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IB DP Computer Science Study Notes

C.1.2 Protocols and Standards

Protocols and standards are the pillars that sustain the framework of the Internet and the World Wide Web. They are the agreed-upon conventions that dictate how information is exchanged and processed across different systems, ensuring that the web remains a universally navigable and interoperable network. This segment examines the essential web elements which are fundamental to the Internet's functionality and efficiency.

HTTP (HyperText Transfer Protocol)

HTTP is the principal protocol used for transmitting web pages on the internet. It operates on a request-response model between clients and servers.

Characteristics of HTTP:

  • Stateless Nature: Every request is executed independently without any memory of prior interactions, simplifying server design.
  • Performance: Designed for quick retrieval of web resources.
  • Extensibility: New methods and headers can be introduced without affecting the existing infrastructure.

Purpose of HTTP:

  • Resource Exchange: Facilitates the exchange of resources (like HTML documents) over the web.
  • Communication: Acts as a communication protocol for web browsers and servers.


HTTPS adds a layer of security to HTTP by incorporating encryption protocols such as SSL/TLS.

Characteristics of HTTPS:

  • Encryption: Encrypts data to prevent eavesdropping and tampering.
  • Authentication: Establishes a secure connection by authenticating the accessed website.
  • Data Integrity: Ensures that the data transferred has not been altered or corrupted.

Purpose of HTTPS:

  • Security: Protects user data during transfer, crucial for sensitive transactions.
  • Trust: Instils trust in users when entering personal information online.

HTML (HyperText Markup Language)

HTML is the standard language for creating and structuring web page content.

Characteristics of HTML:

  • Element-based: Consists of elements that define different types of content.
  • Semantics: Tags such as `<header>`, `<footer>`, `<article>`, and `<section>` describe the structure and meaning of web content.

Purpose of HTML:

  • Content Structure: Organizes and formats text, images, and other media on web pages.
  • Web Development: Serves as the foundational markup language for web development.

URL (Uniform Resource Locator)

URLs provide the means to retrieve any resource on the web, such as a web page, an image, or a file for download.

Characteristics of URL:

  • Syntax Structure: A URL includes the protocol, the domain of the resource, the path, and optional parameters or anchors.
  • Uniformity: Provides a consistent way to locate resources on the web.

Purpose of URL:

  • Resource Identification: Specifies the location of a resource on the web.
  • Navigation: Directs browsers on how to retrieve a resource.

XML (eXtensible Markup Language)

XML is a flexible way to create common information formats and share both the format and the data on the World Wide Web or other networks.

Characteristics of XML:

  • Flexibility: Tags are not predefined, allowing for custom information structures.
  • Human-readable: The clear, structured format is both human and machine-readable.

Purpose of XML:

  • Data Transport: Serves as a tool for transporting and storing data.
  • Data Description: Describes data in a structured, rule-based manner.

XSLT (eXtensible Stylesheet Language Transformations)

XSLT is an XML-based language used for transforming XML documents into other document types.

Characteristics of XSLT:

  • Transformation: Changes the structure or style of XML documents.
  • Versatility: Capable of converting XML data into various formats such as HTML, text, or other XML documents.

Purpose of XSLT:

  • Data Presentation: Allows for styling and presenting XML data in different ways.
  • Customisation: Offers the ability to tailor the display of XML data for different devices or purposes.


JavaScript is a powerful scripting language that enables dynamic interactions on web pages.

Characteristics of JavaScript:

  • Interactivity: Adds interactivity to web pages such as games, responsive forms.
  • Asynchronous Processing: Allows for tasks like AJAX calls to run in the background without interrupting the user experience.

Purpose of JavaScript:

  • Enhancing User Experience: Improves the usability and responsiveness of web pages.
  • Client-Side Operations: Executes complex features on the client-side, reducing server load.

CSS (Cascading Style Sheets)

CSS is the language for describing the look and formatting of documents written in markup languages.

Characteristics of CSS:

  • Styling: Specifies how elements are displayed on screen, on paper, in speech, or on other media.
  • Cascading Rules: Multiple style sheets can influence the same piece of content, with one style "cascading" over another.

Purpose of CSS:

  • Visual Design: Controls the layout of multiple web pages with consistency.
  • Responsive Design: Enables web pages to adapt to different screen sizes and devices.

URI (Uniform Resource Identifier)

URI is a compact string of characters used to identify or name a resource on the Internet.

Characteristics of URI:

  • Locator or Name: Can be used as a locator (URL), a name (URN), or both.
  • Syntax: Comprises a scheme name followed by a string whose format is scheme-specific.

Purpose of URI:

  • Resource Identification: Provides a means for identifying a resource without ambiguity.
  • Uniformity: Ensures a standard format for addressing resources.

Significance of Protocols and Standards

Protocols and standards are not just technical tools; they represent a consensus among the global internet community.

