The Internet Salihu Ibrahim Dasuki (PhD) CSC102 INTRODUCTION TO COMPUTER SCIENCE

 Aim ◦ Introduce the World Wide Web  Purpose ◦ To understand how the world wide web, an internet application, is organized and how it operates. CSC102 INTRODUCTION TO COMPUTER SCIENCE

 The world wide web is based on the concept of hypertext.  Hypertext – text documents that contain links called hyperlinks, to other documents.  Text documents were expanded to include images, audio, and video – hypermedia. CSC102 INTRODUCTION TO COMPUTER SCIENCE

 Using a GUI, the user can click on the links to go to other documents, exploring a line of thought.  A web of related information is formed by the hyperlinks  On a computer network, with documents distributed across different computers, it forms a network wide web CSC102 INTRODUCTION TO COMPUTER SCIENCE

 The web of documents on the Internet spans the globe – the World Wide Web  A hypertext or hypermedia on the world wide web is called a web page  A collection of web page is called a web site CSC102 INTRODUCTION TO COMPUTER SCIENCE

 Web browsers (clients) enable users to gain access to web pages on a website  Web servers (servers) provide access to web pages requested by users via web browsers.  Web servers run on computers that contain collections of web pages (forming websites). CSC102 INTRODUCTION TO COMPUTER SCIENCE

 Hypertext documents are transferred between webservers and web browser using the hypertext transfer protocol (HTTP)  Each document is identified using a unique address called a Uniform Resource Locator (URL). CSC102 INTRODUCTION TO COMPUTER SCIENCE

 Hypertext documents contain symbols called tags to say how documents should appear on the screen – what images are present, what links are to occur etc  The system of tags is known as Hypertext Markup Language CSC102 INTRODUCTION TO COMPUTER SCIENCE

 HTML were created to define how text is to be displayed  XML – extensible markup language was created to describe the content of the text – its meaning/semantic  XML forms the backbone of semantic web. CSC102 INTRODUCTION TO COMPUTER SCIENCE

 A note to Gerard, from Michael, containing a heading and a message: CSC102 INTRODUCTION TO COMPUTER SCIENCE

 Compare with HTML: CSC102 INTRODUCTION TO COMPUTER SCIENCE

 If we want interactive web pages, for example to enable a customer to enter flight details and the airline to provide time and cost, then we need:  Client side activities – at the browser for the user to enter information  Server side activities – at the web server for the airline to provide information for that customer CSC102 INTRODUCTION TO COMPUTER SCIENCE

 If we want interactive web pages, for example to enable a customer to enter flight details and the airline to provide time and cost, then we need:  Client side activities – at the browser for the user to enter information  Server side activities – at the web server for the airline to provide information for that customer CSC102 INTRODUCTION TO COMPUTER SCIENCE

 Client side activities are supported by such things as: ◦ JavaScript: allows program to embedded in HTML web page ◦ Applets: programs written in Java language, downloaded separately to the web page, but displayed in the web page ◦ Flash: Multimedia presentations CSC102 INTRODUCTION TO COMPUTER SCIENCE

 Client side activities are supported by such things as: ◦ JavaScript: allows program to embedded in HTML web page ◦ Applets: programs written in Java language, downloaded separately to the web page, but displayed in the web page ◦ Flash: Multimedia presentations CSC102 INTRODUCTION TO COMPUTER SCIENCE

 Server side activities are supported by such things as: ◦ Java server pages: web pages templates stored at the webserver ◦ Active server pages: developed by Microsoft ◦ PhP: (Hypertext Preprocessor) – an open source system for providing server side functionality CSC102 INTRODUCTION TO COMPUTER SCIENCE

 Client side and server side activities, and the systems that support them, provide functionality needed on the web to support business applications such as: ◦ Airline booking system ◦ Hotel booking system ◦ E-Commerce website and so on CSC102 INTRODUCTION TO COMPUTER SCIENCE