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Index mapping
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<p>Index mapping (or direct addressing, or a trivial <a href="/facts/Hash_function/rk6MlCt3">hash function</a>) in <a href="/facts/Computer_science/lN3pEyPz">computer science</a> describes using an <a href="/facts/Array_data_structure/BKGvF8AM">array</a>, in which each position corresponds to a key in the <a href="/facts/Universe_(mathematics)/v2oJnu4e">universe</a> of possible values. The technique is most effective when the universe of keys is reasonably small, such that <a href="/facts/Memory_allocation/vthLkUpz">allocating</a> an array with one position for every possible key is affordable. Its effectiveness comes from the fact that an arbitrary position in an array can be examined in <a href="/facts/Time_complexity/77T62gmf">constant time</a>. </p>