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Cambridge International AS & A Level

COMPUTER SCIENCE 9618/23

Paper 2 Fundamental Problem-solving and Programming Skills October/November 2024
MARK SCHEME
Maximum Mark: 75

Published

This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the
examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the
details of the discussions that took place at an Examiners’ meeting before marking began, which would have
considered the acceptability of alternative answers.

Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for
Teachers.

Cambridge International will not enter into discussions about these mark schemes.

Cambridge International is publishing the mark schemes for the October/November 2024 series for most
Cambridge IGCSE, Cambridge International A and AS Level components, and some Cambridge O Level
components.

This document consists of 14 printed pages.

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Cambridge International AS & A Level – Mark Scheme
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Generic Marking Principles

These general marking principles must be applied by all examiners when marking candidate answers.
They should be applied alongside the specific content of the mark scheme or generic level
descriptions for a question. Each question paper and mark scheme will also comply with these
marking principles.

GENERIC MARKING PRINCIPLE 1:

Marks must be awarded in line with:

• the specific content of the mark scheme or the generic level descriptors for the question
• the specific skills defined in the mark scheme or in the generic level descriptors for the question
• the standard of response required by a candidate as exemplified by the standardisation scripts.

GENERIC MARKING PRINCIPLE 2:

Marks awarded are always whole marks (not half marks, or other fractions).

GENERIC MARKING PRINCIPLE 3:

Marks must be awarded positively:

• marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit
is given for valid answers which go beyond the scope of the syllabus and mark scheme,
referring to your Team Leader as appropriate
• marks are awarded when candidates clearly demonstrate what they know and can do
• marks are not deducted for errors
• marks are not deducted for omissions
• answers should only be judged on the quality of spelling, punctuation and grammar when these
features are specifically assessed by the question as indicated by the mark scheme. The
meaning, however, should be unambiguous.

GENERIC MARKING PRINCIPLE 4:

Rules must be applied consistently, e.g. in situations where candidates have not followed
instructions or in the application of generic level descriptors.

GENERIC MARKING PRINCIPLE 5:

Marks should be awarded using the full range of marks defined in the mark scheme for the question
(however; the use of the full mark range may be limited according to the quality of the candidate
responses seen).

GENERIC MARKING PRINCIPLE 6:

Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should
not be awarded with grade thresholds or grade descriptors in mind.

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Mark scheme abbreviations

/ separates alternative words / phrases within a marking point

// separates alternative answers within a marking point
underline actual word given must be used by candidate (grammatical variants accepted)
max indicates the maximum number of marks that can be awarded
() the word / phrase in brackets is not required, but sets the context

Note: No marks are awarded for using brand names of software packages or hardware.

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Question Answer Marks

1(a) 4
Pseudocode example Selection Iteration Subroutine

FOR Index  1 TO 3
IF Safe[Index] = TRUE THEN
Flap[Index]  0  
ENDIF
NEXT Index

CASE OF Compound(3)  

REPEAT UNTIL AllDone() = TRUE  

WHILE Result[3] <> FALSE 

One mark per row

1(b) 3
Variable Example data value Data type

Available TRUE BOOLEAN

Received "18/04/2021" STRING

Index 100 INTEGER

One mark per row

1(c) 3
Expression Evaluates to

Available AND NOT(Index > 100) TRUE

Index MOD 30 10

NUM_TO_STR(Index + "33") ERROR

One mark per row

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Question Answer Marks

2(a) DECLARE Count, Total, NextNumber : INTEGER 5

Total  0
FOR Count  1 TO 100
OUTPUT "Input an integer value"
INPUT NextNumber
IF NextNumber > 0 THEN
Total  Total + NextNumber
ENDIF
NEXT Count

OUTPUT Total

Mark as follows:
MP1 Declarations of all variables used
MP2 Loop for 100 iterations
MP3 Prompt and input a value in a loop and
MP4 Test for value > 0 // >=1 in a loop
MP5 Sum the Total in a loop
MP6 Output of Total after the loop

Max 5 marks

2(b) MP1 Construct: Iteration / Repetition 2

MP2 Use: To loop through all 100 inputs // To loop 100 times

ALTERNATIVE:

MP1 Construct: Selection

MP2 Use: To test whether the value input is positive

Question Answer Marks

3(a)(i) 0 is not a valid array / List index value // No 0th element in the array 1

3(a)(ii) 0 to 200 1

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Question Answer Marks

3(b) 4

Mark as follows:
MP1 Use of variable as array index and initialisation to 1 / to first element of
array
MP2 Loop for 199 / 200 iterations
MP3 Assign Index+1 to each pointer field in a loop
MP4 Assign 0 to 200th pointer field

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Question Answer Marks

3(c) One mark per step: 4

MP1 Assign HeadPointer to ThisPointer / Current Pointer // Identify

first node using headpointer

MP2 Loop the following until ThisPointer value is 0 (zero) / null pointer
reached

