Exam questions: Thinking logically

Question 1

4 marks

1 4 marks

Eve enjoys playing board games. Her favourite board game is called “Pot Luck”. This has a numbered grid of 10 squares by 10 squares. Each square has a number between 1 and 100.

Players place their game counters on square 1. A 30-minute timer is set which counts downwards. Each player rolls two 6-sided dice and then moves their game counter that number of squares. Some squares tell the player to pick up a card. These have instructions on, such as 'Move forward 10 spaces'. If the player lands on one of these squares they move according to the instruction on the card. The first player to land on square 100, is announced as the winner. If no winner is announced before the timer runs out, then it is a draw.

Logical conditions are checked once a player has rolled the dice.

Describe two different logical conditions and how the result will affect the outcome of the game.

Logical Condition 1

Condition:

Outcome:

Logical Condition 2

Condition:

Outcome:

Your answer

Mark scheme 1

Tick each point your answer makes. Your mark is worked out from your ticks, and you can change it.

1 mark for condition and 1 mark for outcome to max 4
e.g.

Condition: Check if the square has an instruction ...
Outcome: ... move the player the number of places specified
Condition: Check if they have landed on square 100 ...
Outcome: ... Announce the player as the winner
Condition: Check if the timer is 0 ...
Outcome: ... Announce the game as a draw

Guidance

Allow other suitable examples that are relevant to the scenario.

The outcome must be related to the condition for a mark to be awarded.

Examiner’s Comments

Some candidates did not present clear conditions but gave
descriptions of actions to perform within the game such as ‘roll dice’. The condition required an identification within the context of something that would lead to a Boolean result with consequent outcome. For example, if the timer runs out then the game will end in a draw.

Your mark for 1

out of 4

Question 2

40 marks

2(b)

The characters and prizes are designed as separate classes. 10 of the spaces on the road will contain an instance of the class Prize. The other spaces will be empty.

The class design for Prize is here.

class: Prize

attributes:
private name : string
private type : string
private value : integer

methods:
new()
getName()
getType()
getValue()

new() is the constructor method. The name, type and value are passed to the constructor as parameters which then assigns these to the attributes.

2(b)(i) 2 marks

The method getName() returns the data in the attribute name.
Write the method getName() using pseudocode or program code.

Your answer

Mark scheme 2(b)(i)

Tick each point your answer makes. Your mark is worked out from your ticks, and you can change it.

1 mark each

Function/subroutine with identifier getName taking no parameters
Returning name

e.g.

public function def
getName()         getName(self):
return
return name
self.__name
endfunction
public           function
getName(){        getName() {
return name       return this.name

} }

Guidance

BP1 Do not award procedure or method

BP1 Allow self as an additional parameter if Python is used.

BP1 If an access modifier is given for the method, it must be public and not private.

BP2 Do not allow any modified name attribute to be returned.

Examiner’s Comments

While many candidates had little difficulty giving code for a getter() there were a number of common errors. Some candidates used a private access modifier when a getter() needs to be public. There was often erroneous use of ‘procedure’ whereas a getter() is a function that must return a value.
Some candidates tried to set values within the getter() function when it should only have returned the class attribute value.

Your mark for 2(b)(i)

out of 2

2(b)(ii) 3 marks

A global 1-dimensional array, allPrizes, stores 10 objects of type Prize.

The prize in index 3 has the name “Box”, the type is “money” and the value is 25.

Write pseudocode or program code to create a new object for this prize and store it in index 3 of

allPrizes.

Your answer

Mark scheme 2(b)(ii)

Tick each point your answer makes. Your mark is worked out from your ticks, and you can change it.

1 mark each

New instance of prize …
… with “Box”, “money” and 25 as parameters
Assigned to allPrizes index 3

e.g.

allPrizes[3] = new prize("Box",
"money", 25)
allPrizes[3] = prize.new("Box",
"money", 25)
allPrizes[3] = prize("Box",
"money", 25)

Guidance

MP2 allow any order of parameters

"Box" and "Money" must be strings and 25 must be an integer

Allow prize.new() as new is given as the constructor method in the class diagram

Examiner’s Comments

Many candidates struggled with the instantiation of an object. Where candidates made an attempt to instantiate some did not use a string for “box” and “money” or did not give 25 as an integer but instead gave the string “25”.

Your mark for 2(b)(ii)

out of 3

2(b)(iii) 3 marks

The game starts with 10 prizes. Each prize is allocated to one space on the road.

An algorithm needs designing that will generate a random space on the road for each prize. Each road space can only store one prize.

Describe the decisions that will need to be made in this algorithm and how these will affect the program flow.

Your answer

Mark scheme 2(b)(iii)

Tick each point your answer makes. Your mark is worked out from your ticks, and you can change it.

1 mark for each bullet to maximum 3 e.g.

