Four elements of data flow diagram

The four elements of the data flow diagram are:

1. External entities, people or transactions outside the system and related to the system, which express the external aspects of the system data Source and destination;

2. Data processing, the logical processing capability of data, that is, the exchange function of data;

3. Data storage, a general term for the logic after certain data is saved, It does not refer to the physical location and physical medium where the data is stored;

4. Data flow, the input or output of the processing function (the arrow indicates the direction of data flow).

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