Computer Science Notes

Chapter 1: Computer System

  • Computer: A device that receives input, processes it, and produces output.
  • Two main components of computers:
    • Hardware: Physical components of the computer.
    • External Hardware: Visible to the user (e.g., Mouse, Keyboard, Monitor).
    • Internal Hardware: Inside the computer (e.g., CPU, Motherboard, RAM).
    • Software: Programs controlling computer operations.
    • Application Software: Programs for user tasks (e.g., Word Processor).
    • System Software: Programs that allow the computer to run (e.g., OS).

Main Hardware Components

  • Central Processing Unit (CPU): Processes instructions and consists of:
    • Control Unit: Controls CPU interactions.
    • Arithmetic Logic Unit (ALU): Performs arithmetic and logical operations.
  • Main Memory: Directly accessible memory (e.g., RAM and ROM).
  • Backing Storage: Non-volatile storage (e.g., HDD, SSD).

Input and Output Devices

  • Input Devices: Enter data into the computer (e.g., Keyboard, Mouse).
  • Output Devices: Display or send data from the computer (e.g., Monitor, Printer).

Chapter 2 & 3: Input and Output Devices

  • Data Types:
    • Analogue Data: Continuous data (e.g., temperature).
    • Digital Data: Discrete data (0 and 1).
  • Converters:
    • ADC: Converts analogue to digital.
    • DAC: Converts digital to analogue.
  • Pointing Devices: Control on-screen pointer (e.g., Mouse, Touchpad).

Advantages & Disadvantages of Input Devices

  • Mouse: Faster than a keyboard but requires a flat surface.
  • Touchpad: More portable but harder to control than a mouse.
  • Tracker Ball: Requires less desk space, but needs training.
  • Keyboard: Fast data entry, but occupies more space.

Chapter 4: Storage Devices

  • Backing Up Data: Creating spare copies for retrieval in case of data loss.
  • Types of Storage:
    • Magnetic Media: (e.g., HDD) large capacity but less durable.
    • Optical Media: (e.g., CD, DVD) portable and cheaper but slower access.
    • Solid State Media: (e.g., SSD) faster access but more expensive.

Cloud Storage

  • Definition: Online storage allowing access from any device with internet.
  • Advantages: Accessible anywhere, more storage space, automatic backups.
  • Disadvantages: Requires internet, security concerns.

Chapter 5: Databases

  • Data Types:
    • Numeric Data: Includes integers, decimals, currency.
    • Alphanumeric Data: Letters and numbers combined.
    • Boolean Data: Two possible values (True/False).

Database Structures

  • Flat-File Database: Single table data storage.
  • Relational Database: Multiple linked tables using keys.
    • Primary Key: Unique identifier for records.
    • Foreign Key: Primary key from another table used to link tables.

Chapter 6: Networks

  • Definition of Network: Connection of two or more devices.
  • Advantages: Sharing resources and data, communication.
  • Disadvantages: Spread of viruses, security risks.
  • Types of Networks: LAN, WLAN, WAN.

Network Devices

  • NIC: Connects devices to a network.
  • Router: Routes data packets to specific destinations.
  • Switch: Directs data to destination devices.
  • Firewall: Filters traffic to protect the network.

Chapter 7: System Development Life Cycle

  • Phases: Analysis, Design, Development, Testing, Implementation, Documentation, Evaluation.
  • Importance of Testing: Ensures the system works as intended before live operation.
  • Documentation: Helps users and technical staff maintain the system.

Methods of Implementation

  • Parallel Running: New system runs alongside the old.
  • Direct Changeover: Old system replaced immediately.
  • Phased Implementation: New system introduced in stages.

Chapter 8: Effects of ICT

  • Copyright: Protects original works from unauthorized use.
  • Health Effects: Prolonged use of ICT can lead to eyestrain, back problems, RSI.

Security Issues

  • Malware: Harmful software aimed at corrupting or manipulating data.
  • Phishing: Fraudulent attempts to obtain sensitive information.
  • Spyware: Tracks user activity without their consent.

Chapter 9: ICT Systems

  • Monitoring Systems: Use sensors to constantly take readings.
  • Control Systems: Use sensors and actuators to take action that affects the environment.
  • Robots: Machines programmed to perform tasks.

Chapter 10: Banking Applications

  • Electronic Funds Transfer: Direct transfer between banks without cash.
  • Internet Banking: Convenience of accessing banking services online.
  • Payment Methods: Various methods including debit/credit cards and NFC payments.