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:
“How to attain sufficient clarity of thought to meet the terrifying issues now facing us, before it is too late, is ... important. Of one thing I feel reasonably sure: we can’t stop to discuss whether the table has or hasn’t legs when the house is burning down over our heads. Nor do the classics per se seem to furnish the kind of education which fits people to cope with a fast-changing civilization.”
—Mary Barnett Gilson (1877–?)