Here, we will see primarily three levels in the data flow diagram, which are: 0-level DFD, 1-level DFD, and 2-level DFD. Levels in DFD are numbered 0, 1, 2 or beyond. Infact, DFDs may be partitioned into levels that represent increasing information flow and functional detail. The DFD may be used to perform a system or software at any level of abstraction. Source or Sink: Source or Sink is an external entity and acts as a source of system inputs or sink of system outputs. The data store can have an element or group of elements. A data store indicates that the data is stored which can be used at a later stage or by the other processes in a different order. Standard symbols for DFDs are derived from the electric circuit diagram analysis and are shown in fig:Ĭircle: A circle (bubble) shows a process that transforms data inputs into data outputs.ĭata Flow: A curved line shows the flow of data into or out of a process or data store.ĭata Store: A set of parallel lines shows a place for the collection of data items. Defer error conditions and error handling until the end of the analysis.
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