Internet chp-5

• Internet


  INTERconnected NETwork
• World Wide Web (WWW)


  Part of the internet that users can access using web browser software
• Differences between the internet and the World Wide Web (WWW)

  • Users can send and receive emails
  • Allows online chatting (via text, audio and video)
  • Makes use of transmission protocols (TCP) and internet protocols (IP)
  • It is a worldwide collection of interconnected networks and devices
  • It has various uses in entertainment, education, research, navigation, advertising, and even banking
• Differences between the internet and the World Wide Web (WWW)

  • It is a collection of multimedia web pages and other information on websites
  • https(s) protocols are written using hypertext mark-up language (HTML)
  • Uniform resource locator (URLs) are used to specify the location of Web pages
  • Web resources are accessed by web browsers. Uses the internet to access information from web servers
  • It is used for accessing resources throughout the world
• Differences between the internet and the World Wide Web (WWW)

  • It is a large global network formed by millions of smaller networks
  • It is an entire infrastructure
  • It is hardware-oriented
  • It is independent of the world wide web
  • It functions using an IP address
• Differences between the internet and the World Wide Web (WWW)

  • It is an information system where data is stored for people to access
  • It is a particular service inside an infrastructure
  • It is software oriented
  • It is dependent on the internet
  • It functions using HTTP
• Uniform Resource Locator (URL)


  A text-based address for a web page; it can contain the protocol, the domain name and the web page/file name
• Uniform Resource Locator (URL)

  The website address is: domain host (www), domain name (website name), domain type (.com, .org, .net, .gov, for example), and sometimes country code (.uk, .de, .cy, for example)
• Uniform Resource Locator (URL)

  What we recognize as a website address, made up of the access protocol (http or https) and a domain name, for example amazon.com
• Uniform Resource Locator (URL)

  1. Typed into a browser address bar

  2. Translated by a domain name server into the 32 bit binary IP address

  3. Far easier for a user to remember than a 32 bit binary number
• Hypertext transfer protocol (http)


  A set of rules that must be obeyed when transferring files across the internet
• Hypertext transfer protocol (https)


  A more secure way of sending and receiving data across a network, the 's' stands for secure
• HTML


  Used to create web documents including text, images, formatting, and hyperlinks to other documents
• HTML document


  1. Consists of text and 'markup' tags which are used to define the structure, appearance, and function of the information

  2. Consists of two elements, the header and the body

  3. Header declares the document type(HTML), the page title, and any special instructions for the page, such as plugins to be used or scripts to be run. Additionally, the header include any CSS

  4. The body contains the content to be displayed, hyperlinks to other pages and if a CSS is not used, any formatting instructions for the content
• Markup in HTML

  Take the form of tags. Content that requires formatting in some way is tagged. Tags enclose the content, with an opening tag<> at the beginning of the content and a closing tag</> at the end
• Browser

  A program that allows the computer to visit, retrieve and display the information that a webpage contains
• Accessing a website

  1. The user inputs the website's web address (URL) into the browser

  2. The URL is translated into the unique internet address of the web server that hosts the website

  3. The browser accesses the website based on the URL and downloads the content

  4. The browser allows the user to navigate to different webpages on the website and to other websites via hyperlinks
• Browsers

  • They interpret (translate) the HTML from websites and show the result of the translation; for example, videos, images/text and audio on the user device
• Features of most browsers

  • They have a home page
  • They can store a user's favorite websites/web pages (referred to as bookmarks)
  • They keep a history of websites visited by the user (user history)
  • They have the ability to allow the user to navigate forwards and backwards through websites/web pages already opened
  • Many web pages can be open at the same time by using multiple tabs
  • They make use of cookies
  • They make use of hyperlinks that allow navigation between websites and web pages; links can be opened in one of two ways: either open in a new tab by using <ctrl> + <click> or open in the same tab
  • Data is stored as a cache
  • They make use of JavaScript
  • They use an address bar
• Purpose of a web browser

  To render hypertext markup language (HTML) and display web pages
• Functions of a web browser

