<P> A DFD shows what kind of information will be input to and output from the system, how the data will advance through the system, and where the data will be stored . It does not show information about process timing or whether processes will operate in sequence or in parallel, unlike a traditional structured flowchart which focuses on control flow, or a UML activity workflow diagram, which presents both control and data flows as a unified model . </P> <P> In the 1970s, Larry Constantine, the original developer of structured design, proposed data flow diagrams as a practical technique based on Martin and Estrin's "Data Flow Graph" model of computation . </P> <P> Data flow diagrams (DFD) quickly became a popular way to visualize the major steps and data involved in software system processes . DFDs were usually used to show data flow in a computer system, although they could in theory be applied to business process modeling . DFDs were useful to document the major data flows or to explore a new high - level design in terms of data flow . </P> <P> Data flow diagrams are also known as bubble charts . DFD is a designing tool used in the top - down approach to Systems Design . This context - level DFD is next "exploded", to produce a Level 1 DFD that shows some of the detail of the system being modeled . The Level 1 DFD shows how the system is divided into sub-systems (processes), each of which deals with one or more of the data flows to or from an external agent, and which together provide all of the functionality of the system as a whole . It also identifies internal data stores that must be present in order for the system to do its job, and shows the flow of data between the various parts of the system . </P>

What is dfd in system analysis and design