Atif Dahar

2. •Data flow diagram become popular
in 1970s in software development.

4. Symbols of data flow diagram.
There are four symbols of data flow diagram.
1. Process Notation
2. Data store Notation
3. Data flow Notation
4. External entity Notation

5. Process Notation
• A process transforms incoming data flow into outgoing data flow
Process

6. • Data store are repositories of data in the system. They
are sometimes also referred to as files.
Data store

7. • Data flows are pipelines through which packets of
information flow. Label the arrows with the name of the data
that moves through it.
Data flow

8. • 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.
External entity
External entity

9. Example: this diagram represents a banking
process which maintains customer accounts.
• In this example customers can withdraw or deposit
cash, request information about their account or
update their account details.
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