問76
頻出度★★☆
メモリに関する説明のうち, 適切なものはどれか。
平成30年度 春期 ITパスポート試験 問76
テクノロジ系コンピュータ構成要素 › メモリ
This question's explanation and your answers so far.
解説
問 76
- ア
正解 “ア” is correct. DRAM (Dynamic RAM) stores information by holding an electric charge in a capacitor. Because the charge gradually leaks away over time and the contents are lost, it needs a periodic read-and-write-back cycle called a “refresh (rewrite)”. Its structure is simple and the circuit per bit is small, so it is easy to make cheaply and in large capacity, and it is therefore widely used as the main memory of PCs and similar devices. The statement “needs to be periodically rewritten, and is mainly used as main memory” correctly describes the characteristics of DRAM.
Incorrectイ
ROM (Read Only Memory) is non-volatile and is mainly used for reading out programs and fixed data; it is not used as cache memory. What is used for cache memory is SRAM, which has a very fast access speed. The claim that “ROM has a fast access speed and is used for cache” is incorrect.
Incorrectウ
SRAM (Static RAM) is a high-speed memory that stores data using flip-flop circuits, but it is a “volatile” memory whose contents disappear when the power is turned off, and it is mainly used as cache memory. What is used as USB memory is “non-volatile” flash memory, which keeps its contents even when the power is off. The claim that “SRAM is non-volatile and is used as USB memory” is incorrect.
Incorrectエ
The description “programs and data are written in at the time of manufacture, and users cannot change the contents” is that of a mask ROM. Flash memory is a non-volatile memory whose data can be electrically written and erased (rewritten), and it is used in USB memory, SSDs, SD cards, and the like. As an explanation of flash memory, it is incorrect.
ここがポイント
- Classification of semiconductor memory: RAM is volatile (contents are lost when the power is off), while ROM and flash memory are non-volatile. Among RAM, DRAM needs refreshing and, being cheap and high-capacity, is used as main memory, whereas SRAM is fast and is used as cache memory.
- Flash memory is an electrically rewritable non-volatile memory used in USB memory, SSDs, and so on. Distinguish it from a mask ROM, which is fixed at the time of manufacture and cannot be changed.
用語