We have previously looked at arrays and lists, where items are stored in sequence and accessed by index number. Index numbers work well for computers. They are integers so they are fast and easy to manipulate. However, they don't always work so well for us. For example, if we have an address book entry, let's say at index number 56, that number doesn't tell us much. There is nothing to link a particular contact with number 56. It is difficult to retrieve an entry from the list using the index value.
In this chapter, we are going to look at a data structure that is better suited to this kind of problem: a dictionary. A dictionary uses a keyword instead of an index number, and it stores data in (key, value) pairs. So, if that contact was called James, we would probably use the keyword James to locate the contact. That is, instead of accessing...