TechTayari

S3 · Computer Studies I · Grade 10 · ages 15–16

Storage & the CPU

Memory, storage and the processor

Grade 10 · 1.4 Computer storage · 1.5 Central Processing Unit (CPU)CBE strandFree · works offline

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The full lesson adds narration, an interactive mission and a 10-question bank, and the quiz explains any mistakes.

Primary storage

Primary storage is memory the CPU uses directly. RAM holds the programs and data in use right now and is volatile: it is wiped when power goes off. ROM is non-volatile and holds start-up instructions (firmware). Cache is a small, very fast memory close to the CPU for data it needs again and again.

Secondary storage

Secondary storage keeps files when the power is off: hard disk drives (HDD) with spinning platters, solid-state drives (SSD) with no moving parts, USB flash drives and memory cards, optical discs (CD, DVD), and cloud storage on someone else's servers over the internet.

Measuring storage

1 byte is 8 bits. Storage sizes go kilobyte (KB), megabyte (MB), gigabyte (GB), terabyte (TB). In computing, each step is traditionally 1024 times the last (1 KB = 1024 bytes), though drive makers often use 1000. A photo might be 3 MB; a phone might store 128 GB.

Caring for storage

Back up important files in at least two places. Eject flash drives before pulling them out. Keep hard disks away from knocks, heat and strong magnets. Scan removable drives for malware, because they spread infections between computers.

Inside the CPU

The CPU has a Control Unit that directs the fetch–decode–execute cycle, an Arithmetic Logic Unit (ALU) that does calculations and comparisons, and registers: tiny, ultra-fast storage inside the CPU. Speed depends on clock speed (in GHz), the number of cores working in parallel, and cache size.

Key points

  • Primary storage is used directly by the CPU: RAM, ROM and cache.
  • RAM is volatile and forgets everything when the power goes off.
  • ROM keeps its start-up instructions even without power.
  • Secondary storage, like SSDs, hard disks and flash drives, keeps files long-term.
  • One byte is eight bits; then kilobytes, megabytes, gigabytes and terabytes.
  • Back up important files, and always eject flash drives safely.
  • Inside the CPU, the control unit directs, the ALU calculates, and registers hold data.

Try it for real: Inspect your storage

  • On a computer or phone, find how much storage is used and free (Settings › Storage).
  • Find the processor's speed in GHz and its number of cores (System Information or Settings › About).
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