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Questions and Answers
What is the primary purpose of a Level 0 Data Flow Diagram (DFD)?
What is the primary purpose of a Level 0 Data Flow Diagram (DFD)?
In a Level 1 DFD, which of the following rules must be followed?
In a Level 1 DFD, which of the following rules must be followed?
What is a characteristic of data flows in a Level 1 DFD?
What is a characteristic of data flows in a Level 1 DFD?
Which statement accurately describes the content of a Level 0 DFD?
Which statement accurately describes the content of a Level 0 DFD?
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What happens when data is transferred in a Level 1 DFD?
What happens when data is transferred in a Level 1 DFD?
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Study Notes
Data Flow Diagrams (DFDs)
- DFDs are diagrams used in planning and reporting for computer systems.
- They show how data flows through a system.
- Systems have data stored, and data moves around different components.
- Common symbols are used in diagrams.
Level 0 DFD
- Shows an overview of a system's operations.
- Example: a backup system overview.
- An IT technician uses File Manager to copy original files to another storage device.
Level 1 DFD
- Provides more detail than a Level 0 DFD.
- Example: a backup system with more components and actions.
- IT technician receives backup request, copies files, and sends to another location.
DFD Rules (Level 1)
- Each external entity (person/thing outside the system) has at least one input or output.
- Each process has at least one input or output.
Symbols
- Process: Actions or operations performed on data.
- External Entity: A person or thing outside the system that interacts with the system.
- Data Store: Where data is held (database, file).
- Data Flow: The transfer of data between components.
Data Flow Diagram Conventions
- Data flows in one direction.
- Data flows to and from processes.
- Data flows to and from data stores.
- All data flows are clearly labeled.
- Diagrams should avoid double-headed arrows.
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