We have mostly illustrated storage and retrieval with simple entities such
as ints or strings. Then the value of an object and its unique identifier
are one and the same. But in practice what is stored and retrieved
are objects such as personnel records, descriptions of regions in
space, items for sale in a catalog, forms defining a sale from a
catalog, dictionaries, etc. We typically use some subset of the values
Key - A value or values (an object type) which can be used to locate the storage
location of another object or collection of values.
1. The unique identifier of an object may be used as its key or
a key may be derived from the unique identifier.
2. We speak of “searching for a key.” to find the location of the object
3. But the index of a location in an array or vector is a location which
What do we store and retrieve?