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Introduction to Web Development 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 cross-referenced documents that existed on the CERN computer network Hypertext linking allows you to quickly open other Web pages

Introduction to Web Development (continued) A document on the Web is called a Web page 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

Introduction to Web Development (continued) Web pages are displayed using a program called a Web browser A Web server is a computer that delivers Web pages The most popular Web server software is Apache HTTP Server (Apache) The second most popular Web server is Microsoft Internet Information Services (IIS) for Windows

Goal To provide information to the user:- Files holding information must be created These file must be store at a central location on computer When required the user should be allowed to access these file using there desktop computers A network link must be establish between the desktop computer and the computer serving information at a central location.

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

Web Communication Protocols (continued) 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

Web Communication Protocols (continued) 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 (may be shared). 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

Web Communication Protocols (continued) Protocol Domain name Directory Filename

Client/Server Architecture 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 (continued) 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

Client/Server Architecture (continued) 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

Client/Server Architecture (continued)

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)

HTML Documents (continued) 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

Cascading Style Sheets A single piece of CSS formatting information, such as text alignment, is referred to as a style The term cascading refers to the ability for Web pages to use CSS information from more than one source

Cascading Style Sheets (continued) CSS properties: CSS styles are created with two parts separated by a colon The property refers to a specific CSS style The value assigned to it determines the style’s visual characteristics Together, a CSS property and the value assigned to it are referred to as a declaration or style declaration

Cascading Style Sheets (continued) Inline Styles Allow you to add style information to a single element in a document Internal Style Sheets Create styles that apply to the entire document P { color : blue } selector property value External Style Sheets A separate text document containing style declarations that are used by multiple documents on a Web site

JavaScript and Client-Side Scripting JavaScript is: A client-side scripting language that allows Web page authors to develop interactive Web pages and sites Used in most Web browsers including Firefox and Internet Explorer Client-side scripting is a language that runs on a local browser (on the client tier) instead of on a Web server (on the processing tier)

JavaScript and Client-Side Scripting (continued) JavaScript allows you to: Turn static Web pages into applications such as games or calculators Change the contents of a Web page after a browser has rendered it Create visual effects such as animation Control the Web browser window itself

Server-Side Scripting and PHP Server-side scripting refers to a scripting language that is executed from a Web server Hypertext Preprocessor (PHP) is a server-side scripting language that is used to develop interactive Web sites Is easy to learn Includes object-oriented programming capabilities Supports many types of databases (MySQL, Oracle, Sybase, ODBC-compliant)

Server-Side Scripting and PHP (continued) PHP (continued): PHP is an open source programming language Open source refers to software where source code can be freely used and modified Can’t access or manipulate a Web browser like JavaScript Exists and executes solely on a Web server, where it performs various types of processing or accesses databases

Server-Side Scripting and PHP (continued) General rule: Use client-side scripting to handle user interface processing and light processing, such as validation; use server-side scripting for intensive calculations and data storage