Data Flow diagrams & systems flowcharts

Once the systems analysts have completed their investigation they produce a detailed description of how the existing system works.

Methods used to help describe the system include data flow diagrams and systems flowcharts

Symbols used in DFDs

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External entity (symbol1 - top)– data source or data destination, for example people who generate data such as a customer order, or receive information such as an invoice.

Process (symbol2) – an operation performed on the data. The two lines are optional; the top section of the box can be used to label the process, the middle to give a brief explanation, the bottom to say where the process takes place.

Data store (symbol3) – such as a file held on disk or a batch of documents

Data flow (symbol4 - bottom) – the arrow represents movement between entities, processes or data stores. The arrow should be labelled to describe what data is involved.

Data flow diagram for a theatre booking system.

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The symbols used in flowcharts

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A systems flowchart

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