Sequential files. Unordered sequential files. Ordered sequential files. External sorting. Heap sort. Replacement selection sort. Large memory sorting. B+tree index. Hashing. Classical hashing. Linear hashing. Introduction to DBMSs. Relational databases. Relational query languages. Relational algebra. Relational calculus. SQL. QBE.QUEL. Implementing the join operation. Entity-Relationship data model.