The purpose of a DFD is to show the scope and boundaries of a system as a whole.
It shows how information enters and leaves the system, what changes the information and where information is stored. It can be manual, automated, or a combination of both. A neat and clear DFD can depict a good amount of the system requirements graphically.
A Data Flow Diagram (DFD) is a traditional way to visualize the information flows within a system.