  • Storing bookmarks and favourites
  • Recording user history
  • Allowing use of multiple tabs
  • Storing cookies
  • Providing navigation tools
  • Providing an address bar
• Markup Language

  • 
    
• Cascading Style Sheets (CSS)

  A text file with an .css extension that contains a series of commands or rules to tell the HTML how to display
• CSS


  • Once created, the style sheet can be applied to any HTML document
  • By separating the style from the content, the style can easily be changed without having to also change the content and vice versa
  • CSS have huge benefits for website designers, as all the pages of a site can be quickly and uniformly updated simply by changing the mark-up instructions in the style sheet
  • Each HTML page provides the content and structure and the CSS specifies the presentation
• Domain Name Server (DNS)

  A system for finding IP addresses for a domain name given in a URL
• DNS process

  1. The user opens their browser and types in the URL (www.hoddereducation.co.uk) and the browser asks the DNS server (1) for the IP address of the website

  2. The DNS server (2) finds the URL and can map it to 107.162.140.19; this IP address is sent back to the DNS server (1) which now puts this IP address and associated URL into its cache/database

  3. This IP address is then sent back to the user's computer

  4. The computer now sets up a communication with the website server and the required pages are downloaded. HTML files are sent from the website server to the computer. The browser interprets the HTML, which is used to structure content, and then displays the information on the user's computer
• Cookie

  A small text file sent from a website to a user's browser; it is used to remember user preferences each time they visit the website
• Purposes of cookies


  • Helping keep track of whether or not a user has logged in to secure websites
  • Storing dynamic data such as facilities would not be available
  • Tracking a user's interest surfing activities and then tailor online adverts to match the user's interests
  • Storing sensitive information such as passwords and credit card details
• Types of cookies


  • Session cookie - a cookie that is stored temporarily on a computer; it is deleted when the browser is closed or the website session ends
  • Persistent (or permanent) cookie - a cookie that is stored on the user's hard drive and only deleted when the expiry date is reached or the cookie is deleted by the user
• Uses of (Persistent) Cookies

  • Allowing the website to remember users' passwords, email addresses and invoice details, so they won't have to insert all of this information every time they visit or every time they purchase something from that website
  • Serving as a memory, enabling the website to recognise users every time they visit it
  • Saving users' items in a virtual shopping basket/cart
  • Tracking internet habits and users' website histories or favourites/bookmarks
  • Targeting users with advertising that matches their previous buying or surfing habits
  • Storing users' preferences (for example, recognise customised web pages) are used in online financial transactions
  • Allowing progress in online games and quizzes to be stored
  • Allowing social networking sites to recognise certain preferences and browsing histories
  • Allowing different languages to be used on the web pages automatically as soon as users log on
• Uses of Cookies


  • Saving personal details
  • Tracking user preferences
  • Holding items in an online shopping cart
  • Storing login details
• Internet Service Provider (ISP)


  A company that provides us with access to the internet, normally for a fee
• Types of internet connections

  • Dial-up connection - an older style of connection to the internet, uses only telephone lines to connect to the internet, cheaper but slower
  • Broadband connections - an alternative way to access the internet, sometimes uses different cabling to telephones wires, such as fiber-optic cables, allowing a much quicker speed to access to the internet than dial-up connections
• Terms of service for ISPs

  • Details such as the amount of data a customer can download
  • Covering any legal issues such as using the service for hacking
  • Allowing a customer to personalize access to the internet, such as setting a filter that will prevent access to any underage websites
• Web server


  A computer that hosts a website
• Accessing a website

  1. Retrieving information from a web server is known as downloading

  2. Sending information to a website is known as uploading

  3. A computer that accesses information from a web server is called a client

  4. Accessing a website is known as a request
• Web servers


  • They are designed to handle many requests from many clients at the same time
  • Requested information is downloaded from a web server in packets, a unit of data that can be sent across a network
  • The more bandwidth a web server has access to, the more requests it can handle at the same time
• Web servers are also used to manage things such as data storage, online multiplayer gaming and email
• Terms of service


  The rules that a customer must follow when using the service from the ISP
• Terms of service will normally show details such as the amount of data a customer can download