Evolution of DBMS

In the early days of computing, disk storage was extremely expensive.  Most application systems ran in batch mode using data that was stored on magnetic tape.

Data had to be read sequentially from flat files.  For performance reasons, the management of data was tightly integrated with the application system.

As the cost of disk storage fell, opportunities to store data for real-time access arose.

Specialized DBMS software emerged during the 1960s for the sole purpose of managing data.  Application systems were then able to focus on the user interface, screen navigation, data validations etc. and could leave the data management tasks to the specialized DBMS technology.

The application system simply had to call the DBMS when it needed to read or store data.

The early DBMS systems required that data be structured if a manner that was conducive to how it would be stored and/or accessed.  Data was stored in database records that were linked to related data via "pointers". (i.e. hierarchical and network databases).

Although speed of access was good, flexible access to data was not.

As the cost of data storage fell, it became feasible to store data in tables.  This eliminated much data redundancy and provided much more flexible data access.  Most DBMS databases today are relational.