The external factors that affect your system are the primary focus of this System Context Diagram and DFD. It's the bare bones of data flow diagrams, showing the relationships between the various parts of the system and any external entities. Because of its simplicity, it’s sometimes called a level 0 data flow diagram. Using the context diagram, you can see all the elements that need to be included in the system and how they interact. You can use this data to figure out how to organize the software as a whole so that it better meets the needs of your customers.
