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In computer science, * space refers to the data storage consumed in performing a given task, whether primary (e.g., in RAM) or secondary (e.g., on a hard disk drive) * time refers to that consumed in performing a given task, whether particularly in computation or in general response time. A space-time or time-memory tradeoff is therefore a case where an algorithm or program trades increased space for decreased time. The utility of a given space-time tradeoff is affected by related fixed and variable costs (of, e.g., CPU speed, RAM space, hard-drive space), and is subject to diminishing returns. ==History== Biological usage of time–memory tradeoffs can be seen in the earlier stages of animal behavior. Using stored knowledge or encoding stimuli reactions as "instincts" in the DNA avoids the need for "calculation" in time-critical situations. More specific to computers, look-up tables have been implemented since the very earliest operating systems. In 1980 Martin Hellman first proposed using a time–memory tradeoff for cryptanalysis. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Space–time tradeoff」の詳細全文を読む スポンサード リンク
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