Software Design Center

HOW TO DRAW DATA FLOW DIAGRAMS


What are Data Flow Diagrams?
Data flow diagrams illustrate how data is processed by a system in terms of inputs and outputs.

A data flow diagram
A data flow diagram


Data Flow Diagram Notations
You can use two different types of notations on your data flow diagrams: Yourdon & Coad or Gane & Sarson.


Process Notations
Yourdon and Coad Process Notations
Yourdon and Coad
Process Notations


Process
Gane and Sarson
Process Notation

Process
A process transforms incoming data flow into outgoing data flow.
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Datastore Notations
Datastore Notations
Yourdon and Coad
Datastore Notations


DataStore
Number DataStore
Gane and Sarson
Datastore Notations

DataStore
Datastores are repositories of data in the system. They are sometimes also referred to as files.
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Dataflow Notations
Dataflow Notations

Dataflow
Dataflows are pipelines through which packets of information flow. Label the arrows with the name of the data that moves through it.
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External Entity Notations
External Entity Notations

External Entity
External entities are objects outside the system, with which the system communicates. External entities are sources and destinations of the system's inputs and outputs.
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