IPA FE Subject A sample Question 39

Passing only the required data items as arguments — this is data coupling, the weakest kind of coupling between modules.

Coupling measures how much modules depend on each other. From weakest (best) to strongest:

• •Data coupling: only the needed data items are passed as arguments
• •Stamp coupling: a whole data structure is passed although only part of it is used
• •Control coupling: a flag is passed that decides the called module's logic
• •External coupling: modules share an externally defined data item or format
• •Common coupling: modules share data in a global area
• •Content coupling: one module refers directly to the inside of another

Answer (c)

Why not others:

• •(a) — cramming many functions into one module is not a kind of coupling at all; it lowers cohesion and makes the module hard to maintain and reuse
• •(b) — passing arguments that control the other module's logic is control coupling: the caller must know how the callee works inside
• •(d) — sharing data through a global area is common coupling: any module can change the data, so a change affects every module that uses it

Key rule: Aim for low coupling and high cohesion: pass modules only what they need, and keep each module to one well-defined function.

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