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The Internet and the World Wide Web (WWW) | O Level Computer Science 2210 & IGCSE Computer Science 0478 | Detailed Free Notes To Score An A Star (A*)

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  • Internet and the World Wide Web
    • Internet is an infrastructure
      • Different components have made it into one huge network
    • Such network type is called Wide Area Network or WAN
    • Large geographic span
    • World Wide Web is a collection of websites and web pages that is accessible through the internet
  • Requesting and Retrieving Web Pages
    • URL or uniform resource locator is the fundamental component of the world wide web
    • There is a text based address called the address bar.
    • We type it into the web browser
    • Three main components
      • Protocol
        • Set of rules for transmitting data
        • From example Http or https
      • Domain Name
        • Unique name for the web server
        • google.com
      • Web Page
        • The actual file that needs to be accessed
        • /education.html etc.
    • Process
      • Open the web browser and enter the URL into the address bar
      • This URL is then sent to the domain name server (DNS)
        • Special kind of server that stores all the different domain names
        • Equivalent IP address of the domain name etc.
        • Not all stored on a single DNS
      • Database searched, if not there, sent to the next DNS
      • Once the domain name is found
      • Message sent back to the browser telling that the website is found
      • Once the domain name is found, it send the IP address back to the browser
      • IP address is of the server where the website is stored
      • Browser knows where to find the website
      • Web browser sends the request to the web server to ask for the web page from the website
      • The protocol used in this process is called Hypertext transfer protocol (HTTP)
      • A request is send to the web server
      • HTML or Hypertext markup language (HTML)  and CSS (Cascading Style Sheet) is used to create web pages
      • Active part of the script may be used as well such as JavaScript
      • When the server receives the request for the web page, data is sent to the web browser of the website and page.
      • This data is sent in the form of HTML, CSS and script
      • Then, the browser renders the HTML and CSS and runs the active script to display the web page.
    • Other protocols exist as well
      • HTTPS (hypertext transfer protocol secure)
      • Additional layer of security that encrypts the data that is transferred
      • Digital certificates are used
      • First, it needs to be applied for from a certificate authority
      • Certificate authority checks if the website is authentic and original, trustworthy.
      • Then the certificate is issued
      • How the security layer is created
        • Before the web browser sends the request to the web server it sends a request to the web server asking to provide a digital certificate
        • Server sends copy of the certificate to the browser
        • Browser checks if the certificate is authentic
        • If the certificate is authentic, browser will allow communication to continue with the server and any data transferred is encrypted
        • If not authentic, browser will report that the website is not secure
    • Two types of layers used
      • Secure sockets layer (SSL)/ TLS (Transport Layer Security)
      • TLS is newer version of SSL
      • It creates encryption
      • The padlock tells us if the website is secure.
  • Purpose of Web Browser
    • It renders the webpage received from the server
    • Features of browser
      • Address bar where URL is typed
      • User history where all details are saved for previous searches
      • Bookmark to remember the important web pages
      • Tabs so multiple things can be accessed at the same time
      • Window so different windows can be created
      • Navigate between different web pages
      • Cookies manage the process of transmitting them
  • Cookies
    • Small text file that stores data about the user
    • Useful to store that data about what you regularly access on the internet
    • Do not need to enter the data every time.
    • Storing the username and password
    • Storing bank card details
    • Storing products in virtual shopping carts
    • Tailor the online experience of the websites online
    • Cookies are created when you visit a web page
    • Stored in the web browser
    • Two main types of cookies
      • Session cookies
        • Temporary files are created when visiting a web page
        • As soon as browser closed the cookies are deleted
        • The web page will not recognize you if you close the browser and return
        • Online shopping cookies that store your shopping cart
      • Persistent Cookies
        • Permanent files created when visiting a web page
        • Stored on the hard drive b the web browser
        • They are sent back to the server that stores to the web page that provides personal details and preferences
        • Automatically enter details
        • They are either manually deleted or deleted when expired
        • There is an expiration date
        • Once the expiration date has been reached, the browser will delete the cookie from your hard drive
    • Can be seen as breach of privacy
    • Some consider that identity can be stolen
    • We can alter the cookie activity by changing the browser settings
Hunain Zia

Hunain Zia has previously achieved considerable success in the high-school educational stream, gaining a massive 154 Total A Grades and 7 Major Distinctions, a process in which he broke/ set 11 different world records, including the most A grades ever achieved, most subjects ever appeared in, most distinctions, gaining distinctions across two separate boards (Pearson Edexcel and CAIE) within the same year/ ever, and even 19 hours of constant examination. All records stand intact today. Hunain pursued his Honors Accounting Degree from the prestigious Bentley University, and then completed an LLB (in Honors) from University of London. Currently, he manages multiple social and commercial projects, has founded digital streams and works tirelessly in the education sector.

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