In computer science, a lookup table is a data structure, usually an array or associative array, often used to replace a runtime computation with a simpler array indexing operation. The savings in terms of processing time can be significant, since retrieving a value from memory is often faster than undergoing an 'expensive' computation or input/output operation. The tables may be precalculated and stored in static program storage, calculated (or "pre-fetched") as part of a programs initialization phase (memoization), or even stored in hardware in application-specific platforms. Lookup tables are also used extensively to validate input values by matching against a list of valid (or invalid) items in an array and, in some programming languages, may include pointer functions (or offsets to labels) to process the matching input.
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Famous quotes containing the word table:
“Life is a thin narrowness of taken-for-granted, a plank over a canyon in a fog. There is something under our feet, the taken-for-granted. A table is a table, food is food, we are we—because we don’t question these things. And science is the enemy because it is the questioner. Faith saves our souls alive by giving us a universe of the taken-for-granted.”
—Rose Wilder Lane (1886–1968)