AS Level Computer Science H046/02 Algorithms and problem solving June 2020

Oxford Cambridge and RSA

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Friday 27 May 2022 – Morning

AS Level Computer Science

H046/02 Algorithms and problem solving

Time allowed: 1 hour 15 minutes

INSTRUCTIONS

• Use black ink.

• Write your answer to each question in the space provided. If you need extra space use

the lined pages at the end of this booklet. The question numbers must be clearly shown.

• Answer all the questions.

INFORMATION

• The total mark for this paper is 70.

• The marks for each question are shown in brackets [ ].

• Quality of extended response will be assessed in questions marked with an asterisk (*).

• This document has 16 pages.

ADVICE

• Read each question carefully before you start your answer.

DC (ST/CGW) 300547/6

*8322620926*

*H04602*

Do not use:

• a calculator

2

Answer all the questions.

1 Ruhail owns ten different function rooms which can be hired by different business customers to

hold meetings. He would like a program to manage the booking process of each room.

Customers should be able to enter the date they want to hire a function room, and then a list

of available rooms will be displayed. Customers can then select which room they want to hire.

Customers can then enter their payment details which are then checked and then a confirmation

email is sent to the customer.

(a) Complete the structure diagram below to show the different component parts of the problem.

Function

rooms

Choose

room

Check

payment details

Check

payment

Check

availability

[4]

(b) Ruhail will make use of an Integrated Development Environment (IDE).

State the purpose of an IDE.

...................................................................................................................................................

.............................................................................................................................................. [1]

(c) State two different programming constructs and give an example of how Ruhail could use

each construct when creating his program code.

1 ................................................................................................................................................

...................................................................................................................................................

2 ................................................................................................................................................

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[4]

3

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(d) Ruhail will test his program code to make sure that it works correctly.

State two test strategies that Ruhail could use.

1 ................................................................................................................................................

...................................................................................................................................................

2 ................................................................................................................................................

...................................................................................................................................................

[2]

(e) Ruhail will make use of a software development life cycle methodology.

State two software development methodologies that Ruhail could consider using.

1 ................................................................................................................................................

...................................................................................................................................................

2 ................................................................................................................................................

...................................................................................................................................................

[2]

(f) Ruhail has been told to make use of reusable components when creating his program code.

Explain two benefits of using reusable components when writing program code.

1 ................................................................................................................................................

...................................................................................................................................................

2 ................................................................................................................................................

...................................................................................................................................................

[4]

4

2 Logan is writing a program for his customers to be able to buy his gym equipment. In the program,

once a customer has selected the items they want to buy, a procedure, checkDetails, will be

called. This procedure will check that the customer has input their telephone number and also

check that it is at least 11 characters long.

(a) Logan has written two possible versions of the procedure that could be used to achieve this.

Version One:

procedure checkDetails()

telephoneNo = input("Enter telephone number")

while (telephoneNo == "") or (telephoneNo.length < 11)

print("Error, please try again")

telephoneNo = input("Enter telephone number")

endwhile

endprocedure

Version Two:

procedure checkDetails()

telephoneNo = input("Enter telephone number")

if (telephoneNo == "") or (telephoneNo.length < 11) then

print("Error, please try again")

telephoneNo = input("Enter telephone number")

endif

endprocedure

(i) Explain why version one is more effective than version two at making sure that the

telephone number entered is at least 11 characters long.

...........................................................................................................................................

...................................................................................................................................... [4]

5

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(ii) As well as the procedure checkDetails, Logan would like to use additional procedures

to expand his program.

The program will be expanded to:

• allow customers to be able to register an account by setting up a username and

password

• allow registered users to be able to log-in with their registration details

• allow customers, once logged in, to be able to add items that are in stock to their

online shopping basket.

State two other procedures that Logan could write to meet these requirements, and for

each one, state a suitable name and purpose.

Procedure 1:

Procedure Name: ..............................................................................................................

Purpose: ............................................................................................................................

...........................................................................................................................................

Procedure 2:

Procedure Name: ..............................................................................................................

Purpose: ............................................................................................................................

...........................................................................................................................................

[4]

(iii) When setting up the additional procedures in his program, Logan will use a mixture of

parameter passing by reference and by value.

State the difference between parameter passing by reference and parameter passing by

value.

...........................................................................................................................................

...................................................................................................................................... [2]

6

(b)* Logan will work in a team with five other programmers and together they will create the

programming code for the program.

Discuss how modularity can be used to allow the team of programmers to work effectively

together on the same program at the same time.

...................................................................................................................................................

.............................................................................................................................................. [9]

7

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3 Trudi would like to sort an array of numbers into order.

The numbers before they have been sorted can be seen here.

89 25 75 37 45

(a) Trudi will use a bubble sort to put these numbers into order from smallest to largest.

