A-LevelComputer ScienceAlgorithm design and problem-solving9618/21 · May/June 2024 · Q27 Marks

An algorithm has three steps. It will: 1. repeatedly input a pair of numeric values A and B 2. count the number of pairs that are input until A has been greater than B 10 times 3. output the number of pairs that were input.

(a)Complete the program flowchart.[5]
(b)Step 1 of the algorithm is changed. A variable ThisSequence is used to enter a sequence of 10 pairs of numeric values, using a single input statement. Following the input of ThisSequence the revised algorithm will extract the pairs of numbers. Describe the variable ThisSequence and how the numbers are extracted.[2]

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Mark scheme

Marking points from the official mark scheme (May/June 2024). The mark or mark type is shown in brackets.

[5] One mark per outlined region:
1 Initialise both counts
2 Increment Tries every time a pair is input
3 Compare A > B and increment Count if TRUE
4 Test for Count = 10 (10th time A > B) – MUST include Yes / No labels
5 If so output Tries, otherwise loop
[2] One mark per point:
1 A (variable of type) string will be input // by example e.g. “67,72”
2 A special / identified character would need to be used to separate each numeric value // all numbers are fixed length

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