Discuss the different types of storage devices used in computers.

1. 1 · Open in two lines. Storage holds data and programs. Primary memory supports the work in progress; secondary storage keeps data permanently.
2. 2 · Storage units. Bit, byte (8 bits), KB, MB, GB, TB, each 1,024 times the one before.
3. 3 · Primary memory.
   • RAM: working memory, volatile.
   • ROM: permanent start-up instructions.
   • Cache: very fast memory close to the CPU.
4. 4 · Magnetic storage.
   • Hard disks: large, cheap, direct access.
   • Tapes: very cheap backups, sequential access.
5. 5 · Optical storage. CD (about 700 MB), DVD (4.7 GB), Blu-ray (25 GB): read by laser, cheap and portable, but small and easily scratched.
6. 6 · Flash memory. USB drives, SSDs and memory cards: fast, no moving parts, shock-resistant; SSDs cost more per GB.
7. 7 · Sri Lankan business example. A bank keeps live accounts on fast disk and flash storage and sends backups to tape or another site.
8. 8 · Close in one line. Choose storage by capacity, speed, cost, portability and how long the data must last.

Scoring tip: A comparison table of magnetic, optical and flash earns quick marks.