Welcome to Internet Services and Applications!

Hey everyone! Ever wondered how you can watch a YouTube video, search for homework answers, and chat with your friends online all at the same time? It's all thanks to the amazing services and applications running on the Internet. In this chapter, we're going to explore how the web works behind the scenes. Understanding this is super useful for your daily life and will make you a much smarter and more efficient Internet user. Don't worry if some of the terms seem new; we'll break everything down into simple, easy-to-understand parts. Let's dive in!


1. How the Web Delivers Information to You

When you browse a website, it feels instant, but there's a fascinating step-by-step process happening in the background. Let's look at the key players that make this happen.

What is a URL?

A URL (Uniform Resource Locator) is simply the address of a specific webpage or file on the Internet. It tells your browser exactly where to go to find what you're looking for.

Analogy: Think of a URL like a full home address. It has the country, city, street, and house number to guide you to a unique location. For example, `https://www.example.com/page.html` is a complete address for a specific page.

DNS: The Internet's Phonebook

Computers on the Internet don't use names like `www.google.com` to find each other. They use numbers called IP addresses (e.g., `142.250.191.78`). So how does your browser know which number belongs to which website name? That's the job of the DNS (Domain Name System).

DNS is like a giant, super-fast phonebook for the Internet. It translates the human-friendly domain names (like `www.hkeaa.edu.hk`) into computer-friendly IP addresses.

How DNS Works (Step-by-Step):

1. You type a URL like `www.example.com` into your browser and press Enter.
2. Your computer sends a request to a DNS server, asking, "What is the IP address for www.example.com?"
3. The DNS server looks up the name in its directory and finds the matching IP address.
4. The DNS server sends that IP address back to your computer.
5. Your browser now knows the correct address and can connect to the website's server to request the webpage.

Memory Aid: Think DNS = Does Name Searching.

HTTP and HTTPS: The Language of the Web

Once your browser knows the server's IP address, it needs to communicate with it. They do this using a special set of rules, or a protocol.

HTTP (Hypertext Transfer Protocol) is the fundamental protocol used by the World Wide Web. It's the language browsers use to send requests to web servers and for servers to send web content back.

HTTPS (Hypertext Transfer Protocol Secure) is the secure version of HTTP. When you see `https` and a padlock icon in your browser's address bar, it means the communication between your browser and the website is encrypted. This is super important for protecting sensitive information like passwords, credit card numbers, and personal details.

Analogy: Think of HTTP as sending a postcard. Anyone who intercepts it can read the message. HTTPS is like sending the same message in a sealed, locked box that only the recipient has the key for. It's private and secure.

Quick Review Box

URL: The web address of a page.
DNS: Translates website names into IP addresses.
HTTP: The protocol for requesting and sending web pages.
HTTPS: The SECURE version of HTTP. Always look for the 'S' when entering sensitive data!

Key Takeaway

To view a website, your browser uses a URL to ask a DNS server for the site's IP address. It then uses HTTP or HTTPS to request the webpage from that address. HTTPS provides a crucial layer of security through encryption.


2. Becoming a Web Detective: Search and Analysis

The Internet has a mind-boggling amount of information. Finding exactly what you need and knowing if you can trust it are essential skills.

Formulating an Effective Search Strategy

Just typing one or two words into a search engine is okay, but you can get much better results with search operators and structured strategies:

  • Boolean Operators: Use AND, OR, and NOT to combine or exclude search terms.
    • AND: Narrows the search by requiring both words (e.g., robotics AND education).
    • OR: Broadens the search by finding pages containing either word (e.g., DSE OR exam).
    • NOT (or minus sign -): Excludes unwanted keywords (e.g., mustang NOT car or mustang -car).

  • Quotation Marks for Exact Phrases: Searching for "climate change in Hong Kong" returns only pages where the words appear in that exact sequence.

  • Wildcards (*): Using an asterisk replaces unknown words or variations in a phrase (e.g., "a * saved is a * earned").

  • Being Specific: Instead of searching for just "camera", try "best budget mirrorless camera for beginners 2024".

Critically Analysing Information Sources

Not everything you read online is true! It's important to be a critical thinker and evaluate the information you find. Before you trust a source, ask yourself these questions:

  • Who is the author? Are they an expert on the topic? A government body? A company trying to sell you something? (e.g., A health article from a university's medical school is generally more reliable than one from a random blog.)

  • What is the purpose of the website? Is it to inform, persuade, entertain, or sell a product? This can reveal potential bias. (e.g., A product review on the manufacturer's own website will likely be biased.)

  • When was it published? Is the information up-to-date? This is very important for topics in science, technology, and current events.