Decision - check whether the space already has a prize allocated …
Action if true - another space/number will need to be generated
Action if false - the prize will be stored here
Decision - check if all 10 prizes have been allocated …
Action if true - the algorithm needs to stop generating numbers
Action if false - a new number/space needs to be generated and checked

Guidance

Give:

1 mark for stating a decision
1 mark for the action required if true
1 mark for the action required if false

Examiner’s Comments

There were only two reasonable decisions that could be given from the scenario details. Candidates needed to make it clear that a decision with a Boolean output was present that would dictate two potential outcomes. Some candidates quoted actions such as ‘randomly assign space for prize’ which did not represent a decision. Many responses described the mechanics of setting up the game and the random spaces but did not highlight the program
conditions/decisions as required.

Your mark for 2(b)(iii)

out of 3

2(c)

The class design for Character is here.

class: Character

attributes:
private name : string
private money : integer
private experience : integer
private roadPosition : integer

methods:
new()
getName()
getMoney()
getExperience()
getRoadPosition()
changePosition()
updateValues()

The four get methods return the associated attribute.

The number of moves is passed to changePosition() as a parameter. The method adds this value to the character’s position on the road.

The type and value of an object are passed to updateValues() as parameters. If the object is money the value is added to the character’s money. If the type is experience the value is added to experience. If the type is neither money or experience no changes are made.

2(c)(i) 5 marks

new() is the constructor method. The name of the character is passed into the constructor as a parameter. The constructor then initialises both the experience and road position of the character to 0 and initialises the amount of money to 5.

Write the constructor method for Character using either pseudocode or program code.

You do not need to declare the class, the attributes or any other methods.

Your answer

Mark scheme 2(c)(i)

Tick each point your answer makes. Your mark is worked out from your ticks, and you can change it.

1 mark each

Constructor header (any suitable name e.g. new, constructor, create, init)
…taking one parameter only
Initialising name to the parameter
Initialising money to 5
Initialising experience to 0 and roadPosition to 0

e.g.

public procedure
new(pName)
name = pName

Pseudocode

experience = 0

example:

roadPosition = 0
money = 5
endprocedure
def __init__(self,
pName):

Python self.__name = pName Example: self.__experience = 0

self.__roadPosition = 0
self.__money = 5
public Character(string

C# pName) {
Example: string name = pName;

int experience = 0;

int roadPosition = 0;
int money = 5;
 }

Guidance

Allow minor changes to identifiers as long as purpose is clear.

Allow

procedure new(pName)
this.name = pName

…
(or similar e.g. self.name)

Allow two parameters if one is self and the response is clearly in Python.

The parameter name should be different to the attribute name.

Examiner’s Comments

It was clear that those candidates with limited OOP programming knowledge found the writing of a relatively simple constructor method difficult. Those with relevant programming experience often found this to be a very
straightforward question. Common errors included passing additional values to set the experience,

roadPosition and money

attributes rather than setting them to

the constant values indicated in the question.

Your mark for 2(c)(i)

out of 5

2(c)(ii) 5 marks

The type and value of a prize are passed as parameters to the method updateValues. If the type is money the value is added to the character’s money. If the type is experience then the value is added to the experience. If the type is neither money or experience no changes are made.

For example, for the Character player1:

player1.updateValues("money",10) updates player1’s money by 10

player1.updateValues("experience",5) updates player1’s experience by 5

player1.updateValues("foo",9) has no effect on player1.

Write pseudocode or program code for the method updateValues().

Your answer

Mark scheme 2(c)(ii)

Tick each point your answer makes. Your mark is worked out from your ticks, and you can change it.

1 mark each

Procedure/method header …
… taking two parameters, type (or similar) followed by value (or similar) …
… compare type parameter with "money"
… compare type parameter with

"experience"

… both attributes updated correctly and nothing else modified

e.g.

public procedure
updateValues(pType, pValue)
if pType == "money" then
money = money + pValue
elseif pType == "experience"
experience = experience + pValue
endif
endprocedure

def updateValues(self, pType,
pValue):
if pType == "money":
money += pValue
elif pType == "experience":
experience += pValue

Guidance

Do not allow Function for BP1

BP2 parameters must be given in the correct order to match the calls to updateValues() in the question.

“money” and “experience” must be string values

Examiner’s Comments

The updateValues procedure again proved problematic for candidates with limited OOP experience. No marks were given for the first mark point if a function was declared as there was no return value. Parameter names needed to be fit for purpose, understandable, and had to match the order given in the question scenario to work for the given example calls.

Your mark for 2(c)(ii)

out of 5

2(d) 6 marks

This incomplete pseudocode algorithm:

creates a new character with the name Jamal
loops until the character reaches the end of the road
generates a random number of spaces to move between 1 and 4 (including 1 and 4)
moves the character and checks if the new space has a prize
updates the character attributes if there is a prize
outputs the character’s new attribute values.

