Lecture Notes: Hardware - Types of Memory & Storage

Introduction

• Memory and storage devices are divided into three groups:
  1. Primary memory
  2. Secondary storage
  3. Off-line storage

1. Primary Memory

• Primary memory is directly accessible by the CPU and internal to the computer.
• Characteristics:
  • Fast access speed
  • Stores boot-up instructions
  • Volatile and non-volatile types
• Examples: RAM and ROM

a) RAM (Random Access Memory)

• Features:
  • Volatile/temporary memory
  • Stores current instructions, programs, and data
  • Read and write capability
  • Fastest type of memory
  • Larger than ROM
• Types:
  • Dynamic RAM (DRAM): Requires constant refreshing
    • Advantages: Cheaper, less power, higher capacity
  • Static RAM (SRAM): Faster access, used in caches

b) ROM (Read-Only Memory)

• Features:
  • Non-volatile/permanent memory
  • Stores startup instructions (e.g., BIOS)
• Types:
  • PROM, EPROM, EEPROM

2. Secondary Storage

• Not directly accessible by CPU; non-volatile
• Examples: HDD and SSD

a) Hard Disk Drives (HDD)

• Data storage: Magnetic surfaces of the disk
• Advantages: Cheaper, higher longevity
• Disadvantages: Slow access, latency issues

b) Solid State Drives (SSD)

• Data storage: Semiconductors, NAND/EEPROM technology
• Advantages: Faster, reliable, lower power
• Disadvantages: Expensive

3. Off-line Storage

• Removable, non-volatile, not directly accessed by CPU
• Examples:
  • Optical: CDs, DVDs
  • Solid state: USB flash drives, SD/XD cards
  • Magnetic: Removable HDD

Input Devices

• Microphones: Convert sound to electrical signal
• Screens: LCD, LED, OLED technologies
• Touchscreens: Capacitive, Infra-red, Resistive
• Sensors: Various types for monitoring and control

Output Devices

• Printers: Inkjet, Laser
• 3D Printers: Uses CAD, additive manufacturing
• Loudspeakers: Convert digital to analog sound

Key Terms & Concepts

• Volatile vs Non-volatile memory
• RAM vs ROM
• DRAM vs SRAM
• Primary vs Secondary storage
• Optical vs Solid state storage

Applications & Use Cases

• Embedded Systems: Specific tasks, used in appliances and vehicles
• Differences in storage technologies: Cost, speed, durability

Exam Practice Questions

• Differences between RAM and ROM
• Reasons for using SSD over HDD and vice versa
• Role of sensors in systems

This summary covers the essential aspects of memory and storage types, input/output devices, and their applications, useful for exam preparation and understanding the core concepts of computer hardware.