Comprehensive Revision of SS1, 2 and 3 SS3 Digital Technologies Lesson Note

Everything in computing starts with the physical stuff you can touch.

• The CPU (Central Processing Unit): Often called the “Brain.” It has two main parts:
  1. ALU (Arithmetic Logic Unit): Does the math and logic (Is 5 > 3?).
  2. CU (Control Unit): The traffic warden that tells data where to go.
• Memory vs. Storage: * RAM (Volatile): The computer’s “Short-term memory.” It disappears when the power goes out.
  1. Hard Drive/SSD (Non-volatile): The “Long-term memory.” It keeps your files safe even when the computer is off.

Revision Tip: Remember that Input (Keyboard, Mouse, Scanner) goes in, Processing (CPU) happens, and Output (Monitor, Printer, Speakers) comes out.

Software – The Invisible Instructions

Hardware is useless without Software. We divide software into two main families:

1. System Software: This is the “Foundation.” The most important one is the Operating System (OS) like Windows, Android, or macOS. Without an OS, the computer won’t even start. It also includes Utility Software like Antivirus or Disk Cleaners.
2. Application Software: These are the “Tools” we use to get work done.
   1. Word Processors (MS Word) – for letters.
   2. Spreadsheets (MS Excel) – for calculations.
   3. Database (MS Access) – for organized records.
   4. Graphics (CorelDraw/Photoshop) – for design.

Networking – How the World Connects

A network is just two or more computers connected to share resources.

• PAN (Personal): Your phone connected to your Bluetooth headphones.
• LAN (Local): Computers in your school lab or home.
• WAN (Wide): The Internet (the biggest WAN in the world).

Topologies (The Shapes):

• Star: Everything connects to a central “Hub.” (Most common today).
• Bus: Everything connects to one single long cable.
• Ring: Each computer is connected to two others in a circle.

Protocols: Remember HTTP for websites and SMTP for emails. These are just the “rules” for how data travels.

Logic, Algorithms & Programming

This is the “Thinking” part of the syllabus. Computers don’t understand English; they understand Logic.

• Logic Gates: AND (needs both), OR (needs either), NOT (reverses it).
• Algorithms: A step-by-step plan to solve a problem.
• Flowcharts: The “Map” of an algorithm.
  1. Decision (Diamond): Used for “If” questions.
  2. Process (Rectangle): Used for calculations.

Programming Languages:

• Low-Level: Machine language (1s and 0s) — hard for humans, easy for computers.
• High-Level: Python, BASIC, Java — easy for humans, needs a Compiler or Interpreter to translate it for the computer.

Data Security & Ethics (Staying Safe)

As we move into a digital world, we have to protect our “Digital Lives.”

• The Threat: Viruses, Worms, and Trojans. These are pieces of code designed to steal or destroy data.
• The Defense: * Antivirus: Scans and removes “bad” code.
  1. Firewall: Blocks unauthorized people from entering your network.
  2. Encryption: Scrambling your data so only the person with the “Key” can read it.

Computer Ethics:

• Don’t use computers to steal or harm others.
• Respect Copyright (don’t pirate software or music).
• Avoid Plagiarism (always give credit if you use someone else’s information).

Final Summary: To pass your exam, focus on definitions, functions (what does it do?), and comparisons (how is A differentfrom B?).