index file

(data structure)

Definition: A file which stores keys and an index into another file. The index file may have additional structure, e.g., be a B-tree.

See also inverted index, forward index.

Note: An index file is helpful if records are large: the keys and indexes can be extracted, sorted, and the original file accessed faster than the original file could be rearranged into sorted order. Also if the file needs to be accessed by different keys at the same time, it cannot be sorted by all of them. So a index file is maintained for each different key.

Author: PEB

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Entry modified 17 December 2004.
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Cite this as:
Paul E. Black, "index file", in Dictionary of Algorithms and Data Structures [online], Paul E. Black, ed. 17 December 2004. (accessed TODAY) Available from: