5. Internet

• People often use the words the internet and the world wide web interchangeably to mean the same thing, but they are not the same thing
• The internet

  1. Foundations in the 1960s as a way for government researchers to share information

  2. Led to the formation of ARPANET (Advanced Research Project Agency Network) as a way to allow armed forces to communicate over a connected distributed network during the Cold War

  3. ARPANET expanded to connect beyond the military and started to connect third-party contractors and universities in the U.S.

  4. By the mid-1970s, ARPANET had connected to NORSAR (the earthquake monitoring system) in Norway and then to computers in London and eventually other parts of Europe

  5. Initially, the different computer networks had no single standard way to communicate with each other

  6. ARPANET eventually adopted the TCP/IP protocol as a standard way for different kinds of computers to talk to each other on January 1, 1983, which is considered the point where the internet was really born
• The world wide web

  1. Concept developed in 1989 by British scientist Sir Tim Berners-Lee working at CERN

  2. Idea was to have a decentralized repository of information linked together and shareable with anyone who could connect to it via the internet

  3. Berners-Lee built the very first website in 1993 and then CERN opened up the software for the web to the public domain

  4. Berners-Lee was also responsible for creating the very first website browser, initially called World Wide Web and later renamed to Nexus
• Internet


  A worldwide interconnected series of computers and networks
• World wide web

  A collection of websites and web pages accessed using the internet
• Uniform Resource Locator (URL)

  A unique text-based address that relates to a web page
• Accessing web pages


  Typing the URL into a web browser (e.g. Google Chrome, Microsoft Edge, Apple Safari)
• URL structure

  • Protocol (e.g. HTTPS)
  • Host
  • Domain name (website domain)
  • Location within the website
  • Resource (web page or file)
• Fully Qualified Domain Name

  The combination of the host and the domain name
• Protocols are discussed in more detail in a later video
• Protocol


  A set of rules that allows two devices to communicate
• Two people only speak one language each

  They are unable to communicate
• Two people share a common language


  They are able to communicate
• A protocol is a set of rules that allows two devices to communicate
• HTTP (Hypertext Transfer Protocol)


  A way for a client and a server to send and receive requests and deliver HTML web pages. It is the fundamental protocol of the World Wide Web.
• HTTPS (Hypertext Transfer Protocol Secure)


  The same as HTTP, but it adds encryption and authentication. HTTPS should be used whenever a website deals with sensitive information such as passwords or bank account details.
• The first part of a URL specifies the protocol
• Web browser

  Renders hypertext markup language (HTML) and displays the web page
• Web page

  • HTML code on the left
  • How the user sees the web page on the right
• Web browsers

  • Store bookmarks and favorites
  • Record user history
  • Allow multiple tabs
  • Store cookies
  • Provide simple navigation tools
  • Provide an address bar
• Bookmarks/Favorites

  Allows users to save and organize web pages for easy access
• Browser history

  Allows users to easily navigate back to previously visited sites
• Multiple tabs


  Allows users to have different web pages and sites open at the same time
• Cookies


  Small text files with ID tags stored on the user's computer to track movement within a website and customize the user experience
• Navigation tools


  • Go back to last page visited
  • Go forward to a page just navigated back from
  • Return to a customizable home page
  • Refresh the current webpage
• Address bar

  Contains the URL of the current web page
• Internet


  The largest and most well-known wide area network, a collection of interconnected networks spanning the world
• The internet is not the same as the World Wide Web, which is just a service provided on the internet</b>
• Web servers

  • Carry out functions like hosting websites and dealing with client requests
• Rendering a web page

  1. Web page stored as HTML, CSS, JavaScript and other multimedia files is sent to a browser

  2. Browser uses various rules to render the web page correctly
• Locating a web page


  1. Client requests a URL via a web browser

  2. Browser sends the domain name to a domain name server

  3. Domain name server maps the domain name to an IP address and returns it to the browser

  4. Browser sends a GET request for the web page to the web server using the IP address

  5. Requested web page is returned to the client's web browser
• Domain Name Service (DNS)


  A series of separate domain name servers that ultimately return an IP address to a specific server hosting a web page from a human-friendly URL
• How DNS works

  1. Browser receives URL (e.g. www.google.com)

  2. Browser sends query to a root name server

  3. Root name server responds with address of top-level domain (TLD) name server (e.g. .com)

  4. Browser sends query to TLD name server

  5. TLD name server responds with IP address of domain's name server

  6. Browser sends query to domain's name server

  7. Domain's name server returns IP address of web server to browser
• Cookie


  A small text file with id tags that's stored on your computer, created when you use your browser to visit a website
• Cookies

  • Used to keep track of your movements within the website
  • Can help by resuming where you left off when you revisit the site
  • Remembering your registered login details
  • Remembering theme selections preferences
  • Furthering and customizing your experience
• By law, any website operator must tell users the cookies are there, explain what they're doing and obtain the user's consent to store cookies on their device
• Types of cookies

  • Session cookies
  • Persistent cookies
• Session cookies


  Created and replaced every time you visit a website
• Persistent cookies


  Created and saved on the first visit to a website and retained until they expire
• Modern browsers will allow you to view the content of all cookies currently stored on your device and clear them if you wish