It is a technique  used in database design  that helps  describe the relationship  between various entities  of an organization.

It contains the day-to-day information generated from business activities. It is used to update or process the master file. For example, addresses of the employees.

It describes how records are stored within a file.

It specifies the properties of relationships. For example, vendor code, student name.

Backup files that contain historical versions of other files.

They contain copies of master and transaction records in order to chronicle any changes that are made to the master file. It facilitates auditing and provides mechanism for recovery in case of system failure

It consists of diagram consisting of rectangular boxes that represent the modules, connecting arrows, or lines.

It helps the administrator to understand the flow of data in the system to correct the flaws and get the system working.

The main module is divided into several smaller and simpler sub modules or segments based on the task performed by each module. Then, each sub module is further subdivided into several sub modules of next lower level This process of dividing each module into several sub modules continues until the lowest level modules, which cannot be further subdivided, are not identified.

It is a data-flow based methodology that helps in identifying the input and output of the developing system.

It describes inputs, outputs, and processing logic for all the program modules.

It serves as the technical specifications for the IS and how the objectives of the IS are accomplished.

It includes instructions and information to the users who will interact with the system.

This process of grouping several simpler modules to form higher level modules continues until the main module of system development process is achieved.