Know and understand differences between backing storage and internal memory

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

Aspect	Internal Memory	Backing Storage
Purpose	Temporarily holds data and instructions that the CPU is currently processing.	Provides long‑term, permanent storage of programs, files, and system data.
Volatility	Usually volatile – data is lost when power is removed (e.g., RAM).	Non‑volatile – retains data without power (e.g., HDD, SSD, CD‑ROM).
Speed	Very fast (nanoseconds to microseconds) to match CPU speed.	Slower (microseconds to milliseconds) compared with internal memory.
Capacity	Limited, typically from a few megabytes to several gigabytes.	Large, ranging from tens of gigabytes to several terabytes.
Cost per Megabyte	Higher cost.	Lower cost.
Typical Devices	RAM modules, cache memory, ROM chips.	Hard‑disk drives (HDD), solid‑state drives (SSD), USB flash drives, CDs/D \cdot Ds, magnetic tapes.
Access Method	Random access – any location can be reached directly.	Random access for SSDs and HDDs; sequential access for magnetic tapes.
Role in System Operation	Facilitates 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.

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.