ITPEC FE Subject B April 2026 Question 5

B, C, C, A — a call runs to completion before the statement after it starts, so proc1 prints its own A last.

• •proc1 first calls proc2
• •proc2 outputs B, then calls proc3, which outputs C
• •control returns to proc1, which calls proc3 directly: another C
• •only then does proc1 reach its own output statement: A

proc3 runs twice, once from inside proc2 and once from proc1.

Answer (e)

Why not others:

• •(a) and (b) — put A first, but proc1 outputs only after both of its calls have returned
• •(c) — puts A second, as if proc1 printed between its two calls
• •(d) — prints B again in third place, but the second call in proc1 is proc3, which prints C; nothing calls proc2 twice
• •(f), (g) and (h) — start with C, but proc2 outputs B before it calls proc3

Key rule: Read a call as "pause here, run the whole procedure, come back"; the order of statements inside each procedure decides whether its own output comes before or after the calls it makes.

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