In structured design terminology, what is a “data couple,” and how does it relate to communication between modules?

Introduction / Context:
Structure charts and related design notations distinguish between control information and data being passed among modules. The term “data couple” identifies a specific kind of inter-module communication focused on the flow of data, not merely the existence of a call or control transfer. Understanding this helps designers minimize coupling and clarify module interfaces.

Given Data / Assumptions:

• Modules exchange information to perform a task.
• Some exchanges are control signals (e.g., flags), others are data (records, values).
• We want the definition that precisely captures data being passed between modules.

Concept / Approach:
A data couple represents a data item (or structured record) that flows from one module to another. It is usually annotated with the data name on the connector, making the contract explicit. In contrast, a simple line with no annotation conveys little; and the capability of a parent module to call a child module describes control hierarchy, not data coupling. Good design aims for low coupling: modules exchange only the data they need, in clear formats, to maintain cohesion and ease testing.

Step-by-Step Solution:
Identify which option mentions a data item moving between modules.Confirm that the definition distinguishes data flow from control flow.Select the option that states this explicitly.

Verification / Alternative check:
Structure-chart conventions label data couples with nouns (e.g., “customer_record”), while control couples carry verbs/flags (e.g., “error_flag”), reinforcing the distinction.

Why Other Options Are Wrong:
Unlabeled line: lacks semantics; not a definition.Parent calling child: control invocation, not data passing.None of the above: incorrect because a precise definition exists.

Common Pitfalls:
Passing overly broad records when only a few fields are needed; embedding control decisions inside data structures; or letting data couples proliferate to the point of tight coupling and fragile modules.

Final Answer:
A data item that moves from one module to another