Final answer:
A data flow diagram (DFD) is a graphical representation of the flow of data within a system. It includes symbols such as Process, Data Store, Data Flow, and Decision. The symbol not included in a DFD is Decision.
Step-by-step explanation:
A data flow diagram (DFD) is a graphical representation of the flow of data within a system. It is used to show how data is input, processed, stored, and output. The symbols used in a DFD include:
- Process: represents a specific function or task that takes in data and produces an output. It is represented by a rectangle with rounded corners.
- Data Store: represents a place where data is stored or retrieved. It is represented by a rectangle with perpendicular lines.
- Data Flow: represents the movement of data between processes, data stores, and external entities. It is represented by an arrow.
- Decision: represents a point in the system where a decision is made based on certain conditions. It is represented by a diamond shape.
Therefore, the correct answer is option 4) Decision.
In a Data Flow Diagram (DFD), the 'Decision' symbol is not used. DFDs use 'Process', 'Data Store', and 'Data Flow' symbols to represent the flow and transformation of information within a system, not the decision-making process.
In the context of a Data Flow Diagram (DFD), the symbol that is not used is Decision. A DFD is primarily concerned with the flow of information within a system, and it typically contains three types of symbols:
Process - Represents a part of the system that processes the data, typically a function or a task.
Data Store - Depicts where data is stored within the system.
Data Flow - Illustrates the movement of data between processes, data stores, and external entities.
DFDs do not typically include a Decision symbol because they are not concerned with decision-making processes or control flow like flowcharts do. Instead, DFDs show how data moves and is transformed within the system.