問58
頻出度★★☆
媒体①～⑤のうち，不揮発性の記憶媒体だけを全て挙げたものはどれか。 ① DRAM ② DVD ③ SRAM ④ 磁気ディスク ⑤ フラッシュメモリ
平成24年度 秋期 ITパスポート試験 問58
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 58
Incorrectア
①, ②. ② DVD is indeed non-volatile, so that item is fine, but ① DRAM is volatile memory whose contents disappear when the power is cut, so it must not be mixed in. In addition, ④ magnetic disk and ⑤ flash memory, which are also non-volatile, are missing, so this option fails the all-and-only condition in two ways.
Incorrectイ
①, ③, ⑤. ⑤ Flash memory is correctly non-volatile, but both ① DRAM and ③ SRAM lose their contents when the power is cut; they are volatile memory and cannot be included in a list of non-volatile media. The difference between DRAM and SRAM is whether a refresh operation is required (DRAM requires it, SRAM does not), not a difference between volatile and non-volatile, and that is the trap set here.
- ウ
正解 Non-volatile means the property that the stored contents are retained even when the power supply stops. Checking ①–⑤ one by one: ② DVD is an optical disc that records data as changes in light reflectance; ④ magnetic disk (such as a hard disk) records data as the direction of magnetization of a magnetic material; ⑤ flash memory is a semiconductor memory that holds electric charge trapped in a region surrounded by an insulating film. All of them keep their data even after the power is turned off, so they are non-volatile storage media. On the other hand, ① DRAM and ③ SRAM lose their contents when the power is cut, so they are volatile memory. The non-volatile media are therefore the three items ②, ④ and ⑤, and the option that lists exactly these, with nothing extra and nothing missing, is ウ. The question asks for the option that lists all and only the non-volatile media, so you must neither mix in a volatile one nor leave out a non-volatile one.
Incorrectエ
④, ⑤. Both ④ magnetic disk and ⑤ flash memory are non-volatile, so the items listed are correct in themselves, but ② DVD, which is also non-volatile, is left out. The question requires listing all of the non-volatile media, so an option that picks only some of the correct items does not satisfy the condition.
ここがポイント
- Distinguish volatile (contents disappear when the power is cut) from non-volatile (contents remain even after the power is cut). Typical volatile devices are the semiconductor memories used as main memory, such as DRAM and SRAM; typical non-volatile ones are magnetic disks, optical discs (CD/DVD/BD), flash memory (SSD, USB memory, SD card) and ROM.
- How to solve combination questions of the all-and-only type. Before looking at the options, judge ①–⑤ one by one as correct or incorrect, then choose the option that exactly matches your judgement. Check both that no wrong item has been mixed in (inclusion error) and that no correct item has been left out (omission error).
用語