In systems analysis, which of the following is NOT a standard component of a Data Flow Diagram (DFD)?

Introduction / Context:
Data Flow Diagrams (DFDs) model how data moves through a system at a logical level. They purposely avoid implementation details (devices, programs) and instead emphasize processes, stores, flows, and external entities.

Given Data / Assumptions:

• DFDs show processes (circles/bubbles), data stores (parallel lines or open-ended rectangles), data flows (arrows), and external entities (terminators).
• DFDs are technology-agnostic; they do not depict physical hardware like disks/printers.
• We are selecting the item that does not belong to a DFD notation set.

Concept / Approach:
Differentiate logical modeling symbols (process, flow, store, external entity) from physical/hardware symbols (e.g., disk pack). A disk icon is common in flowcharting or physical system diagrams, not in logical DFDs.

Step-by-Step Solution:
1) List DFD primitives: process, data flow, data store, external entity.2) Compare each option against those primitives.3) Arrow, data store, and process bubble are core DFD symbols; external entity is also standard.4) A disk storage icon is a physical device representation, not part of logical DFD notation.

Verification / Alternative check:
DFD tutorials and textbooks consistently restrict symbols to the four logical primitives, reinforcing that device icons are excluded.

Why Other Options Are Wrong:
Arrow = data flow (correct DFD symbol). Data store = repository (correct). Process bubble = transformation (correct). External entity = source/sink (correct).

Common Pitfalls:
Mixing flowchart symbols (physical devices) with DFD symbols; attempting to show implementation specifics on a logical diagram.

Final Answer:
Disk storage symbol (physical device icon) is not a standard DFD component.