IGCSE Computer Science Chapter 3: Hardware

Introduction

• Focus on CPU and its functionalities.
• Misconception: CPU is not the desktop or laptop but a chip responsible for executing instructions.

CPU (Central Processing Unit)

• Executes instructions and processes data in computer applications.
• Example from gaming: Shooting in a game involves multiple instructions like reducing bullet count and enemy's health.

Von Neumann Architecture

• CPU works via Von Neumann architecture.
• Components:
  • CPU
  • Memory Unit (RAM)
  • Input/Output Devices

Components of Von Neumann Architecture

Arithmetic and Logic Unit (ALU)

• Performs arithmetic operations: addition, subtraction, multiplication, division.
• Conducts logical operations for decision-making.
• Possible to have multiple ALUs for different tasks.

Memory Unit (RAM)

• Temporary storage for instructions and data.
• Faster read/write operations than hard disks.
• Volatile memory: data lost when power is off.

Registers

• Fundamental components in Von Neumann architecture.
• Store instructions and results:
  • Current Instruction Register (CIR)
  • Accumulator (stores ALU results)
  • Memory Address Register (MAR)
  • Memory Data Register (MDR)
  • Program Counter (PC)

Control Unit

• Controls operations in the CPU.
• Sends signals via control bus.

Buses

• Facilitate communication between CPU components:
  • Address Bus: Carries addresses.
  • Data Bus: Carries data.
  • Control Bus: Carries control signals.
• Wider buses carry more data.

Fetch-Decode-Execute Cycle

• Method for CPU to process data quickly.
• Steps:
  1. Fetch: Retrieve instructions from memory.
  2. Decode: Interpret instructions.
  3. Execute: Process instructions.
• Involves different registers and buses.

Factors Affecting Computer Speed

• Clock Speed: Number of cycles per second—higher speeds increase performance.
• Cores: Multiple cores (e.g., dual-core, quad-core) allow parallel processing.
• Cache Memory: Stores frequently accessed data for faster retrieval.

Instruction Set and Embedded Systems

Instruction Set

• Set of instructions for CPU operations.
• Consists of opcodes (operational codes) and operands.

Embedded Systems

• Specific task-oriented computers embedded in devices.
• Examples: vending machines, lighting systems.

Input Devices

• Allow user interaction with computers.
• Examples:
  • Keyboard: For inputting text.
  • Mouse: Pointing device.
  • Touchscreen: Direct interaction interface.
  • Scanners: Convert physical documents into digital form.
• Different types of touchscreens (capacitive, resistive, infrared) have varying functionalities and uses.

Sensors

• Automatic input devices detecting environmental changes.
• Types: Temperature, Moisture, Humidity, Light, Infrared, Pressure, Sound, Gas, pH, Magnetic Field, Accelerometer, Proximity, Flow, Level.
• Applications include monitoring and control systems.
• Use ADC and DAC converters for data processing.

Data Storage

• Primary Memory (RAM/ROM):
  • RAM: Volatile, temporary storage.
  • ROM: Non-volatile, stores startup instructions.
• Secondary Storage:
  • HDD: Magnetic storage, slower due to mechanical parts.
  • SSD: Faster, no moving parts, flash storage.
  • Optical Media: CD, DVD, Blu-ray using laser technology.
  • Virtual Memory: Extends RAM capacity using disk space.
  • Cloud Storage: Online data storage solution.

Network Hardware

• Connects computers to networks.
• Network Interface Card (NIC): Allows device connection to a network.
• Router:
  • Connects networks and directs data.
  • Each device connected to a router has unique IP/MAC addresses.
• IP Address: Unique identifier for devices on a network (IPv4 and IPv6).
• MAC Address: Specific identifier for devices within a local network.

These notes summarize the key points of Chapter 3 on hardware, covering the CPU, its components, the operation cycle, factors affecting speed, instruction sets, input devices, sensors, data storage, and network hardware. Each section provides a foundation for understanding how computers operate and interact with users and networks.