A-LevelComputer ScienceProgramming9618/22 · Oct/Nov 2021 · Q411 Marks

The following is a procedure design in pseudocode. Line numbers are given for reference only. 10 PROCEDURE Check(InString : STRING) 11 DECLARE Odds, Evens, Index : INTEGER 12 13 Odds ← 0 14 Evens ← 0 15 Index ← 1 16 17 WHILE Index <= LENGTH(InString) 18 IF STR_TO_NUM(MID(InString, Index, 1)) MOD 2 <> 0 THEN 19 Odds ← Odds + 1 20 ELSE 21 Evens ← Evens + 1 22 ENDIF 23 Index ← Index + 1 24 ENDWHILE 25 26 CALL Result(Odds, Evens) 27 ENDPROCEDURE

(a)Complete the following table by giving the answers, using the given pseudocode. A line number containing a variable being incremented The type of loop structure The number of functions used The number of parameters passed to STR_TO_NUM() The name of a procedure other than Check() Answer[5]
(b)The pseudocode includes several features that make it easier to read and understand. Identify three of these features. 1 2 3[3]
(c)(i)The loop structure used in the pseudocode is not the most appropriate. State a more appropriate loop structure and justify your choice. Loop structure Justification[2]
(c)(ii)The appropriate loop structure is now used. Two lines of pseudocode are changed and two lines are removed. Write the line numbers of the two lines that are removed.[1]

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2021). The mark or mark type is shown in brackets.

[1] A line number containing a variable being incremented: 19 / 21 / 23
[1] The type of loop structure: pre-condition
[1] The number of functions used: 3
[1] The number of parameters passed to STR_TO_NUM(): 1
[1] The name of a procedure other than Check(): Result
[1] Meaningful variable names
[1] Indentation / white space / blank lines
[1] Capitalisation of keywords
[1] Loop structure: A count-controlled loop
[1] Justification: The number of iterations is known // repeats for the length of InString
[1] 15, 23

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