Which diagram type visualizes data flow and communication between various software modules?

A data flow diagram is designed specifically to represent the flow of data between processes, data stores, and external entities within a system. It effectively showcases how information moves through different software modules, making it easier to understand the interactions and communication channels in a system. This type of diagram illustrates which processes receive data, where it is stored, and how it's transformed, providing clarity on the relationships between various components of the software architecture.

In contrast, class diagrams focus on the structure of a system by describing the classes, their attributes, methods, and the relationships between them. UML diagrams can include various types of diagrams, such as class diagrams and state diagrams, but they don’t specifically emphasize data flow. Deployment diagrams, on the other hand, emphasize the physical deployment of artifacts on nodes instead of the data or communication between components. Each of these other diagram types serves a distinct purpose that does not directly visualize data flow and communications like the data flow diagram does.