Complete the pseudocode algorithm.

character1 = new …… ("Jamal")
newPosition = 0
while newPosition < ……
  move = random(1, 4) /this will generate a random number between 1 and 4
  character1.changePosition(move)
  newPosition = character1.getRoadPosition()
  if newPosition < 50 and road[……] != null then
    prizeType = road[newPosition].getType()
    valueAmount = road[newPosition].getValue()
    character1.updateValues(……, valueAmount)
    print("Congratulations you are in position", newPosition, "and found",
      road[newPosition].getName())
    print("Money =", character1.getMoney(), "and experience =",
      character1. …… ())
  endif
……
print("You reached the end of the road")

Your answer

Mark scheme 2(d)

Tick each point your answer makes. Your mark is worked out from your ticks, and you can change it.

1 mark for each completed space

character1 = new
Character("Jamal")
newPosition = 0
while newPosition < 50
move = random(1, 4)
character1.changePosition(move)
newPosition =
character1.getRoadPosition()
if newPosition < 50 and
road[newPosition] != null
then
prizeType =
road[newPosition].getType()
valueAmount =
road[newPosition].getValue()
character1.updateValues(prizeType,
valueAmount)

print("Congratulations you are in
position",
newPosition, "and found",
road[newPosition].getName())
print("Money",
character1.getMoney(), "and
experience",
character1.getExperience())
endif
endwhile
print("You reached the end of the
road")

Guidance

Allow road.length /
len(road) instead of 50

Allow <=49 instead of < 50

Examiner’s Comments

Nearly all candidates achieved some marks, and a majority scored five or six marks.

Your mark for 2(d)

out of 6

2(e) 4 marks

The procedure displayRoad() outputs the contents of each space in the road. The number of each space is output with either:

the word “empty” if there is no prize
the name of the prize if there is a prize.

01  procedure displayRoad()
02     for x = 0 to 60
03        print("Space", y)
04        if road[x] == null then
05         print("empty")
06        elseif
07         print(road[x].getValue())
08        endif
09     next x
10  endprocedure

The algorithm contains errors.

Give the line number of four different errors and write the corrected line for each error.

Error 1

Error line 1

Correction

Error 2

Error line 2

Correction

Error 3

Error line 3

Correction

Error 4

Error line 4

Correction

Your answer

Mark scheme 2(e)

Tick each point your answer makes. Your mark is worked out from your ticks, and you can change it.

1 mark each

(Line 02) for x = 0 to 49
(Line 03) print("Space", x)
(Line 06) else / elseif road[x]

<> null

(Line 07)

print(road[x].getName())

Guidance

Line 07 allow

print(road[x].name)

Examiner’s Comments

Many candidates scored three or four marks but in general candidates found it harder to identify errors in the code than to complete code in the previous question. Some candidates didn’t give the line number but rewrote the incorrect line before giving the corrected line, which was acceptable, although not ideal given the scaffolding.

Your mark for 2(e)

out of 4

2(f) 9 marks

A programmer is going to create a prototype for one small part of the game. Both road and allPrizes will be needed throughout the whole prototype. The programmer is considering making these global arrays as she thinks it will reduce the development time. Another programmer has suggested that doing this may create some problems when the rest of the game is created at a later stage.

Compare the use of global and local variables in this program.

You should include the following in your answer:

the use of local and global variables
alternative methods to using global variables
the appropriateness of each to this program design.

Your answer

Mark scheme 2(f)

Tick each point your answer makes. Your mark is worked out from your ticks, and you can change it.

Mark Band 3 – High level (7-9 marks) The candidate demonstrates a thorough knowledge and understanding of global variables and the alternatives; the material is generally accurate and detailed.
The candidate is able to apply their knowledge and understanding directly and consistently to the context provided. Evidence/examples will be explicitly relevant to the explanation. There is a well-developed line of reasoning which is clear and logically structured. The information presented is relevant and substantiated.

Mark Band 2 – Mid level (4-6 marks) The candidate demonstrates reasonable knowledge and understanding of global variables and the alternatives; the material is generally accurate but at times
underdeveloped.
The candidate is able to apply their knowledge and understanding directly to the context provided although one or two opportunities are missed. Evidence/examples are for the most part implicitly relevant to the

explanation.
The candidate provides a reasonable discussion, the majority of which is focused. Evaluative comments are, for the most part appropriate, although one or two opportunities for development are missed.

There is a line of reasoning presented with some structure. The information presented is in the most part relevant and supported by some evidence.

Mark Band 1 – Low Level (1-3 marks) The candidate demonstrates a basic knowledge of global variables and the alternatives with limited understanding shown; the material is basic and contains some inaccuracies. The candidates makes a limited attempt to apply acquired knowledge and understanding to the context provided. The candidate provides a limited discussion which is narrow in focus.
Judgements if made are weak and
unsubstantiated.

