Secondary storage is considered to be any non- volatile storage mechanism…

The idea

Secondary storage is storage that keeps its contents when power is removed (non-volatile) and is not directly addressable by the CPU. Because the CPU cannot reach it directly, data must first be copied into main memory before it can be processed. Typical examples are a hard disk drive, a solid-state drive, a USB flash drive and optical media. A useful test is again two questions: does the contents survive a power loss, and is it outside the CPU's direct access? If both are yes, it is secondary storage.

For example: A saved document lives on an SSD; when opened, a copy is loaded into RAM so the CPU can work on it.

What earns the marks

• Identifies secondary storage as non-volatile, retaining data without power.
• Recognises that secondary storage is not directly accessible by the CPU.
• Gives valid examples such as HDD, SSD, USB flash drive or optical media.
• Explains that data must be copied into main memory before the CPU can use it.
• Distinguishes secondary storage from main memory using the volatility and direct-access tests.

Common mistakes and how to put them right

• Calling RAM secondary storage.

  Put it right: Correct this because RAM is volatile and directly accessible, so it is main memory.

• Assuming secondary storage is directly readable by the CPU.

  Put it right by noting data is first loaded into main memory.

• Forgetting the non-volatile requirement.

  Put it right by checking that contents survive a power loss.

Exam tips

• Apply the two-part test: non-volatile, and not directly accessible by the CPU.
• Give a concrete example such as an SSD or hard disk and say why it fits.
• Contrast with RAM to show you understand volatility and direct access.