  • Can I verify the information? Are there links to original sources? Can you find similar information on other reputable websites?

Key Takeaway

To find reliable information, use a specific search strategy (with Boolean operators, exact phrases, and wildcards) to narrow down your results. Then, always critically analyse the source to check for authority, bias, and accuracy before trusting the information.


3. Multimedia on the Web

The modern web is full of images, videos, and sounds. These elements are stored in different file formats using lossy compression (which discards some unnoticeable data to achieve smaller file sizes) or lossless compression / uncompressed data (which preserves exact original quality).

Common Multimedia File Formats

Different file types are used for different media because they are optimised for quality, file size, and features.

  • Graphics:
    • JPG (or JPEG): Uses lossy compression. Ideal for photographs because it significantly reduces file size while retaining good visual quality.
    • PNG: Uses lossless compression. Excellent for logos, illustrations, and images that require transparency.
    • GIF: Uses lossless compression with a limited colour palette (up to 256 colours). Commonly used for simple web animations.

  • Audio:
    • MP3: Uses lossy compression. It is the most popular audio format for web streaming and music storage because of its small file size.
    • WAV: Standard uncompressed (lossless) audio. It delivers pristine audio quality but has very large file sizes, making it less practical for regular web pages.

  • Video:
    • MP4 (or MPEG-4): A highly compressed format delivering an excellent balance of video quality and file size. It is the industry standard for online video streaming.
    • AVI: An older video container format that tends to have larger file sizes, making it less ideal for modern web streaming.

Plug-ins and Players

A plug-in is a small piece of software that adds extra functionality to a program, like a web browser. In the past, you needed to install plug-ins like Adobe Flash Player to watch videos or play games.

Today, modern web browsers have most of the necessary multimedia players built-in thanks to technologies like HTML5. This means you can usually watch videos, listen to audio, and view PDFs directly in your browser without installing anything extra!

Did you know?

The creator of the GIF format, Steve Wilhite, insisted that it is pronounced "JIF" with a soft 'g', like the peanut butter brand. However, the debate rages on, and many people still pronounce it with a hard 'g'!

Key Takeaway

Web pages use different file formats (lossy vs. lossless/uncompressed) to handle multimedia efficiently. While plug-ins used to be essential, most modern browsers can now play this content directly using built-in HTML5 players.


4. Essential Internet Services

The World Wide Web (websites) is just one part of the Internet. There are many other fundamental services we use every day.

  • Email (Electronic Mail): Allows you to send and receive digital messages and attachments over a network asynchronously.

  • File Transfer: Services like FTP (File Transfer Protocol) allow users to upload and download files between computers, such as uploading website assets to a remote server.

  • Remote Logon: Allows a user to log into and securely control another computer from a distance (e.g., using SSH - Secure Shell).

  • Online Chat: Enables real-time text, voice, or video conversation between two or more people (e.g., WhatsApp Web, Discord).

  • Discussion Forum: An online message board where users hold discussions by posting messages organized into topics and threads (e.g., Reddit, LIHKG).

  • Newsgroup: An online repository/bulletin board within Usenet where users post and read articles or messages related to specific topics of interest.

Key Takeaway

Beyond browsing websites, the Internet provides essential services for communication and data exchange, including email, file transfer, remote logon, online chat, discussion forums, and newsgroups.


5. The Magic of Streaming

Why can you start watching a Netflix movie instantly instead of waiting for the entire two-hour film to download? The answer is streaming!

The Concept of Streaming Technology

Streaming is a method of transmitting data (usually audio and video) as a continuous, steady flow. Your device starts playing the content as it arrives, while the rest of the file continues to be delivered in the background.

This is different from a traditional download, where you must wait for the entire file to be saved on your device before you can open it.

Analogy: Downloading is like filling up a bathtub completely before you can get in. Streaming is like turning on the shower – you can get in and start using the water as it flows, without waiting for the tub to fill up.

(Syllabus Note: You only need to understand the concept of streaming, not the complex technical details behind it. So don't worry about the 'how'!)

Applications of Streaming

Streaming technology powers many of the services we use daily:

  • Voice Mail: Modern voicemail systems, especially those on messaging apps (like WhatsApp voice notes), often use streaming to let you listen to the message as it downloads.

  • Videoconferencing: Services like Zoom, Google Meet, and Microsoft Teams stream live video and audio data between participants, allowing for real-time, face-to-face communication over the Internet.

  • Webcasting: This is essentially "broadcasting over the web". It involves streaming a live event (like a concert, a sports match, or a company announcement) to a large audience online.

Key Takeaway

Streaming allows you to play media content as it is being delivered, without waiting for a full download. This powerful technology is the foundation for popular applications like videoconferencing and webcasting.