The information is basic and comunicated in an unstructured way. The information is supported by limited evidence and the relationship to the evidence may not be clear.

0 mark
No attempt to answer the question or response is not worthy of credit.

Guidance

AO1: Knowledge and
Understanding
Indicative content

Global variables are created when the program starts, all subroutines can access/update the contents
Local variables are created in the subroutine they are created in, they are not accessible directly from any other subroutine
Local variables are removed from memory when the subroutine ends.
Local variables can be passed as parameters to a function to be updated, and then returned to override the original local variable
Local variables can be passed by reference to a subroutine to allow the

content of the variable to be updated

AO2: Application

The variables will be stored in memory throughout the whole code execution. However, the amount of data they are storing is relatively low so would not use a lot of memory.
When the game is expanded, the amount of data may increase so it could be memory intensive, especially if graphics are used in the game.
Both arrays are needed throughout the whole game so keeping them as global will make writing the code easier as the programmer will not need to keep passing them as parameters and setting return values.
Only one part of the game is being created initially and therefore the use of global variables would not affect the efficiency greatly. However, when the program expands, it could cause accuracy / testing / debugging and maintenance problems.

AO3: Evaluation

As this is only a prototype, the use of global variables would be beneficial.
However, when the game expands, the use of global variables could create issues such as running out of memory, coupling, testing & debugging problems and maintenance problems.
The programmer may be best to keep the variables as local and then pass them

between the different subroutines as parameters byVal and byRef.

Examiner’s Comments

Most responses were Level 2 for definitions and some expansion to passing parameters. Very few candidates were able to go into depth about alternatives to global variables such as passing by value and passing by reference in detail or extending to issues such as scalability within a larger more extended game. Few candidates picked up on the fact that this was a more limited prototype that was likely to be expanded on which would require more consideration to be given to variable scope.

Your mark for 2(f)

out of 9

Question 3

6 marks

3(a)

A programmer has designed a program that includes a reusable program component.

The reusable program component is a function called isInteger(). This will take a string as an argument and then check that each digit is between 0 and 9. For example if 103 is input, it will check that the digits 1, 0 and 3 are each between 0 and 9.

The asc() function returns the ASCII value of each digit. For example asc("1") returns 49.

The ASCII value for 0 is 48. The ASCII value for 9 is 57.

01   function isInteger(number)
02     result = true
03     for count = 0 to number.length-1
04       asciiValue = asc(number.substring(count, 1))
05         if not(asciiValue >= 48 and asciiValue <= 57) then
06         result = false
07       endif
08     next count
09     return result
10   endfunction

3(a)(i) 1 mark

Identify one identifier used in the function isInteger().

Your answer

Mark scheme 3(a)(i)

Tick each point your answer makes. Your mark is worked out from your ticks, and you can change it.

1 mark for:

• isInteger
• number
• result
• count
• asciiValue

Guidance

Penalise excessive spaces in identifiers such as
ascii Value
instead of asciiValue

Examiner’s Comments

This question was generally well done (although slightly less well done than parts (a) (ii) and (a) (iii)), but many candidates did very well. The most common erroneous responses were giving the names of predefined functions/properties or giving relational operators.

Your mark for 3(a)(i)

out of 1

3(a)(ii) 1 mark

Give the line number where the branching (selection) construct starts in the function isInteger().

Your answer

Mark scheme 3(a)(ii)

(0)5

Guidance

Examiner’s Comments

This question required an exact answer only and was answered correctly by the majority of candidates.

3(a)(iii) 1 mark

Give the line number where the iteration construct starts in the function isInteger().

Your answer

Mark scheme 3(a)(iii)

(0)3

Guidance

Examiner’s Comments

This question also required an exact answer only and was answered correctly by the majority of candidates.

3(b) 3 marks

Describe the purpose of the following lines in the function isInteger().

Line 03

Line 04

Line 09

Your answer

Mark scheme 3(b)

Tick each point your answer makes. Your mark is worked out from your ticks, and you can change it.

1 mark each

03

Loop through each of the characters/digits in the number string (parameter)

04

Find the ASCII value of the current character/digit

09

Return true if the value is an integer and false otherwise

Guidance

Examiner’s Comments

This question required the purpose of the lines of code to be described, but many candidates just described the functionally of the lines of code such as ‘line 03 is a counter controlled loop from 0 to number.length -1’. The expected purpose of this line of code was to set up a loop to iterate through each character in the input string parameter.

While many candidates could describe the purpose of at least one of the lines of code given, few could clearly describe the purpose of all three lines.

Your mark for 3(b)

out of 3

Question 4

5 marks

4 5 marks

A recursive pseudocode function, recursiveAlgorithm(), is shown.

