O-LevelComputer ScienceAlgorithm design and problem-solving2210/22 · Oct/Nov 2018 · Q57 Marks

The flowchart checks the level of chlorine and the depth of water compared to the height of the swimming pool. Error messages are output if a problem is found.

(a)Complete the trace tables for each set of input data. Input data: 6, 2.5, 2 Height Depth Chlorine OK OUTPUT Input data: 4, 3, 1.5 Height Depth Chlorine OK OUTPUT Input data: 6, 3.5, 4 Height Depth Chlorine OK OUTPUT[6]
(b)Identify a problem with the algorithm that the flowchart represents.[1]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2018). The mark or mark type is shown in brackets.

[1] 1 mark for first 4 columns in each trace table (max 3)
[1] 1 mark for the output in each trace table (max 3)
Input 6, 2.5, 2: Height: 6, Depth: 2.5, Chlorine: 2, OK: True, OUTPUT: Pool OK to use
Input 4, 3, 1.5: Height: 4, Depth: 3, Chlorine: 1.5, OK: False, OUTPUT: Water too deep
Input 6, 3.5, 4: Height: 6, Depth: 3.5, Chlorine: 4, OK: False, OUTPUT: Water too deep
[1] Any one from:
[1] Cannot add more water if the water is too deep
[1] No validation e.g. allows a negative height/depth/amount of chlorine
[1] Tells you to add chlorine when there is no water
[1] Runs only once

On Oracle Prep you can write or photograph your own answer and have it marked by AI against this mark scheme, with feedback on what you missed.