ITPEC IP April 2019 Question 94

Processes joined by data flows, with a data file feeding one of them — the only figure drawn in DFD notation.

A DFD (data flow diagram) has four elements: external entities (rectangles), processes (circles), data flows (arrows labelled with the data they carry) and data stores (two parallel lines). Figure (b) has Data A flowing into Process 1, Data B from Process 1 to Process 2, Data C out of Process 2, and the store Data file 1 supplying Process 1: all DFD elements.

Answer (b)

Why not others:

• •(a) — circles for states and arrows labelled Event A to D form a state transition diagram
• •(c) — boxes for entities, a diamond for the relationship and the multiplicities 1 and N form an E-R diagram
• •(d) — a decision diamond branching to process boxes is a flowchart; it shows the order of control, not data

Key rule: A DFD shows what data moves, where it is transformed and where it is stored; it has no decisions, states or execution order.

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