Difference between Data flow diagram and block diagram

block diagram dataflow-diagram
Muhammad Burhan picture Muhammad Burhan · Oct 28, 2014 · Viewed 15.6k times · Source

Can anyone explain the difference between Data Flow Diagram and Block Diagram ? I Googled it but didn't get any satisfactory stuff that's why I turned to Stack Overflow.

Thanks.

Answer

darlinton picture darlinton · Oct 28, 2014

It is all about the definition. Data Flow Diagram (DFD) has a very well defined notation and semantic. In the other hand, any diagram made from blocks can be called Block Diagram. You can call a DFD as Block Diagram, but not otherwise. Every time you use a block diagram, you have to specify what each block means, but when you use a square in a DFD, following the Yourdon/DeMarco notation, it means an input/output and so on.

Here it goes an expanded answer, copying from wikipedia:

  • A data flow diagram (DFD) is a graphical representation of the "flow" of data through an information system, modeling its process aspects. A DFD is often used as a preliminary step to create an overview of the system, which can later be elaborated.2 DFDs can also be used for the visualization of data processing (structured design).

  • Block diagram is a diagram of a system in which the principal parts or functions are represented by blocks connected by lines that show the relationships of the blocks.1 They are heavily used in the engineering world in hardware design, electronic design, software design, and process flow diagrams.

  • An interesting note about block diagrams: Because block diagrams are a visual language for describing actions in a complex system, it is possible to formalize them into a specialized programmable logic controller (PLC) programming language. An example is the Function block diagram, one of five programming languages defined in part 3 of the IEC 61131 (see IEC 61131-3) standard.

If you go deeper looking for differences, you need to defined an analytical background. An analogy would be try to find differences between apples and bananas; they are fruits and taste good (at least to me), but they have different shapes and composition. You can establish the differences between fruits if you describe shape, color, vitamins. What are the features you are interested at evaluating DFD and Block Diagrams to tell them apart?

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