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A data flow diagram (DFD) shows how data moves through a system: the processes that transform it, the external entities that send and receive it, the stores where it sits, and the flows between them. This template is a worked retail checkout example, with numbered processes, data stores, labeled flows, and a legend for the four symbols. Analysts and developers use it to map a system's data before building or documenting it.
A data flow diagram and a flowchart answer different questions. A DFD shows what data moves and where it goes: the processes that transform it, the stores that hold it, and the flows between them, with no concern for order or timing. A flowchart shows control flow: the sequence of steps and decisions, in the order they happen. Use a DFD to map a system's data; use a flowchart to map a procedure's logic. Many systems get documented with both.
A data flow diagram, or DFD, is a visual map of how data moves through a system. It uses four elements: processes that transform data, external entities that send or receive it, data stores that hold it, and data flows, the labeled arrows between them. A DFD shows what happens to data, not the order steps run in, which makes it a clear way to model and document a system.
A DFD has four symbols: a process (a circle in Yourdon and Coad notation, a rounded rectangle in Gane and Sarson), an external entity (a square or rectangle at the boundary), a data store (an open-ended rectangle or parallel lines), and a data flow (a labeled arrow). This template uses one consistent set and includes a legend, so every shape on the board has a clear meaning.
DFDs are drawn in levels. Level 0, the context diagram, shows the whole system as a single process with its external entities. Level 1 breaks that process into the main functions, numbered 1.0, 2.0, and so on. Level 2 explodes a single level 1 process into more detail. You go only as deep as the system needs, which keeps each diagram readable.
This template's board is one: a retail checkout. The Customer sends items and a barcode to a Scan & Ring Up process, which reads the Product Catalog store and passes an amount due to Process Payment. That talks to a Card Payment Processor, records a sale, decrements the Inventory store, and a Generate Reports process sends a sales and inventory report to the Store Manager.
A DFD shows what data moves and where it goes: processes, stores, and the flows between them, with no concern for order or timing. A flowchart shows control flow: the sequence of steps and decisions, in the order they happen. Use a DFD to map a system's data, and a flowchart to map a procedure's logic. They often describe the same system from two different angles.