Lecture Notes: Computer Architecture

Introduction

• Topic Focus: Computer Architecture (Topic 2)
• Comparison: Considered the most demanding among non-programming topics.
• Components: CPU, RAM, hard drives, OS.

Central Processing Unit (CPU)

• Role: Brain of the computer, handles processing of instructions.
• Operations: Arithmetic and logical operations.
• Example: Clicking an 'X' on a program triggers CPU execution.

How CPU Works

• Model: Von Neumann model.
• Process: Multi-step including program counter, memory address register (MAR), and memory data register (MDR).

Key Components and Processes

• Program Counter (PC):
  • Sends address to MAR.
  • MAR: Holds memory addresses, sends data to RAM.
  • RAM: Stores program data in addresses.
  • MDR: Receives data from RAM, sends to control unit.
• Control Unit (CU):
  • Decodes data for execution by Arithmetic Logic Unit (ALU).
  • Orchestrates Fetch-Decode-Execute (FDE) cycle.
• Arithmetic Logic Unit (ALU):
  • Executes operations, uses the accumulator for temporary storage.

Memory

Primary Memory

• RAM (Random Access Memory):
  • Volatile, non-persistent.
  • Stores program data temporarily.
• ROM (Read-Only Memory):
  • Permanent instructions, non-volatile.
  • Stores BIOS and fundamental boot instructions.

Secondary Memory

• Hard Drive:
  • Long-term, persistent storage.
  • Slower but larger storage compared to RAM.
• Virtual Memory:
  • Used when RAM is overloaded, slower as it uses hard disk.

Cache

• Role: Stores frequently used instructions closer to CPU.
• Benefit: Speeds up data retrieval, sits between CPU and primary memory.

Operating Systems

• Definition: Software controlling hardware resources, providing services.
• Roles: User interface, memory management, peripheral management, multitasking, security.
  • User Interface: GUI, CLI, Natural Language, Menu-based.
  • Memory Management: Allocates RAM, organizes data.
  • Peripheral Management: Uses device drivers.
  • Multitasking: Allocates CPU cycles.
  • Security: User permissions and file access.

Data Representation

• Binary and Bits:
  • Conversion: Binary to denary and vice versa.
  • Units: 1 byte = 8 bits, conversion hierarchy (kB, MB, GB, TB).
• Text Representation:
  • ASCII: 7 bits + parity bit, 128 characters.
  • Unicode: More bits, more languages.

Image and Color Representation

• Pixels: Grid of small squares on screens.
• Color Encoding: 6-digit hexadecimal codes for RGB values.

Logic Gates

• Concept: Takes one or two inputs (1 or 0) and outputs either a 1 or 0.
• Types: NOT, AND, OR, XOR, NAND, NOR.
  • NOT Gate: Inverts input.
  • AND Gate: Requires both inputs to be true for true output.
  • OR Gate: Requires at least one true input for true output.
• Truth Tables: Show all possible inputs/outputs.
• Chaining Gates: Combine gates for complex operations.

Hexadecimal and Binary

• Hexadecimal (Base 16):
  • Used for efficiently representing large binary values.
  • Conversion to/from binary.

Important Notes

• Exams: Familiarity with terms, processes, and conversions is crucial for the IB exam.
• Resources: Slides and additional materials available for further study.