hash function

from The Free On-line Dictionary of Computing (8 July 2008)
hash function

   <programming> A {hash coding} {function} which assigns a data
   item distinguished by some "key" into one of a number of
   possible "hash buckets" in a hash table.  The hash function is
   usually combined with another more precise function.

   For example a program might take a string of letters and put
   it in one of twenty six lists depending on its first letter.
   Ideally, a hash function should distribute items evenly
   between the buckets to reduce the number of {hash collisions}.
   If, for example, the strings were names beginning with "Mr.",
   "Miss" or "Mrs." then taking the first letter would be a very
   poor hash function because all names would hash the same.

   (1997-08-03)