to a server, then receives, formats, and presents the results returned from the server

Cont..  A three-tier, or multi-tier, client/server system

consists of three distinct pieces:  

Client tier, or user interface tier, is the Web browser Processing tier, or middle tier, handles the interaction between the Web browser client and the data storage tier Performs necessary processing or calculations based on the request from the client tier  Handles the return of any information to the client tier 



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