What is the difference between a data flow diagram and a flow chart

Question

I want to know why we use Data Flow Diagrams instead of flow charts

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The difference between a data flow diagram  DFD  and a flow chart  FC  are that a data flow diagram typically describes the data flow within a system and the flow chart usually describes the detailed logic of a business process

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A flow chart details the processes to follow  A DFD details the flow of data through a system   In a flow chart  the arrows represent transfer of control  not data  between elements and the elements are instructions or decision  or I O  etc    In a DFD  the arrows are actually data transfer between the elements  which are themselves parts of a system    Wikipedia has a good article on DFDs here

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A DFD shows how the data moves through a system  a flowchart is closer to the operations that system does    In the classic make a cup of tea example  a DFD would show where the water  tea  milk  sugar were going  whereas the flowchart shows the process

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Data Flow Diagrams The formal  structured analysis approach employs the data-flow diagram  DFD  to assist in the functional decomposition process  I learned structured analysis techniques from DeMarco  7   and those techniques are representative of present conventions  To summarize  DFD s are comprised of four components

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Although my experience with DFD diagrams is limited I can tell you that a DFD shows you how the data moves  flows  between the various modules  Furthermore a DFD can be partitioned in levels  that is in the Initial Level you see the system  say  a System to Rent a Movie  as a whole  called the Context Level   That level could be broken down into another Level that contains activities  say  rent a movie  return a movie  and how the data flows into those activities  could be a name  number of days  whatever   Now you can make a sublevel for each activity detailing the many tasks or scenarios of those activities  And so on  so forth  Remember that the data is always passing between levels   Now as for the flowchart just remember that a flowchart describes an algorithm

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Data flow diagram shows the flow of data between the different entities and datastores in a system while a flow chart shows the steps involved to carried out a task  In a sense  data flow diagram provides a very high level view of the system  while a flow chart is a lower level view  basically showing the algorithm    Whether you use data flow diagram or flow charts depends on figuring out what is it that you are trying to show

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Other answers have gone over the basics of what each thing is  At the higher level  a flowchart is a design level tool  while DFDs are more analysis   DFDs have some nice features  Since they show the flow of data  some things become more obvious when charted this way  some data is only used by a few routines  some routines use only some bits of data  some routines touch everything  Seeing that up front helps organize  restructuring  and planning   A follow-on worth exploring is the Event-Response Diagram  which is basically a DFD only showing process and data needed to process an  event   meaning something triggered externally  customer makes payment  etc

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Flow chart describes the program  see old fortran flow charts - surely  there are some floating around on google    Data flow diagram determines the flow of data  for example  between subroutines  or between different programs

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Data flow diagram  A modeling notation that represents a functional decomposition of a system   Flow chart  Step by step flow of a programe

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A Data Flow Diagram is functional relationship which includes input values and output values and internal data stored      A Flow Chart is a process relationship which includes input and output values

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Data Flow and Flow Chart differ in processes  flow  and timing    Processes  a   On DFDs  processes can operate in parallel  at-the-same-time    b   On flowcharts  processes execute one at a time       Flow  a   DFDs show the flow of data through a system  b   Flowcharts show the flow of control  sequence and transfer of control       Timing  a   Processes on a DFD can have dramatically different timing  daily  weekly  on demand   b    Processes on flowcharts are part of a single program with consistent timing

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You should use whatever you like  The diagram is just a tool  Use whatever tool fits you and your problem best  I usually just use boxes and arrows and squiggles and circles and little stick figures and whatever else I think gets the point across to the viewer  In short it doesn t matter if you even use a standard diagraming standard  People are usually pretty good at understanding pictures

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Between the above answers its been explained but I will try to expand slightly     The point about the cup of tea is a good one  A flow chart is concerned with the physical aspects of a task and as such is used to represent something as it is currently  This is useful in developing understanding about a situation communication training etc etc  You will likley have come across these in your work places  certainly if they have adopted the ISO9000 standards   A data flow diagram is concerned with the logical aspects of an activity so again the cup of tea analogy is a good one  If you use a data flow diagram in conjunction with a process flow your data flow would only be concerned with the flow of data information regarding a process  to the exclusion of the physical aspects  If you wonder why that would be useful then its because data flow diagrams allow us to move from the  as it is  situation and see it that something as it could will be  These two modelling approaches are common in structured analysis and design and typically used by systems business analysts as part of business process improvement re-engineering

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have a look to this site   http   yourdon com strucanalysis wiki index php title Chapter 9 The Flow   its really help u to understand what is DFD

[flowchart] What is the difference between a data flow diagram and a flow chart?

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