This lesson covers how the internet works and how we use it for communication. It's about understanding the addresses, rules, and services that make the global network function.

Short Notes

• Internet Addresses:

  • IP Address (Internet Protocol): A unique numerical address for every device on the internet (e.g., 192.168.1.1). This is for computers to understand.

  • Domain Name: The text-based name we use to remember websites (e.g., www.nie.lk). This is for humans to remember.

  • URL (Uniform Resource Locator): The full address of a specific resource on the web (e.g., http://www.nie.lk/index.html).

• DNS (Domain Name System): The "phonebook of the internet." A DNS server's job is to translate human-friendly domain names into computer-friendly IP addresses.

• Client-Server Model: Your computer (the client) requests information (like a webpage) from a powerful computer (the server) that stores and serves the information.

• Protocols: The rules that govern communication on the internet. Key ones are:

  • HTTP (Hypertext Transfer Protocol): For viewing webpages.

  • FTP (File Transfer Protocol): For uploading and downloading files.

  • TCP/IP (Transmission Control Protocol/Internet Protocol): The fundamental protocol for sending data packets.

• Electronic Mail (Email):

  • Email Address: Has two parts: username@domainname (e.g., student@gmail.com).

  • To: The main recipient.

  • Cc (Carbon Copy): For recipients who need to see the email but aren't the primary audience. Everyone can see the Cc list.

  • Bcc (Blind Carbon Copy): For recipients you want to hide from others. No one can see the Bcc list except the person who is on it.

  • Attachment: A file sent along with an email.

  • Spam: Unwanted or junk email.

Important Points for the Exam

• Be able to identify the different parts of a URL (protocol, domain name, top-level domain, path, resource).

• Clearly explain the difference between an IP Address and a Domain Name, and the role of the DNS server in connecting them.

• The difference between Cc and Bcc is a very common question. Make sure you understand it perfectly.

• Know the meaning of key acronyms: URL, IP, DNS, HTTP, FTP.

Tips & Tricks for Studying

• Analyze URLs: Take the web address of your favourite websites and break them down into their parts. What is the protocol? What is the top-level domain (.lk, .com, .org)?

• Visualize the DNS Process: Imagine you want to call a friend. You look up their name (domain name) in your phone's contacts to find their number (IP address). The DNS works exactly like that.

Practice with Email: Send an email to yourself or a friend. Put one address in 'Cc' and another in 'Bcc' to see the result. This will solidify your understanding of how they work.