問65
頻出度★★☆
CD-Rの記録層にデータを書き込むために用いるものはどれか。
平成26年度 秋期 ITパスポート試験 問65
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This question's explanation and your answers so far.
解説
問 65
Incorrectア
There is no method that uses sound to record on a CD-R. Because CDs became widespread for recording music (audio), this choice is confusing, but what is recorded is data obtained by digitizing sound; the writing method itself is not sound waves but a laser beam. There is no common auxiliary storage device that uses sound waves to write to a recording medium.
Incorrectイ
Magnetism is used by magnetic storage media such as hard disks, floppy disks, and magnetic tape, which represent data by the direction of magnetization of a magnetic material. The recording layer of a CD-R is an organic dye, not a magnetic material, so it cannot be written by magnetism. Note also that MO (magneto-optical disc), which uses both light and magnetism, is a medium different from CD-R.
Incorrectウ
Electricity (accumulation of electric charge) is used by flash memory such as SSDs, USB flash drives, and SD cards, which record data by moving charge into and out of semiconductor cells. A CD-R has no electrical contacts on the medium and only exchanges laser light with the drive without contact, so data is not written to its recording layer by electricity.
- エ
正解 The correct answer is エ (Light). A CD-R is an optical disc (optical medium) in the CD family, and its recording layer is coated with an organic dye. When writing, the drive focuses its laser beam on a tiny spot of the recording layer, and the heat alters the dye to create an area of low reflectivity. This corresponds to a pit on a CD-ROM; when reading, a weaker laser beam is applied and the data is restored by detecting the strength of the reflected light. Both writing and reading are done with a laser beam without touching the medium, which is the principle of optical discs, so what is used to write to the recording layer is light.
ここがポイント
- Storage media can be classified by their recording principle: light (optical discs such as CD/DVD/BD), magnetism (HDDs, magnetic tape), electricity = charge (flash memory such as SSDs and USB flash drives), and light + magnetism (MO).
- A CD-R is a write-once (Recordable) optical disc: the heat of a laser beam alters the organic dye in the recording layer, so it can be written only once and cannot be rewritten afterwards. The rewritable CD-RW uses a phase-change material, but it too is an optical disc recorded with a laser beam.
用語