01   function recursiveAlgorithm(value)
02     if value <= 0 then
03       return 1
04     elseif value MOD 2 = 0 then
05       return value + recursiveAlgorithm(value – 3)
06     else
07       return value + recursiveAlgorithm(value – 1)
08     endif
09   endfunction

Trace the recursive function, recursiveAlgorithm(), and give the final return value when called with recursiveAlgorithm(10). You may choose to use the table below to give your answer.

Function call	`value`	`return`

Final return value ……

Your answer

Mark scheme 4

Tick each point your answer makes. Your mark is worked out from your ticks, and you can change it.

1 mark for final return value 29 (award in working or answer space) 1 mark each for working

First call with 10 and second call with 7
Remainder of calls 6, 3, 2
Final call value -1
Adding/showing return values (1 + 2 + 3 + 6 + 7 + 10)

e.g.

Function call	`value`	`return`
`recursiveAlgorithm(10)`	`10`	`29`
`recursiveAlgorithm(7)`	`7`	`19`
`recursiveAlgorithm(6)`	`6`	`12`
`recursiveAlgorithm(3)`	`3`	`6`
`recursiveAlgorithm(2)`	`2`	`3`
`recursiveAlgorithm(–1)`	`–1`	`1`

Guidance

The table is given as guidance, but actual process may be presented in different ways.

Examiner’s Comments

While many candidates continue to find recursion a challenging topic there were many who encouragingly achieved full marks. Weaker candidates traced the initial sequence of calls but found it harder to identify the last call to

recursiveAlgorithm(-1) that

triggered the base case and then found it harder again to calculate the unwind sequence.

Your mark for 4

out of 5

Question 5

2 marks

5(i) 1 mark

The array numbers contains 356 numbers to be sorted by the bubble sort algorithm.

State the maximum number of passes a bubble sort would need to complete to sort 356 numbers into order.

Your answer

Mark scheme 5(i)

355

Guidance

Examiner’s Comments

Many candidates did not appreciate that a bubble sort will require a

maximum of n -1 passes in the worst case since the first item in the list will be in position after that number of passes and so would not require an additional pass. The most common incorrect responses were 356, and 3562 which confused the worst case time complexity O(n²) with the number of passes.

5(ii) 1 mark

State the name of one other sorting algorithm.

Your answer

Mark scheme 5(ii)

Insertion sort

Guidance

Accept any valid sorting algorithm e.g. Merge sort, Quick sort

Examiner’s Comments

Nearly all candidates could identify an additional sorting algorithm with the most common response being ‘Insertion sort’.

Question 6

4 marks

6

Taylor is designing a program for a client who would like to simulate earthquakes on major cities around the world in 3D. The client would like to be able to view any stage of an earthquake such as:

the build-up of the earthquake\
the earthquake taking place\
the aftershocks of the earthquake.
The client would also like to be able to play the simulation at different speeds. For example, a slow, normal or fast speed.

The program will need to accept inputs from the user before playing the simulation.

6(i) 2 marks

Identify two different inputs for this program.

1

2

Your answer

Mark scheme 6(i)

Tick each point your answer makes. Your mark is worked out from your ticks, and you can change it.

1 mark per bullet e.g.

stage (e.g. stage 1, stage 2, stage 3)
city name (e.g. London)
speed (e.g. slow, normal, fast)

Guidance

Examiner’s Comments

Most candidates successfully identified the relevant potential inputs of city/stage/speed from the given scenario. Some candidates suggested alternative inputs such as ‘magnitude of earthquake’ which were also given marks as they were valid inputs for a simulation relating to earthquakes.

Your mark for 6(i)

out of 2

6(ii) 2 marks

One decision point in the program will be to decide if the user inputs are suitable or not.

Identify two other example decision points in this program.

1

2

Your answer

Mark scheme 6(ii)

Tick each point your answer makes. Your mark is worked out from your ticks, and you can change it.

1 mark per bullet to max 2, e.g.

Does the build-up stage need to be shown?
Does the earthquake taking place needs to be shown?
Does the aftershock stage needs to be shown?

Guidance

Allow other suitable examples

Examiner’s Comments

Few candidates were given full marks for this question. There was some repetition of checking user input values, which was given in the stem of the question. There were also many statements of possible calculations rather than clearly expressed conditions or questions. More successful responses included decisions such as ‘have buildings of a certain typ e survived the earthquake?’.

Your mark for 6(ii)

out of 2

Question 7

4 marks

7 4 marks

A program uses a bubble sort to sort data into ascending numerical order.

The data is stored in a 0-indexed 1-dimensional array.

Show each stage of a bubble sort to sort this data into ascending numerical order:

1	5	3	9	2	7

You should clearly show and label each pass in your answer.

Your answer

Mark scheme 7

Tick each point your answer makes. Your mark is worked out from your ticks, and you can change it.

