ITPEC FE Subject B April 2024 Question 5

Converting total seconds into hours, minutes, and seconds using integer division and modulus.

The program converts a value in seconds (e.g., 5450) into hour, minute, second format (e.g., 1, 30, 50).

Step-by-step with `convert(5450)`:

1. second ← modulus(input, 60) → 5450 mod 60 = 50 — extracts the remaining seconds.
2. A (minute): First, division(input, 60) = integer part of (5450 ÷ 60) = 90 — total minutes. Then modulus(90, 60) = 30 — minutes without full hours. So A = modulus(division(input, 60), 60).
3. B (hour): division(input, 3600) = integer part of (5450 ÷ 3600) = 1 — full hours. So B = division(input, 3600).

Why not others:
- (a) A = division(modulus(input, 60), 60) → division(50, 60) = 0, not 30
- (b) Same A as (a), fails for the same reason
- (c) Same A as (a); B = modulus(division(input, 60), 60) gives minutes (30), not hours
- (e) A is correct, but B = division(modulus(input, 60), 60) → division(50, 60) = 0, not 1
- (f) A is correct, but B = modulus(division(input, 60), 60) → 30 (minutes, not hours)

Key rule: To extract a middle unit (minutes from seconds), divide first to remove the smaller unit, then use modulus to remove the larger unit. For the largest unit (hours), divide by the full conversion factor (3600).

AI-generated — may contain errors