Data Flow Diagrams (DFDs) visually represent the flow of data in an information system, outlining inputs, outputs, sources, and destinations of information. Key components include external entities, processes that transform input data, data flows that transmit data, and data stores where data is held. DFDs are beneficial due to their simplicity, making them an effective tool for communicating system functions and logic.

1. Data Flow Diagrams
Prepared by: SARFARAZ

2. What are DFDs?
 A data flow diagrams (dfds) is a graphical representation of the
Flow of data through an information system.
 Dfd is often used to create an overview of the system.
 A Dfd shows what kind of information will be input to and output
from the system, where the data will come from and go to, and
where the data will be stored.
 It does not shows information about the timing of process or
information about whether processes will operate in sequence or in
parallel

3. How does DFDs looks like?
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4. Elements of DFDs
External Entities:
 External entities define the sources and destination of
information entering and leaving the system.
 An external entity can be a person, system, or organization
that has pre-defined behaviour.
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5. Processes:
 A data process transforms input data into output data.
 Data process act directly on data, either from flows or
stores.
 They represent the functionality of the system.
 A process name and number must be unique.
 A process can only exist once on a data flow diagram of
level 0.
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Elements of DFDs

6. Data Flows:
 Data flows are the pipelines through which the data are
transmitted between two components on dfd.
 Flows of data between:
external entities and processes
processes and other processes
processes and data stores
 Can be simple data elements or complex data structures
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Elements of DFDs

7. Data Stores:
 Represent the places where data is stored
 Typically files or database tables
 A manual system can represent physical data stores,
like card indexes or filing systems
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Elements of DFDs

8. Example of DFD

9. Advantages of DFDs
 It is simple graphical technique which is easy to
understand.
 It is useful for communicating current system knowledge to
the user.
 It explains the logic behind the flow within the system.