This page will cover Chapter 3 of the IGCSE ICT syllabus by identifying storage devices, their associated media and their uses. It will also describe the advantages and disadvantages of devices such as hard drives, CDs, DVDs and Solid State Drives (SSD). Read the syllabus below to get a better understanding of what aspects of the course you need to understand for this unit. You can then read more about the theory further down. If you need teaching resources, click here to skip to them.

---

More Information

A. Magnetic Storage

• How it Works: Uses magnetic fields to represent binary data (0s and 1s).
• Examples: Hard disk drives (HDDs), portable hard drives, magnetic tapes.
• Uses: General-purpose storage, backups, archiving large volumes of data.
• Advantages: Large capacity, relatively fast access (especially HDDs), cost-effective for bulk storage.
• Disadvantages: Moving parts make them vulnerable to damage, slower than SSDs, magnetic fields can cause data loss.

B. Optical Storage

• How it Works: Uses lasers to burn patterns into the surface of a disc, creating pits and lands that represent data.
• Examples: CD, DVD, Blu-ray.
• Uses: Audio/video storage, software distribution, backups.
• Advantages: Affordable, portable, widely compatible.
• Disadvantages: Lower capacity than magnetic and solid state, susceptible to scratches, slower access speeds.

C. Solid State Storage

• How it Works: Stores data using electronic circuits, with no moving parts.
• Examples: Solid state drives (SSD), USB memory sticks, SD cards.
• Uses: Fast internal storage, portable data transfer, cameras, smartphones.
• Advantages: Fast access speeds, durable, portable, no moving parts.
• Disadvantages: More expensive per GB, limited write cycles (especially for USB sticks and SD cards).

Typical Uses and Access Types

• Magnetic Tape: Used for backups and archives; uses serial (sequential) access, which is slow but efficient for large, infrequently accessed data.
• Hard Disk Drives: Used for operating systems, applications, and files; uses direct (random) access, allowing quick retrieval of data.
• Optical Discs: Used for media distribution and backups; mostly direct access, but slower than hard drives.
• Solid State Devices: Used for fast storage and transfer; direct access, very quick read/write speeds.

Advantages and Disadvantages Comparison

Device/Media	Advantages	Disadvantages
Hard Disk Drive	Large capacity, fast access	Vulnerable to shock, moving parts
Magnetic Tape	High capacity, low cost	Slow, sequential access, vulnerable to magnets
CD/DVD/Blu-ray	Cheap, portable, widely compatible	Low capacity, easily scratched, slower access
SSD	Very fast, durable, no moving parts	Expensive, limited write cycles
USB Stick/SD Card	Small, portable, fast	Easy to lose, expensive per GB

Backups and the Need for Backing Storage

• Backup: The process of copying files to a different location (disk, tape, cloud, etc.) to protect against data loss due to hardware failure, corruption, accidental deletion, or security breaches.
• Backing Storage vs. Main Memory:
  • Main/Internal Memory (RAM): Volatile, fast, temporary storage used while the computer is running.
  • Backing Storage: Non-volatile, permanent, used for long-term storage of data and programs.

Key Terms

• Backing Storage: Another term for secondary storage; refers to any non-volatile device used to store data when not in use by RAM.
• Serial/Sequential Access: Data is accessed in order, from beginning to end (e.g., magnetic tape).
• Direct/Random Access: Data can be accessed directly at any point (e.g., hard drives, SSDs, CDs)

---

Exam Questions

Complete these in your notebooks as extension activities once you are finished. Did you know, practice exam questions will tell you topics you have mastered along with providing you with an insight into the types and structures of questions you are likely to receive in your exams?