MP3 … Output data (field) from array element at index ThisPointer //

Output data (field) of the current node / array element

MP4 … Assign pointer field from current array element / index / to

ThisPointer / Current Pointer // Assign pointer field from current
node to ThisPointer / Current Pointer

4(a) One mark per highlighted part: 4

FOR Index  1 TO 5
Lower  GB[Index] - 2
Upper  GB[Index] + 2 // Lower + 4
IF Mark >= Lower AND Mark <= Upper THEN
//IF Mark <= Upper AND Mark >= Lower THEN
OUTPUT "Check this paper"
ENDIF
NEXT Index

4(b)(i) MP1 Use Mark as the index to the Check array // to specify an array 2
element

MP2 If value of indexed element is TRUE, then the paper will need to be
checked

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Question Answer Marks

4(b)(ii) Example:solution 6

PROCEDURE GBInitialise()
DECLARE GBIndex, GBMark, ThisIndex : INTEGER

FOR ThisIndex  0 TO 75
Check[ThisIndex]  FALSE // initialise all values
NEXT ThisIndex

FOR GBIndex  1 TO 5
GBMark  GB[GBIndex]
FOR ThisIndex  GBMark - 2 TO GBMark + 2
Check[ThisIndex]  TRUE //Set GBMark  2 to
TRUE
NEXT ThisIndex
NEXT GBIndex
ENDPROCEDURE

Mark as follows:
MP1 Procedure heading and ending
MP2 Initialise Check array to FALSE
MP3 Loop through GB array
MP4 Extract the GB mark
MP5 Loop for 5 elements across GBMark  2 // Check if within GBMark
2
MP6 Assign each element of Check array to TRUE

ALTERNATIVE – Example using selection Version 1

FOR ThisIndex  0 TO 75
CASE ThisIndex
GB[1] – 2 TO GB[1] + 2 : Check[ThisIndex]  TRUE
GB[2] – 2 TO GB[2] + 2 : Check[ThisIndex]  TRUE
GB[3] – 2 TO GB[3] + 2 : Check[ThisIndex]  TRUE
GB[4] – 2 TO GB[4] + 2 : Check[ThisIndex]  TRUE
GB[5] – 2 TO GB[5] + 2 : Check[ThisIndex]  TRUE
OTHERWISE: Check[ThisIndex]  FALSE
ENDCASE
NEXT ThisIndex

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Question Answer Marks

4(b)(ii) ALTERNATIVE – Example using selection Version 2

DECLARE ThisIndex, GBIndex : INTEGER

DECLARE Lower, Higher : INTEGER

FOR ThisIndex  0 TO 75
For GBIndex  1 T0 5
Lower  GB[GBIndex] - 2
Higher  GB[GBIndex] + 2
IF ThisIndex >= Lower AND ThisIndex <= Higher
THEN
Check[ThisIndex]  TRUE
ELSE
Check[ThisIndex]  FALSE
ENDIF
NEXT Index
NEXT ThisIndex

Mark as follows:
MP1 Procedure heading and ending
MP2 Loop through Check array// loop from 0 to 75
MP3 Attempt at using CASE / Selection structure with five clauses/ five
checks for range
MP4 Extract GB grade
MP5 Compare ThisIndex with each element in GB array 2
MP6 Assign each element of Check array to TRUE if in range or FALSE if
not in range

Question Answer Marks

5(a) 4
Name of life
Activity
cycle stage

A compiler is be used. Coding

A program that has been released for general use

Maintenance
is modified

The dry run method is used. Testing

The program structure is specified. Design

One mark per row

5(b) One mark for method – two marks for the description 3

MP1 Stub testing

MP2 The modules Test_A() and Test_B()are replaced by dummy
modules
MP3 ... which return a known result // An output statement is displayed
when called (to check it works) // gives expected output

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Question Answer Marks

6 Loop Solution 7
Example solution:

FUNCTION AdjustClock(ThisYear : INTEGER) RETURNS INTEGER

DECLARE ThisDayNumber, SundayCount : INTEGER
DECLARE ThisDate : DATE

ThisDayNumber  0
SundayCount  0
REPEAT
ThisDayNumber  ThisDayNumber + 1
ThisDate  SETDATE(ThisDayNumber, 3, ThisYear)
IF DAYINDEX(ThisDate) = 1 THEN
SundayCount  SundayCount + 1
ENDIF
UNTIL SundayCount = 3
RETURN ThisDayNumber
ENDFUNCTION

