A-LevelComputer ScienceProgramming9618/23 · May/June 2025 · Q69 Marks
Study the structure chart: [Figure showing a structure chart with Main, Sub_A, Sub_B modules, and parameters M, P, R, Q, V, X, W, T, U. Sub_A calls Sub_Part1A, Sub_Part2A, Sub_Part3A. Sub_B calls Sub_Part1B, Sub_Part2B. Diamond symbol under Main, curved line under Sub_A.] Some of the parameter data types are: • R and V are of type INTEGER • T is of type REAL • U is of type STRING • W is of type BOOLEAN. Some of the modules in the structure chart are functions, others are procedures.
- (a)Explain one difference between functions and procedures.[1]
- (b)Write the pseudocode to define the module headers: Sub_Part1A Sub_Part2A Sub_Part3A[5]
- (c)The structure chart uses the two symbols shown. Complete the table to explain what each symbol means and how the relevant modules in the structure chart are affected. Symbol Explanation [Diamond symbol] [Curved line under a box symbol][3]
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 (May/June 2025). The mark or mark type is shown in brackets.
- [1] MP1 A function returns a (single) value and a procedure does not
- MP2 A procedure can pass parameters by ByRef
- Max 1
- [5] Sub_Part1A: PROCEDURE Sub Part1A(R: INTEGER) 1 Mark
- Sub_Part2A: FUNCTION Sub Part2A(T : REAL) RETURNS BOOLEAN 2 Marks
- Sub_Part3A: PROCEDURE Sub Part3A(V: INTEGER, W: BOOLEAN, BYREF U : STRING) 2 Marks
- [3] Symbol: [Diamond] Explanation: The module Main calls either Sub_A or Sub_B (which one is called is determined at run time)
- Symbol: [Curved line under a box] Explanation: The module Sub_A will repeatedly call Sub_Part1A followed by Sub_Part2A then by Sub_Part3A
- MP1 Shape1: reference to selection
- MP2 Shape2: reference to repetition // iteration
- MP3 Descption (x2) including correct use of all module names in both parts
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