There are many functions of general-purpose DBMS software but the main functions are:
(I) Defining the Structure of Database: Which involves defining tables
and their relationships, fields and their data types and constraints for data to be stored in the database.
(ii) Populating the Database: Which involves to store data into database.
(iii) Manipulating the Database: Which involves to retrieve specific data. Update data, delete data, insert new data, and to generate reports.
Now consider the example of university computer file-based processing system , which is converted to database management system , All of the data about applicants, students, courses, and faculty is stored in a single file called database. The data is integrated into database. It means that the data items are stored in a compatible format and logical connection among them is also stored.
The database contains a description of its own structure so that the DBMS "knows" what data items exist and how they are related to each other. Many users can share the database through the DBMS. The DBMS also provides a user-interface for online queries. The users can access the database directly from terminals, using the query language such as SQL statements.