ITPEC FE Morning April 2021 Question 46

Topic: System Development Technology

The figure below shows an example of a DFD that uses one of the DFD notations and represents a flow of data in a system. Texts in the figure are not shown. Which of the following is represented by the circle “◯” in the DFD notation used in the example?

Explanation

Process — in this DFD notation the circle (bubble) is a process that transforms incoming data into outgoing data.

The DFD notation of structured analysis uses four symbols, and all of them appear in the figure:

SymbolMeaning
RectangleExternal entity: a source or destination of data outside the system
CircleProcess: turns input data flows into output data flows
Two parallel linesData store: data held for later use
ArrowData flow: data moving between the other elements

In the figure each circle receives at least one arrow and sends at least one, as a process must.

Answer (d)

Why not others:

  • •(a) Activity — not a DFD symbol; activities belong to UML activity diagrams, drawn as rounded rectangles
  • •(b) Data flow — drawn as the arrows between the symbols
  • •(c) Data store — drawn as the two parallel lines in the middle of the diagram

Key rule: Every DFD process has at least one input and one output flow, and data moves to or from a store or an external entity only through a process.

System Development Technology · AI-written, may contain errors

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