18.
Explanation
Data Flow Diagrams (DFDs) are graphical representations used in systems engineering and software engineering to depict the flow of data within a system.
Example: A simple example of a DFD might illustrate how a customer's order information flows through an online shopping system. It could show processes like "Add to Cart," "Checkout," and "Payment," as well as data stores like "Customer Database" and "Order History." Arrows between these elements would represent the flow of data from one process or data store to another.
