Memory taxonomy – persistence of stored data Why are ROM devices classified as nonvolatile memory in digital systems?

Introduction / Context:
Computer memories are often grouped by volatility. Volatile memories require continuous power to retain stored information, while nonvolatile memories retain data without power. This classification is fundamental when selecting storage for firmware versus working RAM.

Given Data / Assumptions:

• The device under discussion is ROM (Read-Only Memory) in its broad sense (mask ROM, EPROM, EEPROM, Flash used as ROM).
• We compare behavior with and without system power.

Concept / Approach:
Nonvolatile memory retains its state without external power. ROMs store firmware or constant data that must persist across power cycles. In contrast, volatile memory like DRAM and SRAM lose their contents when power is removed (DRAM also needs refresh even when powered).

Step-by-Step Solution:

Verification / Alternative check:
System boot sequences depend on code stored in ROM/Flash. If ROM were volatile, systems could not start without external reprogramming every power-up, which contradicts real-world behavior.

Why Other Options Are Wrong:

• They lose memory when power is removed: This describes volatile RAM, not ROM.
• Blank options do not provide a technical statement and can be ignored.

Common Pitfalls:

• Confusing “read-only” with “nonvolatile.” Read-only refers to typical use-mode; many ROM technologies can be rewritten under specific procedures, yet they are still nonvolatile.

Final Answer:
They do not lose memory when power is removed.