1 mark per bullet

1^st swap of 5 and 3
Remainder of first pass
Pass 2
Pass 3


	1			5		3	9	2	7

1	3	5	9	2	7
1	3	5	2	9	7
1	3	5	2	7	9
1	3	2	5	7	9
1	2	3	5	7	9

End of pass 1

End of pass 2

End of pass 3

Guidance

Candidates do not need to show each swap, so if the candidate has clearly shown the end of pass 1, they have met the first two marking points.

Marks can be awarded for correctly showing the results of each pass.

Examiner’s Comments

Most candidates clearly showed the steps that would take place in a bubble sort for the date given, with most achieving full marks. Some candidates did not explicitly label each pass as required in the question, but marks were given where the passes could be implied.

Few candidates described the principles of a bubble sort instead of applying it to the data given.

Your mark for 7

out of 4

Question 8

5 marks

8(a) 2 marks

Given the following procedure:

01 procedure generate(number)
02      a = 0
03      while number > 0
04         if number MOD 2 == 0 then
05            a = a + 2
06            print(a)
07            number = number – 2
08         else
09            a = a + 1
10            print(a)
11            number = number – 1
12         endif
13      endwhile
14 endprocedure

Explain why = is used on line 11 of the procedure generate instead of ==.

Your answer

Mark scheme 8(a)

Tick each point your answer makes. Your mark is worked out from your ticks, and you can change it.

1 mark per bullet up to a maximum of 2 marks, e.g.:

= is used as the number variable is being assigned a value…
…== is not used as the program is not checking if the variable is equal to a value

Guidance

Accept:

= is an assignment operator
== is a comparison operator.

Examiner’s Comments
Most candidates were correctly able to distinguish between assignment and equality.

Your mark for 8(a)

out of 2

8(b) 1 mark

State the values printed by the procedure generate when number = 7.

Your answer

Mark scheme 8(b)

1,3,5,7

Guidance

Examiner’s Comments
Candidates who answered the previous part of the question generally went on to score full credit for a second trace of the algorithm with a different calling argument value.

8(c) 2 marks

Describe the purpose of the MOD operator on line 04 of the procedure generate.

Your answer

Mark scheme 8(c)

Tick each point your answer makes. Your mark is worked out from your ticks, and you can change it.

1 mark per bullet up to a maximum of 2 marks, e.g.:

Modulo division
Finds the remainder after a division
Used to determine if a is an odd or even number

Guidance

Examiner’s Comments
Candidates who successfully identified that a remainder was calculated found it harder to

determine that its purpose was to see if the number was even or odd.

[An examiner's marking symbol, not shown here.]

Misconception

Some candidates think that a modulo division calculation resulting in 0 means that there is no remainder. Where the result of modulo division is 0 it means that the remainder is 0.

Your mark for 8(c)

out of 2

Question 9

3 marks

9 3 marks

The following pseudocode procedure performs an insertion sort on the array parameter.

01 procedure insertionSort(dataArray:byRef)
02  for i = 1 to dataArray.Length - 1
03    temp = dataArray[i]
04    tempPos = i – 1
05    exit = false
06    while tempPos >= 0 and exit == false
07      if dataArray[tempPos] < temp then
08        dataArray[tempPos + 1] = dataArray[tempPos]
09        tempPos = tempPos - 1
10      else
11        exit = true
12      endif
13    endwhile
14    dataArray[tempPos + 1] = temp
15  next i
16 endprocedure

State whether the procedure insertionSort sorts the data into ascending or descending order and explain your choice.

Your answer

Mark scheme 9

Tick each point your answer makes. Your mark is worked out from your ticks, and you can change it.

1 mark pet bullet to max 3

Descending order
Line 07

(dataArray[tempos]<temp) has

the comparison…

…that checks if current position is less than item to insert and…
…breaks out of loop when current position is less than or equal to item to insert

Your mark for 9

out of 3

Question 10

10 marks

10(a) 9 marks

Poppy would like to use a bubble sort to sort 250 000 numbers into order from lowest to highest.

Currently the first five numbers before they have been sorted are:

195 584	167 147	158 187	160 125	184 236

Currently the last five numbers before they have been sorted are:

1058	19 558	1915	20 215	15

* Discuss how a bubble sort works and how efficient it will be when sorting these 250 000 items into order from lowest to highest.

Your answer

Mark scheme 10(a)

Tick each point your answer makes. Your mark is worked out from your ticks, and you can change it.

Mark Band 3 – High level (7-9 marks) The candidate demonstrates a thorough knowledge and understanding of bubble sorts; the material is generally accurate and detailed. The candidate is able to apply their knowledge and understanding directly and consistently to the context provided. Evidence/examples will be explicitly relevant to the explanation. The candidate is able to weigh up the use of bubble sorts within the context which results in a supported and realistic judgment as to whether it is suitable to use within the context.There is a well- developed line of reasoning which is clear and logically structured. The information presented is relevant and substantiated.

