Which of the memories must be refreshed many times per second?

Memory chips store data as tiny electrical charges. Some types of memory hold their charge stably once set, while others leak charge over time and must be rewritten repeatedly to keep the stored data intact.

Dynamic RAM (DRAM) stores each bit using a capacitor, which naturally loses its charge within a very short time. To prevent data loss, the memory controller must refresh, meaning rewrite, every stored bit many times per second. Static RAM does not need this constant refreshing because it stores each bit using a flip-flop circuit that holds its state as long as power is supplied, which is why static RAM is faster but more expensive per bit. ROM and EPROM store data in a way that does not require power or refreshing to be retained, since they are designed for long-term or permanent storage.

Exam takeaway: link the word dynamic to the need for continuous refreshing, since the capacitor-based storage in dynamic RAM depends on frequent rewriting to avoid losing its data.