The authors are in an age repeatedly referred to the information age. Information is gathered almost everywhere in the users' everyday lives. The amount of information stored in modern databases makes manual analysis intractable. Data mining provides tools to reveal previously unknown information in large databases. A number of algorithms have been proposed to determine frequent pattern. Apriori algorithm is the first algorithm proposed in this field. With the time a number of changes proposed in Apriori to enhance the performance in term of time and number of database passes.