hash tables introduction to hashing in this section we'll introduce hash tables and hashing one important concept is how range of key values is transformed into range of array index values in hash table this is accomplished with hash function howeverfor certain kinds of keysno hash function is necessarythe key values can be used directly as array indices we'll look at this simpler situation first and then go on to show how hash functions can be used when keys aren' distributed in such an orderly fashion employee numbers as keys suppose you're writing program to access employee records for small company withsay , employees each employee record requires , bytes of storage thusyou can store the entire database in only megabytewhich will easily fit in your computer' memory the company' personnel director has specified that she wants the fastest possible access to any individual record alsoevery employee has been given number from (for the founderto , (for the most recently hired workerthese employee numbers can be used as keys to access the recordsin fact access by other keys is deemed unnecessary employees are seldom laid offbut even when they aretheir records remain in the database for reference (concerning retirement benefits and so onwhat sort of data structure should you use in this situationindex numbers as keys one possibility is simple array each employee record occupies one cell of the arrayand the index number of the cell is the employee number for that record this type of array is shown in figure array longsmithnorman ceo , , vegateresa vp , alcazarherman technician , vossheinrich salesman index numbers same as employee numbers figure employee numbers as array indices