Which statement best describes primary storage?

• A. Primary storage is non-volatile external storage.
• B. Primary storage is external cloud storage.
• C. Primary storage consists of cache memory only.
• D. Primary storage is volatile memory such as RAM and cache.

Answer: (D)

Primary storage is the memory the processor can access directly to run programs and hold data that is actively being used. It is volatile, meaning its contents disappear when power is lost. The fastest portion is cache, located close to the CPU, and the larger, still-volatile portion is RAM, the main memory. Together, RAM and cache constitute primary storage because they’re the immediate workspace for the CPU. In contrast, non-volatile external storage like hard drives, SSDs, or cloud storage preserves data without power but is much slower and not directly used for running programs, so those are examples of secondary storage. Saying primary storage is only cache memory is too narrow, and describing it as non-volatile external storage or external cloud storage misses the key point that primary storage is the volatile, directly accessible workspace of the CPU.