Mask ROM fundamentals – programmability Which statement best describes a mask ROM (Read-Only Memory) device?

Introduction / Context:
ROM variants differ by how and when their contents are defined. Mask ROM is one of the earliest and most cost-effective approaches for high-volume, unchanging firmware.

Given Data / Assumptions:

• Mask ROM contents are fixed by a photomask during wafer fabrication.
• No field-programmability is provided.
• Nonvolatile retention is expected.

Concept / Approach:
Because data is encoded at the silicon level, mask ROM offers low unit cost at volume but zero flexibility after production. It is ideal for stable products but unsuitable for frequent updates.

Step-by-Step Solution:
Establish programmability: fixed at manufacture.Determine volatility: nonvolatile by definition.Conclude: “permanently programmed during manufacturing” is correct.

Verification / Alternative check:
Standard memory taxonomy lists mask ROM as factory-programmed, contrasted with EPROM/EEPROM/flash which are field-programmable.

Why Other Options Are Wrong:
Volatile is false; ROM retains data without power.Mask ROM is not reprogrammable; UV erasure applies to EPROM, not mask ROM.“Extremely expensive” is context dependent; at high volume it is cheaper per unit than field-programmable options.

Common Pitfalls:
Assuming all ROMs are field-programmable; confusing mask ROM with PROM/EPROM.

Final Answer:
permanently programmed during the manufacturing process