hashing and symbol tables we have previously looked at listswhere 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 howeverthey don' always work so well for us if we have an address book entryfor examplewith index number that number doesn' tell us much there is nothing to link particular contact with number it just happens to be the next available position in the list in this we are going to look at similar structurea dictionary dictionary uses keyword instead of an index number soif that contact was called jameswe would probably use the keyword james to locate the contact that isinstead of accessing the contact by calling contacts [ ]we would use contacts ["james"dictionaries are often built using hash tables as the name suggestshash tables rely on concept called hashing that is where we are going to begin our discussion we will cover the following topics in this hashing hash tables different functions with elements hashing hashing is the concept of converting data of arbitrary size into data of fixed size little bit more specificallywe are going to use this to turn strings (or possibly other data typesinto integers this possibly sounds more complex than it is so let' look at an example we want to hash the expression hello worldthat iswe want to get numeric value that we could say represents the string