A-LevelComputer ScienceAlgorithm design and problem-solving9618/22 · Oct/Nov 2023 · Q27 Marks

An algorithm will: 1. input a sequence of integer values, one at a time 2. ignore all values until the value 27 is input, then sum the remaining values in the sequence 3. stop summing values when the value 0 is input and then output the sum of the values.

(a)Draw a program flowchart to represent the algorithm.[5]
(b)The solution to the algorithm includes iteration. Give the name of a suitable loop structure that could be used. Justify your answer. Name Justification[2]

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Mark scheme

Marking points from the official mark scheme (Oct/Nov 2023). The mark or mark type is shown in brackets.

[5] One mark per point:
1 Initialise Total to zero
2 Check for only first input of 27 in a loop then attempt to sum values
3 Loop until 0 input
4 Sum values input (after input of first 27) in a loop
5 Output Total after a reasonable attempt
[2] One mark per point:
1 Name: (pre / post) conditional loop
2 Justification: the number of iterations is not known // loop ends following a specific input (in the loop)

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Topic: Algorithm design and problem-solving, A-Level Computer Science (syllabus 9618). Structured question, 7 marks.
Source: A-Level Computer Science, Oct/Nov 2023 Paper 2 Variant 2, question 2.

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