Mark Band 2 – Mid level (4-6 marks) The candidate demonstrates reasonable knowledge and understanding of bubble sorts; the material is generally accurate but at times underdeveloped.The candidate is able to apply their knowledge and understanding directly to the context provided although one

or two opportunities are missed.
Evidence/examples are for the most part implicitly relevant to the explanation. The candidate makes a reasonable attempt to come to a conclusion showing some recognition of influencing factors that would determine whether it is possible to use bubble sorts in this context.
There is a line of reasoning presented with some structure. The information presented is in the most part relevant and supported by some evidence

Mark Band 1 – Low Level (1-3 marks) The candidate demonstrates a basic knowledge of bubble sorts with limited understanding shown; the material is basic and contains some inaccuracies. The candidates makes a limited attempt to apply acquired knowledge and understanding to the context provided. The candidate provides nothing more than an unsupported
assertion.The information is basic and comunicated in an unstructured way. The information is supported by limited evidence and the relationship to the evidence may not be clear.

0 marks
No attempt to answer the question or response is not worthy of credit.

Guidance

Knowledge and Understanding

All adjacent items are compared against each other.
The biggest number in the adjacent pair is swapped over with the smallest number. A temp variable is used to hold the data while it’s being moved.
When a swap is made a flag is set.
This is repeated for all adjacent values, known as one pass.
At the end of one pass, the largest item should appear at the end of the list.
If at the end of the list the flag has been set the flag is unset and the algorithm starts from the beginning of the list again.
When the algorithm gets to the end of the list and the flag is unset the list is sorted.

Application

As there are 250,000 items a bubble sort would perform very slowly as a lot of passes will need to be made in order to sort the items.
Bubble sorts are better suited to data sets where the items are almost/partly sorted. However the smaller numbers are currently towards the end and the larger numbers are towards the start.
This will therefore increase the amount of comparisons / passes/swaps required which will therefore slow the performance of the sort down.

Evaluation

The algorithm is easy to implement as the number of lines of code is less than other standard sorting algorithms.
Although a bubble sort will be able to sort the items into order, it will take longer than other sorting algorithms due to the number of items and the current order or items in the unsorted list.

Your mark for 10(a)

out of 9

10(b) 1 mark

State the number of comparisons that will need to be made in the first pass of the bubble sort.

Your answer

Mark scheme 10(b)

249,999

1 A02.2 (1)

Question 11

32 marks

11(a) 2 marks

A printer buffer is a storage area that holds the data, known as jobs, that are to be printed by a printer.

A simulation of the printer buffer uses a queue data structure to store jobs that are waiting to be printed. The queue is not circular.

The printer buffer is represented as a zero-indexed 1D array with the identifier buffer.

Fig. 2 shows the current contents of the queue buffer and its pointers.

[Diagram redrawn from the original paper by an AI model (Gemma 4 12B). It may contain mistakes.]

Index	Value
6
5
4
3	job-127
2	job-126
1	job-125
0	job-124

queueHead = 0 queueTail = 3

Fig. 2

State the purpose of the pointers queueHead and queueTail.

queueHead

queueTail

Your answer

Mark scheme 11(a)

Tick each point your answer makes. Your mark is worked out from your ticks, and you can change it.

1 mark per pointer

queueHead: Point to the first element in the queue / next element to remove
queueTail: Point to the last element in the queue

Your mark for 11(a)

out of 2

11(b) 5 marks

The function dequeue outputs and removes the next data item in the queue.

The procedure enqueue adds the job passed as a parameter to the queue.

Show the final contents of the queue and pointer values after the following instructions have been run on the queue buffer shown in Fig. 2.

dequeue()

dequeue()

enqueue(job-128)

dequeue()

enqueue(job-129)

[Diagram redrawn from the original paper by an AI model (Gemma 4 12B). It may contain mistakes.]


6
5
4
3
2
1
0

queueHead [ ] queueTail [ ]

Your answer

Mark scheme 11(b)

Tick each point your answer makes. Your mark is worked out from your ticks, and you can change it.

1 mark per bullet up to max 5

first 3 jobs removed
128 and 129 added in positions 4 and 5 respectively
no additional jobs
queueHead being 3 (FT errors)
queueTail being 5 (FT errors)

[Image redrawn from the original mark scheme by an AI model (Gemma 4 12B). It may contain mistakes.]

Index	Value
6
5	job-127
4	job-128
3	job-127
2
1
0

queueHead = 3 queueTail = 5

Guidance

The underlying implementation of the queue has not been specified, so allow alternative valid answers. e.g.
queueHead = 0
queueTail = 2
Location 2: 129
Location 1: 128
Location 0: 127

Your mark for 11(b)

out of 5

11(c)

The array, buffer and pointer values are declared with global scope.

11(c)(i) 5 marks

The function dequeue returns null if the array is empty, and the contents of the next element if not empty. The queue is not circular.

