IB CS Option C

• Internet


  A very large Global Network that allows users to access the World Wide Web
• World Wide Web


  The actual web pages and websites that are stored on the infrastructure of the internet
• Differences between the Internet and the World Wide Web


  • Internet is devices, World Wide Web is websites
  • Internet can be accessed through all devices, World Wide Web requires a web browser
  • Internet uses protocols like TCP/IP, email, FTP, World Wide Web uses HTTP
• Every website is stored on a server, each server has an IP address
• Accessing a website


  1. Web browser sends a request to the server at the IP address

  2. Server responds with the web page content
• Protocols


  A set of rules and guidelines that govern how data is transmitted, received and processed across a network
• Examples of protocols


  • TCP/IP
  • HTTP
  • FTP
  • SMTP
• URL (Uniform Resource Locator)


  An address that allows you to access a website, composed of protocol, domain name, and web page name
• URI (Uniform Resource Identifier)


  Identifies the location of a resource, a URL is a type of URI
• Translating a URL to an IP address


  1. Web browser sends URL to a Domain Name Server (DNS)

  2. DNS looks up the IP address for the URL

  3. DNS returns the IP address to the web browser

  4. Web browser uses the IP address to access the website
• DNS servers are managed by global non-governmental organizations, but operated by ISPs and domain registrars
• HTTP (Hypertext Transfer Protocol)


  The main protocol for transmitting information on the World Wide Web, used to send requests and receive responses
• How HTTP works


  1. Web browser sends HTTP request to a server at a specific IP address

  2. Server responds with HTML, CSS, JavaScript files
• Sending a request to a URL


  1. Send request to DNS server

  2. DNS server returns IP address

  3. HTTP request sent to server with IP address
• Behind a single IP address there are hundreds of thousands or millions of computers that deal with incoming requests and return responses
• Receiving a response from a website


  1. Receive HTML, CSS, and JavaScript files

  2. Files displayed in web browser
• HTTP request


  Request sent to a web server
• HTTP response


  Response from web server containing HTML, CSS, and JavaScript
• Client is the web browser or user, server is the website being accessed
• Server-side scripting


  Code running on the server that processes requests and determines the HTML, CSS, and JavaScript to return
• Client-side scripting


  HTML, CSS, and JavaScript returned from the server and rendered in the web browser
• HTTPS


  Secure version of HTTP that encrypts data using SSL/TLS
• HTTPS connection establishment


  1. Server shares SSL/TLS certificate

  2. Browser verifies certificate

  3. Browser sends encrypted data using public/private key

  4. Server decrypts data using private key
• HTTPS URLs start with https:// to indicate a secure connection
• Port


  Number associated with a specific network service or protocol, allows multiple services to run on a server simultaneously
• Web browser


  Software application used to access and display content on the World Wide Web, including web pages
• Cookie


  Small text file stored in the user's web browser to track user preferences and activity
• Cookies can be used to track user behavior across multiple websites, raising privacy concerns
• HTML


  Hypertext Markup Language used to create web pages and other documents for display in a web browser
• HTML


  • Uses tags to indicate how content is displayed
  • Often combined with CSS and JavaScript in modern websites
• Web page


  Displayed in a web browser, with underlying HTML code that tells the web browser how to display the content
• HTML


  Used to structure content on web pages, provides a way to add text, images, multimedia, links and other content, based on a set of tags
• HTML tags


  • Indicate how content is displayed, such as headings, paragraphs, lists, tables, forms, etc.
• HTML is often used in conjunction with CSS and JavaScript in modern web pages</b>
• Client-side scripting


  HTML, CSS and JavaScript code executed in the web browser
• Server-side scripting


  Scripts or programming languages used to generate web pages on a web server
• Server-side scripting process


  1. User sends HTTP request to web server

  2. Server-side script processes the request

  3. Script accesses database data

  4. Script generates HTML, CSS and JavaScript

  5. Server sends HTTP response back to user
• Common Gateway Interface (CGI)


  Intermediary between web server and server-side script, accepts requests and executes scripts
• CGI has largely been replaced by language-specific solutions for executing server-side code and returning results to the user
• HTML document structure


  • HTML tags
  • Head section (contains information about the web page)
  • Body section (contains the content of the web page)
  • Footer section