Describe the purpose of a web browser, and give examples.

A web browser is a software application that allows users to access and interact with information on the World Wide Web. Its primary purpose is to retrieve, display, and navigate web pages. Here's a technical breakdown of the main functions and components of a web browser:

  1. User Interface (UI):
    • Address Bar: This is where users can input the URL (Uniform Resource Locator) or web address they want to visit.
    • Back and Forward Buttons: Allow users to navigate backward and forward through previously visited pages.
    • Reload/Refresh Button: Reloads the current web page, fetching the latest version from the server.
    • Home Button: Takes users to their designated homepage.
    • Tabs: Allow users to open multiple web pages simultaneously within the same browser window.
  2. Rendering Engine:
    • This is the core component responsible for interpreting and rendering HTML (Hypertext Markup Language), CSS (Cascading Style Sheets), and JavaScript code.
    • Examples of rendering engines include:
      • Blink (used in Google Chrome): Developed by Google, based on the open-source Chromium project.
      • WebKit (used in Safari): Originally developed by Apple, now also used by some other browsers.
      • Gecko (used in Mozilla Firefox): Developed by the Mozilla Foundation.
  3. Networking:
    • The browser communicates with web servers using protocols such as HTTP (Hypertext Transfer Protocol) and HTTPS (HTTP Secure).
    • Handles tasks like DNS resolution to convert human-readable domain names into IP addresses.
    • Manages the retrieval of web page resources like images, stylesheets, and scripts.
  4. Browser Engine:
    • Coordinates actions between the UI and the rendering engine.
    • Manages user input like mouse clicks and keyboard inputs.
  5. JavaScript Engine:
    • Executes JavaScript code embedded in web pages.
    • Examples include:
      • V8 (used in Google Chrome): Developed by Google.
      • SpiderMonkey (used in Mozilla Firefox): Developed by the Mozilla Foundation.
  6. Storage:
    • Browsers store various types of data, including cookies, cache, and user preferences.
    • Cookies are small pieces of data sent from a website and stored on the user's computer.
  7. Security Features:
    • Same-Origin Policy: Prevents web pages from making requests to a different domain than the one that served the web page.
    • HTTPS: Ensures secure communication between the browser and the web server by encrypting data.

Examples of web browsers include:

  • Google Chrome: Uses the Blink rendering engine.
  • Mozilla Firefox: Uses the Gecko rendering engine.
  • Microsoft Edge: Uses the Blink rendering engine (previously used EdgeHTML).
  • Apple Safari: Uses the WebKit rendering engine.