Write an algorithm, using pseudocode or program code, for the function dequeue().

Your answer

Mark scheme 11(c)(i)

Tick each point your answer makes. Your mark is worked out from your ticks, and you can change it.

1 mark per bullet to max 5

Function declaration
Checking if queue is empty
…returning null
(Otherwise) incrementing queueHead
…returning buffer[queueHead-1]

e.g.

function dequeue()
  if queueHead > queueTail then
   return null
  else
   queueHead = queueHead + 1
   return buffer[queueHead-1]
  endif
endfunction

Guidance

Note: Accept alternative valid underlying implementation answers e.g. Shifting all elements in queue forward.

Your mark for 11(c)(i)

out of 5

11(c)(ii) 6 marks

The function enqueue returns -1 if there is no space at the end of the queue to add data, and returns 1 if the parameter was added to buffer. The array buffer contains a maximum of 100 elements.

Write an algorithm, using pseudocode or program code, for the function enqueue().

Your answer

Mark scheme 11(c)(ii)

Tick each point your answer makes. Your mark is worked out from your ticks, and you can change it.

1 mark per bullet to max 6

Function declaration taking parameter
Checking if queue is full
…returning -1
(Otherwise) incrementing queueTail
Adding newJob to buffer(queueTail)
Returning 1

e.g.

function enqueue(newJob)
  if queueTail == 99 then
   return -1
  else
   queueTail = queueTail + 1
   buffer[queueTail] = newJob
   return 1

  endif
endfunction

Your mark for 11(c)(ii)

out of 6

11(c)(iii) 8 marks

In the main program of the simulation the user is asked whether they want to add an item to the queue or remove an item.

If they choose to add an item they have to input the job name, and the function enqueue is called.

If they choose to remove an item, the function dequeue is called and the job name is output.

Appropriate messages are output if either action cannot be run because the queue is either empty or full.

Write, using pseudocode or program code, an algorithm for the main program of the simulation.

Your answer

Mark scheme 11(c)(iii)

Tick each point your answer makes. Your mark is worked out from your ticks, and you can change it.

1 mark per bullet to max 8

Inputting user choice
If enqueue chosen input job name
…call enqueue with input value as parameter
…check if return value is -1 and output full
…otherwise output message that item is added
If dequeue chosen
…call dequeue and save returned value
…output returned value (jobname) if not null
…or output queue is empty

e.g.

main()
  choice = input("Add or remove?")
  if choice == "ADD" then
   jobname = input("Enter job name")
   returnValue = enqueue(jobname)
   if returnValue == -1 then
    print("Queue full")
   else
    print("Job added")
   endif
  else
   returnValue = dequeue()
   if returnValue == null then
    print("Queue empty")
   else
    output returnValue
   endif
  endif
endmain

Guidance

Allow equivalent checks / logic

Your mark for 11(c)(iii)

out of 8

11(d) 3 marks

The queue is changed to make it a circular queue.

Describe how the functions enqueue and dequeue will need to be changed to allow buffer to work as a circular queue.

Your answer

Mark scheme 11(d)

Tick each point your answer makes. Your mark is worked out from your ticks, and you can change it.

1 mark per bullet to 3

Check if either head or tail are incremented to above 99
… set to be 0 instead
When checking if array is full check if (queueTail == queueHead – 1) OR (queueTail==99 AND queueHead==0)

Guidance

Credit equivalent modulo arithmetic solution

Your mark for 11(d)

out of 3

11(e) 3 marks

Some print jobs can have different priorities. The higher the priority the sooner the job needs to be printed.

Describe how the program could be changed to deal with different priorities.

Your answer

Mark scheme 11(e)

Tick each point your answer makes. Your mark is worked out from your ticks, and you can change it.

1 mark per bullet to max 3, e.g.

Use a different structure e.g. a linked list
…items can be added at different points in the linked list depending on priority
…by changing the pointers to items needing priority
Have different queues for different priorities
…add the job to the queue relevant to its priority
…print all the jobs in the highest priority queue first

Guidance

Allow other suitable descriptions that show how the program could be amended.

Your mark for 11(e)

out of 3

Question 12

3 marks

12(a) 1 mark

Given the following procedure:

procedure maths(number)
   a = (number DIV 10) * 10
   b = a + 10
   if (number – a) >= (b – number) then
     print(b)
   else
     print(a)
   endif
endprocedure

State the value printed by the procedure maths if number=10

Your answer

Mark scheme 12(a)

10

1

A03.2 (1)

12(b) 1 mark

State the value printed by the procedure maths if number=27

Your answer

Mark scheme 12(b)

30

1

A03.2 (1)

12(c) 1 mark

State the value printed by the procedure maths if number=14

END OF QUESTION PAPER

Your answer

Mark scheme 12(c)

10

1

A03.2 (1)