ITPEC FE Subject B April 2026 Question 5

B, C, C, A — a procedure's own output runs only after the calls written above it have returned.

Expand proc1 step by step:

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

Note that proc3 runs twice: once from inside proc2 and once from proc1.

Answer (e)

Why not others:
- (a), (b) and (c) — place A first or second, but proc1 outputs last of all, after both of its calls have finished
- (f), (g) and (h) — start with C, which would require proc3 to run before proc2 printed; proc2 outputs B before calling proc3
- (d) — has B in third place, yet the second call made by proc1 is proc3, which prints C

Key rule: Read a call as "pause here, run the whole procedure, come back". Statements after the call wait; the deepest procedure prints first.

AI-generated — may contain errors