A cache is a structure that contains a copy of information that originates at some source. Generally speaking, a cache consists of a table of key/value pairs. For each pair, a key represents a question and the corresponding value represents an answer.
|Santa Clara||Santa Clara|
|Palo Alto||Santa Clara|
|Marina del Rey||Los Angeles|
For example, to look up the California county that contains the city of Marina del Rey, we ask a question—What county is Marina del Rey located in?—and obtain an answer—Los Angeles. Table 4-1 shows this information in a sample cache of cities and counties.
The keys and values in a cache ...