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Lecture1 Website Development Forth Stage Assistant Lecturer: Ahmed Habeeb Al Azawei The Internet: The history of the Internet began in 1969 as a scientific and military research program called ARPANET (Advanced Research Projects Agency Network). This program composed four computers, three in California and one in Utah, the experiment was to develop the first system of transfer of information in the event of network outages every day, and perhaps time in times of global thermonuclear war (this was the Cold War, after all). Packet-switching a system enables small packets of data to be sent independently of each other on the destination computer, enables the reliable transmission of data, and is the foundation of the Internet today. The Internet is a worldwide collection of interconnected computer networks that enables businesses, organizations, governments, and individuals to communicate in a variety of ways. One of the most popular ways users communicate on the Internet is by publishing and interacting with Web pages. You can also use the Internet to send and receive e-mail, chat with other users, and transfer files between computers. The computers and computer networks exchange information using TCP/IP (Transmission Control Protocol/Internet Protocol) to communicate with each other. In 2005, more than one billion people worldwide connect to the Internet of 11.5 billion web pages every day. In 2007, the number of Internet users around the globe topped 1.2 billion. TCP/IP When two or more computers communicate, they must have a common way in which to communicate. To do these computers use protocols. A protocol is an agreement by which two or more computers can communicate. Transfer Control Protocol/Internet Protocol (TCP/IP) is the underlying protocol for the Internet. 1) Transfer Control Protocol (TCP) breaks data into small pieces. These “pieces” are called packets. 1 2) Each packet is inserted into different Internet Protocol (IP) “envelopes.” Each contains the address of the intended recipient and has the exact same header as all other envelopes. IP Address Since computers process numbers more efficiently and quickly than characters, each machine directly connected to the Internet is given an IP Address. An IP address is a 32bit address comprised of four 8-bit numbers (28) separated by periods. Each of the four numbers has a value between 0 and 255, Examples of an IP http://134.68.140.1/ The World Wide Web The World Wide Web is a giant collection of documents, or pages, stored on computers around the globe. Commonly called the Web, this collection of pages represents a wealth of text, images, audio, and video available to anyone with a computer and an Internet connection. Web pages are stored on servers, which Internet-connected computers are running software that allows them to serve up information to other computers. When you place a text file, image, or other document in a special Web directory on a server, that information is available for other Web users to view. The Web uses the HTTP (Hypertext Transfer Protocol) to transfer documents formatted in HTML (Hypertext Mark-up Language). These are viewed by using software for web browsers such as Netscape and Internet Explorer. URLs and Links Every page on the Web has a unique address called a URL, which is short for Uniform Resource Locator. A URL looks like this: http://www.example.com/index.html, the URL of College of Science is http://sc.uobabylon.edu.iq. 2 Top Level Domain Names .edu Educational Institution .gov Governmental Agency .mil Military Entity .com Commercial Entity .net Internet Service Provider .org Non-Profit Organization If you know a page’s URL, you can type it into a Web browser to view that page over the Internet. You can also view pages by way of hyperlinks, or simply links, which are clickable words or images on Web pages. Every link on a Web page is associated with a URL that leads to another page on the Internet. Users can jump from one Web page to another by clicking links. IP vs. URL While numeric IP addresses work very well for computers, most humans find it difficult to remember long patterns of numbers. Instead, humans identify computers using Uniform Resource Locators (URLs), “Web Addresses”. Browsers A Web browser is software that allows you to view and interact with Web pages. When you type a URL or click a link in a Web browser, the browser retrieves the appropriate page from a server on the Internet and displays that page. Microsoft Internet Explorer, Mozilla, Firefox and Apple Safari are the three most popular browsers in use today. Each program has evolved through a number of versions, with newer versions supporting more recent Web features. As you build your pages using HTML code, remember that different browsers may display your pages slightly differently depending on the version. A Web browser is software that can retrieve HTML documents from the Web, parse the HTML instructions, and display the resulting Web pages. You can also use a browser to 3 display HTML documents you save locally on your computer. When coding your HTML, you can use a Web browser to test your work. The Usability Concepts: The Usability is the scope to which a system supports its users in finishing their demands efficiently, effectively, and satisfactorily. The main concepts in Usability are: Efficiency is a gauge of the length of time, and the amount of resources, we use in finishing a task. A usable system enables users to complete a task with the minimum of fuss, without having to learn new techniques unnecessarily, and without having to expend more effort than users need. Effectiveness is a gauge of how well users complete tasks. A usable system enables users to complete their tasks to high standard. Satisfaction is a gauge of the scope to which users are pleased with their development in completing a task. A usable system asks for the right amount of information or input, provides useful help when required, and saves users effort. Also many researchers maintained to a common set of ‘heuristics’ to a usability of system are: Navigation The application must have a clear indication of current location, and are there clears navigation elements offering the opportunity to go to other pages of the system. Help & Support The application must given clear advices in case of need and the workflow of the system supports the users to fulfill their demands. Error handling The errors must avoid as much as possible. When errors occur, the system gives clear messages. Consistency The system must have good consistency between its parts, and this consistency in the standard. Control The users need to have control of the application. Visual clarity If the system is attractive, it will provide visual satisfaction to the users. Language The language use in the system must be appropriate to the language of the users. 4