Show the first pass of the bubble sort. You should clearly show each comparison made.

...................................................................................................................................................

.............................................................................................................................................. [4]

8

(b) Trudi has written a procedure, bubbleSort.

01 procedure bubbleSort(numbers)

02 do

03 sorted = true

04 for count = 0 to numbers.length -2

05 if numbers[count] > numbers[count+1] then

06 temp = numbers[count+1]

07 numbers[count+1] = numbers[count]

08 numbers[count] = temp

09 sorted = false

10 endif

11 next count

12 until sorted == true

13 endprocedure

(i) Identify a line in the procedure bubbleSort where a decision is taken.

...........................................................................................................................................

...................................................................................................................................... [1]

(ii) Identify the name of the parameter used in the procedure bubbleSort.

...........................................................................................................................................

...................................................................................................................................... [1]

(iii) Describe the purpose of the temp variable in the procedure bubbleSort.

...........................................................................................................................................

...................................................................................................................................... [2]

(iv) Describe the purpose of the sorted variable in the procedure bubbleSort.

...........................................................................................................................................

...................................................................................................................................... [2]

9

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4 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

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

...................................................................................................................................................

.............................................................................................................................................. [2]

(b) State the values printed by the procedure generate when number = 8.

...................................................................................................................................................

.............................................................................................................................................. [1]

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

...................................................................................................................................................

.............................................................................................................................................. [1]

10

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

...................................................................................................................................................

.............................................................................................................................................. [2]

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5 A veterinary surgery uses a two dimensional array to store bookings for customers to bring in their

animal to see the vet. There are ten possible booking slots during each day.

An example of the two dimensional array is shown in Fig. 1.

• The first column stores the booking slot number, ranging between 1 and 10.

• The second column stores the time of the appointment.

• The third column stores the customerID of the customer who has booked that slot.

1 9:00 5877RC

2 9:30 9655AS

3 10:00

4 10:30 8754TT

5 11:00

6 11:30 8745SD

7 13:00 9635GH

8 13:30

9 14:00 9874PL

10 14:30 9658SV

Fig. 1

If a customerID has been entered for a booking slot then the booking slot has been taken. If no

customerID has been entered then the booking slot is available for booking.

(a) When customers make an appointment they often ask for the first available booking slot.

Describe how a linear search could be used for this purpose.

...................................................................................................................................................

.............................................................................................................................................. [3]

12

(b) A function findFirst, is used to find the first available appointment.

Write the function findFirst that will find the first available appointment and return the

booking slot number. If no appointments are available then the function should return "-1".

You should write your function using pseudocode or program code.

...................................................................................................................................................

.............................................................................................................................................. [7]

(c) When an available time slot has been found then a valid customerID must be entered to

confirm the booking.

This is checked by another function called checkCustomerID. This will return true if the

customerID is valid or false if the customerID is not valid.

State why a function would be used instead of a procedure for this purpose.

...................................................................................................................................................

.............................................................................................................................................. [1]

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6 Kylie buys used games consoles and then sells them to make a profit. She sells her products in

multiples of £5 such as £30, £55 and £95. Kylie only accepts £50, £20, £10 and £5 notes from her

customers.

Kylie has written an algorithm which will calculate the amount of change needed by stating how

many £20, £10 and £5 notes are needed.

The program should output the minimum number of notes required. For example if £35 change is

required then it should output 1 x £20 and 1 x £10 and 1 x £5.

01 total = input("Enter total price of goods")

02 paid = input("Enter amount paid”)

03 global change = paid – total

04 calculateChange()

05

06 procedure calculateChange()

07 twenty = 0

08 ten = 0

09 five = 0

10 while change >= 20 //Calculates number of £20 notes needed

11 twenty = twenty + 1

12 change = change – 20

13 endwhile

14 while change >= 10 //Calculates number of £10 notes needed

15 ten = ten + 1

16 change = change – 10

17 endwhile

18 while change >= 5 //Calculates number of £5 notes needed

19 five = five + 1

20 change = change – 5

21 endwhile

22 print("The amount of change you need is £" + str(change))

23 print("Total £20 Notes:" + str(twenty))

24 print("Total £10 Notes:" + str(ten))

25 print("Total £5 Notes:" + str(five))

26 endprocedure

(a) Describe how calculateChange() on line 04 is used differently to calculateChange()

on line 06.

...................................................................................................................................................

.............................................................................................................................................. [2]

14

(b) When line 22 is run, it will always print:

The amount of change you need is £0

Explain why this error occurs when line 22 is run.

...................................................................................................................................................

.............................................................................................................................................. [2]

(c) Explain why Kylie has used str on lines 22 to 25 in her algorithm.

...................................................................................................................................................

.............................................................................................................................................. [3]

END OF QUESTION PAPER

15

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