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Communications of the ACM

Communications of the ACM

Information Retrieval: PEEKABIT, computer offspring of punched card PEEKABOO, for natural language searching

The “peekaboo” idea from punched card information retrieval methods has been mated with the idea of superimposed punching to produce a programming technique which cuts computer run time in half on a test search of 33,000 subject index entries. A search program using the device has been operational since late 1963. As an item is entered in the store, an 18-byte mask is created from the item's meaningful words using the inclusive OR operation. If, at search time, the logical product (using the AND operation) of this mask and a similarly constructed question mask is not equal to the question mask, then one or more question words are not present in the store item. An equality is inconclusive; the words of the store item must be unpacked and compared with question words. The present store is made up of over 600,000 subject index entries estimated to average 60 characters each. Longer texts, such as abstracts, could be handled by multiple masks.

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