Know and understand differences between backing storage and internal memory

Published by Patrick Mutisya · 14 days ago

ICT 0417 – Types and Components of Computer Systems

Types and Components of Computer Systems

Objective

Know and understand the differences between backing storage and internal memory.

Key Definitions

  • Internal Memory (Primary Memory) – Memory that is directly accessed by the CPU. It includes RAM (Random‑Access Memory) and ROM (Read‑Only Memory).

  • Backing Storage (Secondary Storage) – Non‑volatile devices used to store data permanently, such as hard‑disk drives, solid‑state drives, optical discs and magnetic tapes.

Comparison of Backing Storage and Internal Memory

AspectInternal MemoryBacking Storage
PurposeTemporarily holds data and instructions that the CPU is currently processing.Provides long‑term, permanent storage of programs, files, and system data.
VolatilityUsually volatile – data is lost when power is removed (e.g., RAM).Non‑volatile – retains data without power (e.g., HDD, SSD, CD‑ROM).
SpeedVery fast (nanoseconds to microseconds) to match CPU speed.Slower (microseconds to milliseconds) compared with internal memory.
CapacityLimited, typically from a few megabytes to several gigabytes.Large, ranging from tens of gigabytes to several terabytes.
Cost per MegabyteHigher cost.Lower cost.
Typical DevicesRAM modules, cache memory, ROM chips.Hard‑disk drives (HDD), solid‑state drives (SSD), USB flash drives, CDs/D \cdot Ds, magnetic tapes.
Access MethodRandom access – any location can be reached directly.Random access for SSDs and HDDs; sequential access for magnetic tapes.
Role in System OperationFacilitates fast execution of programs and immediate data manipulation.Stores operating system, applications, user files, and backup copies.

How the Two Work Together

  1. When a program is launched, its code is copied from backing storage to internal memory.

  2. The CPU fetches instructions from internal memory, processes data, and may write results back to internal memory.

  3. When the user saves a file, the data is transferred from internal memory to backing storage for permanent keeping.

  4. During power‑off, data remaining only in internal memory (RAM) is lost, while data stored on backing storage remains intact.

Common Misconceptions

  • “RAM is a type of hard drive.” – Incorrect; RAM is volatile primary memory, while hard drives are non‑volatile secondary storage.

  • “All storage devices are equally fast.” – Incorrect; internal memory is orders of magnitude faster than most backing storage devices.

  • “If a file is in the recycle bin, it is stored in RAM.” – Incorrect; the file remains on the backing storage until permanently deleted.

Suggested diagram: Flow of data between backing storage, internal memory, CPU, and input/output devices.

Summary

Internal memory provides the fast, temporary workspace that the CPU needs to execute programs efficiently, while backing storage offers large, permanent space for keeping data and software. Understanding their distinct characteristics—volatility, speed, capacity, cost, and role—helps learners appreciate how computers manage and preserve information.