The DFD

this presentationb help to learn what is dfd to easily

1. The DFD Presented By Akshay Modak ,Arijit Sadhukhan, Biswarup Mondal,Yubraj mallick

2. Contents What is DFD History of DFD Difference between DFD & Flowchart Types of DFD DFD symbols LEVEL 0 DFD LEVEL 1 DFD LEVEL 2 DFD Uses of DFD About DFD Conclusion

3. What is DFD A   Data F low Diagram  ( DFD ) is a graphical representation of the "flow" of data through an  information System.   DFD is can also be used for the visualization of Data processing(Structured program)

4. History In the 1970’s,  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

5. Difference between DFD & Flowchart DFD Flowchart Data flow diagram presents the flow of data Data flow diagram define the functionality of a system Data flow diagram are used to describe the path of data that will complete that process Flow chart presents steps to complete a process Flowchart shows how to make a system function Flowchart are used in designing a process

6. Types of DFD Data flow diagrams(DFD)are categorized as either logical or physical. 1). LOGICAL DFD :- A logical DFD focuses on the business and how the business operates. It describes the business events that take place and the data required and produced by each event. 2). PHYSICAL DFD :- A physical DFD shows how the system will be implemented.

7. Difference Between Physical and Logical DFD Physical DFD Logical DFD It is describe h0w the process will be implemented. It represent Program modules and manual procedures. The data stores in physical file database and manual files. It represent how the business operator. It represent the business activities. The data store represent the collection of data regardless the data store.

8. DFD symbols

9. The Process.. The process is the manipulation or work that transforms data, performing computations, making decisions (logic flow),or directing data flows based on business rules, In other words, a process receives input and Generates.

10. The Data flow.. Data flow is the movement of data between the external entity, the process, and the data store. Data flow portrays the interface between the components of the DFD.

11. The Data store.. A data store is where a process stores data between processes for later retrieval by that same process or another one.

12. The External Entity.. An entity is the source or destination of data. The source in a DFD represents these entities that are outside the context of the system.

13. LEVEL 0 DFD Rules of Level 0 DFD:- Definition:- Data stores NOT shown.They are within the system. one process represent the entire system. Data arrows show input and output. A context diagram is a top  level  (also known as " Level 0 ")  data flow diagram . It only contains one process node ("Process  ") that generalizes the function of the entire system in relationship to external entities.  DFD  Layers.

14. LEVEL 1 DFD Definition :- Rules of Level 1 DFD:- 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. Level 1 DFD must balance with the context diagram it describes. Input going into a process are different from outputs leaving the process. Data stores are first shown at this level.

15. LEVEL 2 DFD Definition:- Rules of level 2 DFD:- A  level 2 data flow diagram  ( DFD ) offers a more detailed look at the processes that make up an information system than a  level  1  DFD  does. It can be used to plan or record the specific makeup of a system. ... You can then input the particulars of your own system. Level 2 DFD must balance with the Level 0 it describes. input going into a process are different from output leaving the process. Continue to show data stores.

16. Use of DFD

17. About DFD Advantages…. Disadvantages…. It aids in describing the boundaries of the system . It is used as the part of system documentation file . It supports the logic behind the data flow within the system. Physical considerations are left out . It make the programmers little confusing concerning the system . DFDs take a long time to create, which may not be feasible for practical purposes.

18. Conclusion Data flow analysis has proved itself to be an essential technique in the grand scheme of developing custom software solutions. It greatly improves conceptual clarity, for both the developer and the client. It helps show the true scope of the project, which is almost always bigger than originally anticipated.

19. Refference www.google.co.in www.wikipedia.org www.lucidchart.com/pages/data-flow-diagram