問78
頻出度★★☆
データ量の大小関係のうち, 正しいものはどれか。
平成23年度 秋期 ITパスポート試験 問78
テクノロジ系基礎理論 › 情報に関する理論
This question's explanation and your answers so far.
解説
問 78
- ア
正解 The correct answer is ア. The k, M, G, and T attached in front of the byte, which expresses an amount of data (amount of information), are called prefixes, and they indicate a multiplying factor that packs large numbers together. In the decimal definition, k (kilo) is 10^3 = 1,000 times, M (mega) is 10^6 = one million times, G (giga) is 10^9 = one billion times, and T (tera) is 10^12 = one trillion times, so neighbouring prefixes are each 1,000 times apart. In other words, 1 megabyte = 1,000 kilobytes, 1 gigabyte = 1,000 megabytes, and 1 terabyte = 1,000 gigabytes. Note that for computer storage capacity there is also the common practice of matching the binary system and treating k as 2^10 = 1,024, M as 2^20, G as 2^30, and T as 2^40; even then the ratio between neighbouring prefixes stays constant at 1,024, so the size order k < M < G < T itself does not change at all. Therefore, lining them up from the smallest gives 1 kilobyte < 1 megabyte < 1 gigabyte < 1 terabyte, and ア, which is written exactly in this order, is correct. As a memory aid, hold the prefixes as one chain, k → M → G → T, growing by three digits at each step (or by 2^10 at each step in binary).
Incorrectイ
The part up to 1 kilobyte < 1 megabyte is correct, but the 1 terabyte < 1 gigabyte that follows is wrong. T (tera) is 10^12 and G (giga) is 10^9, so the correct relation is 1 gigabyte < 1 terabyte, and 1 terabyte is 1,000 times as large as 1 gigabyte. Because the order of T and G is swapped, the sequence as a whole does not form a correct size relation.
Incorrectウ
The mistake is placing 1 terabyte between 1 kilobyte and 1 megabyte. T (tera) = 10^12 is the largest of the four units that appear in the choices, and it can never be smaller than 1 megabyte (10^6) or 1 gigabyte (10^9). Correctly, T comes last, so this ordering does not hold.
Incorrectエ
The mistake is placing 1 terabyte at the head as if it were the smallest. T (tera) = 10^12 is the largest unit, equal to one billion times k (kilo) = 10^3, so the relation 1 terabyte < 1 kilobyte does not hold. Only the k < M < G part is correct, but because the position of T at the head goes against the order of the prefixes, the sequence is wrong as a whole.
ここがポイント
- The order of the prefixes that express large quantities — k (kilo) = 10^3, M (mega) = 10^6, G (giga) = 10^9, T (tera) = 10^12, growing 1,000 times at each step in the order k → M → G → T. Just remembering this order lets you decide at once that 1 kilobyte < 1 megabyte < 1 gigabyte < 1 terabyte.
- The relation to binary prefixes and the prefixes for small quantities — for storage capacity there is also the practice of taking k = 2^10 = 1,024, M = 2^20, G = 2^30, and T = 2^40, but because the ratio is constant the size order is the same as in the decimal notation. Conversely, the prefixes that express small quantities are m (milli) = 10^-3, μ (micro) = 10^-6, n (nano) = 10^-9, and p (pico) = 10^-12, which are used when comparing processing times and access times.
用語