Mark as follows:
MP1 Function heading, parameter, ending and return type
MP2 Declare local integer variable that is used to create a date
MP3 Loop until 3rd Sunday found
MP4 Attempt to use both SETDATE() and DAYINDEX() in a loop
MP5 Correctly generate value of type DATE using SETDATE() in a loop
MP6 Test if value represents a Sunday using DAYINDEX() in a loop
MP7 Increment Sunday count in a loop and initialised correctly before loop
MP8 Return day number of third Sunday

Max 7 marks

Non-loop solution
Example solution:

FUNCTION AdjustClock(ThisYear : INTEGER) RETURNS INTEGER

DECLARE FirstDayIndex: INTEGER
DECLARE ThisDate : DATE

ThisDate  SETDATE(1, 3, ThisYear)

FirstDayIndex  DAYINDEX(ThisDate)
IF FirstDayIndex = 1 THEN
ThirdSunday  FirstDayIndex + 14 //First day is
Sunday
ELSE
ThirdSunday  23 – FirstDayIndex // Other days
ENDIF
RETURN ThirdSunday
ENDFUNCTION

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Question Answer Marks

6 Mark as follows:
MP1 Function heading, parameter, ending and return type
MP2 Declare local integer variable that is used to hold a day number
MP4 Attempt to use both SETDATE() and DAYINDEX()
MP5 Correctly generate value of type DATE using SETDATE() for first of
March / specific day in March
MP6 Test if date represents a Sunday / specific day using DAYINDEX()
and calculate third Sunday // Correctly calculate third Sunday for a
value returned by DAYINDEX()for one day
MP7 Calculate third Sunday for other six days
MP8 Return day number of third Sunday

Max 7 marks

Question Answer Marks

7(a) One mark per answer: 2

MP1 Analysis

MP2 Named document, examples include:

• A requirement specification
• Definition of System Objectives
• List of problems with existing system
• Survey results
• Feasibility study
• Interview notes

Max 2 marks

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Question Answer Marks

7(b) One mark for name and use 4

Mark as follows:
Examples include:

Sub-module: ScanCard()/ GetID()

Use: Read the barcode from the loyalty card / Get the customer ID from the
barcode

Sub-module: GetPoints()
Use: Get the number of points the customer has

Sub-module: ExchangePoints() / UpdateCard()

Use: Reduce the number of loyalty points

Sub-module: GetDiscount() / CalculateDiscount()

Use: Calculate the discount

Sub-module: CalculatePoints()
Use: Calculate points (following a purchase)

Sub-module: UpdatePoints()
Use: Update total points a customer has (following a purchase)

Sub-module: ShowDiscount()
Use: Display the discount

Max 4 marks

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Question Answer Marks

8(a) Example solution 7

PROCEDURE Count(ThisPlayer : INTEGER, ThisRole : STRING)

DECLARE Index, Num, Total : INTEGER

Num  0
Total  0

FOR Index  1 TO 45
IF Character[Index].Player = ThisPlayer AND __
Character[Index].Role = ThisRole THEN
Num  Num + 1
Total  Total + Character[Index].SkillLevel
NEXT Index

IF Num > 0 THEN

OUTPUT "Player ", ThisPlayer, __
" has ", Num, " characters with the role of
", ThisRole, " and the total skill level is
", Total
ELSE
OUTPUT "No characters with that role are
assigned to this player"
ENDIF

ENDPROCEDURE

MP1 Initialisation of local integers for Num and Total

MP2 Loop through 45 elements

MP3 Attempt to check Player and Role fields in a loop

MP4 Correctly compare Player field with parameter in a loop
MP5 Correctly compare Role field with parameter in a loop

MP6 ... if player and role found, increment Num and sum Skill Total in a
loop
MP7 Test for any matches after the loop
MP8 Both possible OUTPUT statements correctly formed following an
attempt at MP6 but outputting one only

Max 7 marks

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Question Answer Marks

8(b) Example solution: 7

PROCEDURE Restore()
DECLARE Index : INTEGER
DECLARE Line : STRING

OPENFILE "SaveFile.txt" FOR READ

FOR Index  1 TO 45
READFILE "SaveFile.txt", Line
Character[Index].Player  STR_TO_NUM(Extract(Line,
1))
Character[Index].Role  Extract(Line, 2)
Character[Index].Name  Extract(Line, 3)
Character[Index].Skill  STR_TO_NUM(Extract(Line,
4))
NEXT Index

CLOSEFILE "SaveFile.txt"

ENDPROCEDURE

Mark as follows:
MP1 Open the file in read mode and subsequently close
MP2 Loop through 45 elements
MP3 Read a line from the file in a loop
MP4 Attempt to use Extract() in a loop
MP5 Correct use of Extract() for all fields in a loop
MP6 Use of STR_TO_NUM() on Player and Skill in a loop
MP7 Completely correct extraction and assignment of all fields in a loop

8(c) MP1 The Character array / character data can be saved before the 2
program is closed
MP2 Allowing the game to continue using the same data / from the point it
was saved

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