Download Lecture1 Website Development Forth Stage Assistant Lecturer

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