Importance of Protocols:

  • Intercommunication: Allow different networks and devices to communicate.
  • Reliability: Provide stable and reliable frameworks for data exchange.

Importance of Standards:

  • Universal Access: Ensure that web technologies work across various platforms and devices.
  • Innovation: Standards provide a base upon which new technologies are developed.

Understanding these protocols and standards is not merely an academic exercise; it is an essential skill for any aspiring IT professional. They ensure that despite the vast and varied nature of the Internet, it remains a coherent and unified presence in the digital age, accessible and usable by all. These standards foster an environment where innovation can thrive, allowing for the development of new web technologies and applications that continue to revolutionize how we interact with the digital world.


HTTP being a stateless protocol means that each request from a client to server is treated as an independent transaction that is unrelated to any previous requests. This simplifies the server design as it does not need to retain session information. However, many web applications require the ability to maintain user state across multiple requests. To manage state, web applications use mechanisms like cookies, sessions, and tokens. Cookies are small pieces of data stored on the client's computer and sent with requests to the server, which can track state information like login status. Sessions track user state on the server side, often with a reference stored in a user's cookie. Tokens, such as JWT (JSON Web Tokens), can also be used to maintain state and handle authentication and authorisation across requests.

XSLT (eXtensible Stylesheet Language Transformations) is used in XML applications to transform XML documents into other formats, like HTML, text files, or even other XML documents with different schema. The purpose of XSLT is to enable the manipulation of XML data into a form suitable for display or further processing. For example, XSLT can be used to transform XML data into HTML for display on a web page, ensuring that the underlying data can be presented in a user-friendly format. Yes, XSLT can be applied to formats other than HTML. It is a versatile tool that can produce a variety of output formats from XML, making it valuable for numerous applications where different document types are required.

JavaScript enhances interactivity on websites by enabling dynamic content updates, user interface animations, form validation, and much more without the need for full page reloads. It responds to user actions like clicks, form submissions, and keyboard events, allowing web developers to create rich, interactive experiences. Examples of JavaScript usage include interactive maps, animated 2D/3D graphics, scrolling video jukeboxes, and real-time content updates like stock tickers or news feeds. JavaScript can manipulate the Document Object Model (DOM), allowing for the creation of dynamic and responsive user interfaces that improve engagement and user experience.

XML (eXtensible Markup Language) is considered extensible because it allows developers to define their own tags and data structures. This flexibility enables the creation of custom data formats tailored to specific needs. In web development, this extensibility means that XML can be used to define, exchange, store, and display data across various applications and services. It allows different systems to communicate and share data in a consistent way, despite differences in underlying technology. This interoperability is beneficial for complex web applications that involve data transactions between multiple platforms, making XML a powerful tool for developers who need a customisable and versatile data exchange format.

A URL (Uniform Resource Locator) is a specific type of URI (Uniform Resource Identifier) that not only names a resource but also provides a means to locate it by describing its primary access mechanism, e.g., its network location. All URLs are URIs, but not all URIs are URLs. A URI can be a name, a locator, or both for an internet resource. For example, a URL like `https://www.example.com/index.html` locates an HTML page on the internet. In contrast, a URI could be a URL for locating it or a URN (Uniform Resource Name) like `urn:isbn:0451450523`, which names a resource (in this case, by an ISBN) without suggesting where or how to locate it.

Practice Questions

Explain the role of HTTPS compared to HTTP and why it is critical for transactions that require confidentiality.

HTTPS, which stands for HyperText Transfer Protocol Secure, is essential for protecting sensitive communications over a computer network. Unlike HTTP, HTTPS provides a secure channel over which data can be transmitted safely. This security is achieved through the use of SSL/TLS protocols, which encrypt the data sent between the client and the server. Encryption is critical for confidential transactions as it ensures that sensitive information, such as credit card numbers or login credentials, cannot be intercepted or read by unauthorised parties. Moreover, HTTPS also authenticates the visited website, ensuring that the user's communication only goes to the intended recipient, which helps in preventing 'man-in-the-middle' attacks. Hence, for any transactions requiring confidentiality, HTTPS is indispensable for ensuring data privacy and security.

Describe the purpose of CSS in web development and how it impacts the user experience on a website.

Cascading Style Sheets (CSS) are used to define the presentation of web documents written in HTML and XML. CSS separates the content of a web page from its stylistic elements, enabling developers to create visually engaging and consistent interfaces across multiple web pages. By using CSS, developers can control the layout, colour, fonts, and other visual aspects of a web page, enhancing the overall aesthetic and functional experience for users. Moreover, CSS is instrumental in creating responsive designs that adapt to different screen sizes and devices, thereby improving accessibility and ensuring a uniform user experience. This separation of content and style streamlines web development, allows for quicker page loads, and facilitates the maintenance and updating of web pages.

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Written by: Alfie
Cambridge University - BA Maths

A Cambridge alumnus, Alfie is a qualified teacher, and specialises creating educational materials for Computer Science for high school students.

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