Three types of DFD are context, diagram0, detailed dataflow diagrams.
Context DFD: The emphasis is on the relationship between the system and its environment the system as a whole is represented by a bubble, and the external entities are shown as squares from which input flows and to which output is directed. No information about the structure of the system itself is pictured in a context DFD.
Diagram 0: A diagram 0 is a diagram showing the system itself. It pictures the major processes along with the external entities, data stores and data flow. It is a single ,top-level diagram of the system, and does not describe each process in detail. Parts of the diagram can be expended or exploded using more detail sub diagrams.
Detailed DFD: Detailed DFD are explosions of higher level presentations and are detailed pictures of major processes or subsystems. They are likely to be used by designers in their own work rather than for presentations to users or managers. If more detail is needed each of the processes can be further exploded using a still more detail diagram. For example if we wish to expand the "Check Class counts" process, we would construct a diagram called detail DFD.
Context DFD: The emphasis is on the relationship between the system and its environment the system as a whole is represented by a bubble, and the external entities are shown as squares from which input flows and to which output is directed. No information about the structure of the system itself is pictured in a context DFD.
Diagram 0: A diagram 0 is a diagram showing the system itself. It pictures the major processes along with the external entities, data stores and data flow. It is a single ,top-level diagram of the system, and does not describe each process in detail. Parts of the diagram can be expended or exploded using more detail sub diagrams.
Detailed DFD: Detailed DFD are explosions of higher level presentations and are detailed pictures of major processes or subsystems. They are likely to be used by designers in their own work rather than for presentations to users or managers. If more detail is needed each of the processes can be further exploded using a still more detail diagram. For example if we wish to expand the "Check Class counts" process, we would construct a diagram called detail DFD.