Memory and storage: RAM, ROM and secondary storage

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교육자를 위해: Memory and storage: RAM, ROM and secondary storage(KS3 Computing, Computer Systems)을(를) 위한 바로 쓸 수 있는 수업 슬라이드, 복습 노트, 다이어그램 — 수업에 사용하거나, 학습자들이 실시간 게임으로 즐기는 인터랙티브 클래스 활동으로 진행하세요.

수업 노트

What is Computer Memory?

  • Computer memory stores data and programs for immediate use by the computer.
  • Memory is also called main memory or primary storage.
  • RAM (Random-Access Memory) is the most common type of main memory.
  • Main memory is fast but more expensive per bit and has lower capacity than mass storage.
  • Memory holds open programs and data being actively processed.
  • Operating systems use spare RAM as a cache to speed up reading and writing.

RAM: Volatile Working Memory

  • RAM stands for Random-Access Memory.
  • RAM is volatile: it loses its contents when power is off.
  • RAM is used for temporary storage of running programs and data.
  • The two main types of RAM are DRAM (dynamic) and SRAM (static).
  • DRAM is used for primary storage (main memory).
  • SRAM is used mainly for CPU cache because it is faster but more expensive.

ROM: Non-Volatile Start-Up Memory

  • ROM stands for Read-Only Memory.
  • ROM is non-volatile: it keeps its data even when power is off.
  • ROM contains start-up instructions (firmware) that the computer uses when it boots.
  • ROM is usually read-only, meaning data cannot be easily changed.
  • Other non-volatile memories include PROM, EPROM, and EEPROM.

Secondary Storage

  • Secondary storage is non-volatile storage for keeping data long-term.
  • It is slower than main memory but cheaper per bit and has higher capacity.
  • Common types: magnetic, optical, and solid-state.
  • Magnetic storage (e.g., hard disk drives) uses magnetised spots on spinning platters.
  • Optical storage (e.g., CDs, DVDs) uses lasers to read/write pits on discs.
  • Solid-state storage (e.g., SSDs, USB flash drives) uses flash memory with no moving parts.

Hard disk drive mechanism

Hard disk drive mechanism

Comparing Storage Types

  • Speed: RAM is fastest, then solid-state, then magnetic, then optical.
  • Cost: RAM is most expensive per GB, then solid-state, then magnetic, then optical.
  • Capacity: Secondary storage typically has much larger capacity than RAM.
  • Portability: Optical discs and USB flash drives are highly portable; internal HDDs/SSDs are less so.
  • Volatility: RAM is volatile; ROM and secondary storage are non-volatile.

Solid-state drive architecture

Solid-state drive architecture

Why a Computer Needs All Three

  • RAM provides fast, temporary workspace for running programs.
  • ROM ensures the computer can start up even when no other software is loaded.
  • Secondary storage saves data permanently for future use.
  • Without RAM, the CPU would have to use slow storage, making the computer very slow.
  • Without ROM, the computer wouldn't know how to boot.
  • Without secondary storage, you couldn't save files or install programs permanently.

How Memory is Organised

  • Memory is made of memory cells, each storing one bit (0 or 1).
  • Cells are grouped into words of fixed length (e.g., 8, 16, 32, 64 bits).
  • Each word has a unique binary address of N bits, allowing 2N words to be stored.
  • Modern memory uses semiconductor technology on integrated circuits.
  • Flash memory can store multiple bits per cell (multi-level cells).

Cache holds frequently needed data close to the CPU, so a hit avoids the slower trip to main memory.

Cache holds frequently needed data close to the CPU, so a hit avoids the slower trip to main memory.

Historical Context (Brief)

  • Early computers used vacuum tubes (e.g., ENIAC) with tiny capacity.
  • Delay-line memory used sound waves in mercury to store bits.
  • Magnetic-core memory was the first non-volatile memory and dominated until the 1970s.
  • MOS semiconductor memory (invented in the 1960s) was cheaper and faster, replacing magnetic core.

Closer to the CPU means faster and smaller; further away means larger, slower and cheaper per bit.

Main memory holds work in progress and is lost when power goes off; secondary storage keeps files permanently.

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연습 문제

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  1. 1.What does RAM stand for?

    Easy
    • ARead-Only Memory
    • BRandom-Access Memory
    • CRapid-Access Memory
    • DRandom-Access Module

  2. 2.RAM is volatile memory, meaning it loses its contents when the power is turned off.

    Easy

    True or false?

  3. 3.Which type of memory is used to store the start-up instructions that a computer needs when it is first turned on?

    Easy
    • ARAM
    • BROM
    • CSecondary storage
    • DCache

  4. 4.ROM is a type of non-volatile memory.

    Easy

    True or false?

  5. 5.Which of the following are characteristics of secondary storage compared to RAM? (Select all that apply)

    Medium
    • AIt is slower
    • BIt is less expensive per bit
    • CIt has higher capacity
    • DIt is volatile
    • EIt is used for long-term storage

  6. 6.Which of the following is an example of a solid-state storage device?

    Easy
    • AHard disk drive
    • BCD-ROM
    • CUSB flash drive
    • DFloppy disk

  7. 7.Magnetic storage is generally more portable than solid-state storage.

    Easy

    True or false?

  8. 8.Match each type of memory/storage with its correct description.

    Medium
    • RAM
    • ROM
    • SSD
    • Volatile main memory
    • Non-volatile start-up memory
    • Solid-state secondary storage

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