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A Level Computer Science 9618 Paper 13, May/June 2025

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9618/13 · May/June 2025

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1
a(i)

A student paints a picture in an art class. The student takes a photograph of the picture using a digital camera. The digital camera creates an image with a resolution of 2 million pixels and uses a bit depth of 16 bits. Calculate the file size of the image created by the digital camera in megabytes (MB). Show your working. Working space ................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... Answer ...................................... MB

[2]
a(ii)

The student takes a second photograph with a lower bit depth. Explain the effect of decreasing the bit depth on the image and on the image file. Effect on image ................................................................................................................. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... Effect on image file ............................................................................................................ ........................................................................................................................................... ........................................................................................................................................... ...........................................................................................................................................

[4]
b

A teacher records an audio file of the student playing the piano during a music lesson. Complete the table by giving the term for each description about sound representation on a computer.

DescriptionTerm
the number of times the amplitude is
measured per time interval
the number of bits used to store each
amplitude measurement
the type of sound wave before it is recorded
by a computer
[3]
c(i)

The student types a report on a computer in a history lesson. The computer uses the Unicode character set. Give two characteristics of the Unicode character set. 1 ........................................................................................................................................ ........................................................................................................................................... 2 ........................................................................................................................................ ...........................................................................................................................................

[2]
c(ii)

Some of the school's computers use the extended ASCII character set. The table gives some characters from the extended ASCII character set, their denary, 8-bit binary and hexadecimal numbers. Complete the table by filling in the missing numbers.

CharacterDenary8-bit BinaryHexadecimal
!3321
L010011004C
ü25211111100
[3]
2

A computer has a processor.

a(i)

The processor has a Control Unit (CU) and system clock. Explain how the CU and the system clock work together.

[2]
a(ii)

The processor runs the Fetch-Execute (F-E) cycle. Write the stages of the F-E cycle using register transfer notation.

[4]
b

The computer has cache memory. Describe one benefit of the computer using cache memory.

[2]
c

The computer connects to a monitor using a High Definition Multimedia Interface (HDMI) cable that connects into an HDMI port. Explain how HDMI provides connection to peripheral devices.

[2]
3

A programmer is writing a program in a high-level language.

a

Complete the description of compilers and interpreters by writing the missing words. A compiler checks all the code before attempting to translate the program. If any errors are found, they are all reported at the same time and the program does not translate or run. If there are no errors found, the compiler produces ........................................................ which can run without access to the ........................................................ . An interpreter translates one line of code and then runs it, before moving to the next line of code. If the line of code has an error, the interpreter ........................................................ and displays the error. The programmer can correct the error ........................................................ and then the interpreter continues translating from that point.

[4]
b

The programmer needs to keep the program files secure on their computer and during electronic data transmission over the internet. The files are protected by a password. Complete the table by identifying one other method of keeping the files secure during electronic data transmission and one other method of keeping the files secure on the computer. State how each method protects the data. The methods must be different.

MethodHow the method protects the data
during transmission.................................................................................................................
.................................................................................................................
...........................................................................
on the computer.................................................................................................................
.................................................................................................................
...........................................................................
[4]
c

The computer program allows users to play a game in a virtual world. Users can play the game from any computer with internet access using a web browser. The game allows users to interact with other users. Explain the reasons why the statement ‘This computer game uses a client-server model’ is correct.

[4]
d

Describe the possible consequences of the programmer not joining a professional ethical body.

[3]
4
Figure 1 of 1 for question 4
a

Write the logic expressions for the following logic circuit. X = ............................................................................................................................................ Y = ............................................................................................................................................

[2]
b

Complete the truth table for the logic expression: X=(A OR B) XOR (B OR C) XOR (NOT A NAND C)

ABCWorking spaceX
000
001
010
011
100
101
110
111
[2]
5

The following table shows part of the instruction set for a processor. The processor has two registers: the Accumulator (ACC) and an Index Register (IX).

InstructionExplanation
OpcodeOperand
LDM#nImmediate addressing. Load the number n to ACC
STO<address>Store the contents of ACC at the given address
ADD#n/Bn/&nAdd the number n to the ACC
ADD<address>Add the contents of the given address to the ACC
SUB<address>Subtract the contents of the given address from the ACC
SUB#n/Bn/&nSubtract the number n from the ACC
DEC<register>Subtract 1 from the contents of the register (ACC or IX)
JMP<address>Jump to the given address
CMP<address>Compare the contents of ACC with the contents of <address>
CMP#nCompare the contents of ACC with number n
JPE<address>Following a compare instruction, jump to <address> if the compare was True
ENDReturn control to the operating system

ACC denotes Accumulator <address> can be an absolute or a symbolic address # denotes a denary number, e.g. #123 B denotes a binary number, e.g. B01001010 & denotes a hexadecimal number, e.g. &4A

a(i)

The current contents of memory are:

AddressInstruction
5047
5148
5249
5350
...
500LDM #50
501DEC ACC
502CMP 51
503JPE 505
504JMP 501
505STO 50
506SUB #10
507STO 51
508END

Trace the program currently in memory using the following trace table.

Instruction addressACCMemory address
50515253
47484950
[3]
a(ii)

Complete the table by identifying and describing two modes of addressing that are not used in the program in part (a).

Mode of addressingDescription
...................................................................................................................................
...................................................................................................................................
................................................................................
................................................................................
...................................................................................................................................
...................................................................................................................................
................................................................................
................................................................................
[4]
b

The table shows part of the instruction set for a processor. The processor has one register: the Accumulator (ACC).

InstructionExplanation
OpcodeOperand
AND#n/Bn/&nBitwise AND operation of the contents of ACC with the operand
AND<address>Bitwise AND operation of the contents of ACC with the contents of <address>
XOR#n/Bn/&nBitwise XOR operation of the contents of ACC with the operand
XOR<address>Bitwise XOR operation of the contents of ACC with the contents of <address>
OR#n/Bn/&nBitwise OR operation of the contents of ACC with the operand
OR<address>Bitwise OR operation of the contents of ACC with the contents of <address>

<address> can be an absolute or a symbolic address # denotes a denary number, e.g. #123 B denotes a binary number, e.g. B01001010 & denotes a hexadecimal number, e.g. &4A Write the bit manipulation instructions that can be used to set only the most significant bit to 1 in an 8-bit register. The instructions need to work on a register that contains any 8-bit binary number.

[2]
6

A shop sells pens to customers. Customers place an order with the shop and collect the items the next day. The shop uses a database to store the information about the orders. The database contains the following tables: CUSTOMER(CustomerID, CustomerName, Email) ORDER(OrderID, CustomerID, Date, Collected) ORDER_PRODUCT(OrderID, ProductID, Quantity) PRODUCT(ProductID, ProductName, QuantityInBox, Cost, SupplierID) SUPPLIER(SupplierID, SupplierName, SupplierEmail) The primary keys are underlined.

a

Complete the entity-relationship (E-R) diagram for the database.

[4]
b

A new product needs to be entered into the database. The product has the ID 002323, the product name ‘Blue ball point 2mm’, there are 50 in a box, the product costs $5.00 and the supplier has the ID SFX223. Write a Structured Query Language (SQL) script to enter the new product into the table PRODUCT.

[4]
c

The attribute Collected in the table ORDER stores the Boolean value TRUE if the order has been collected and FALSE if the order has not been collected. Write an SQL script to return the customer name for each customer that has orders they have not collected. Include the number of orders each customer has not collected with an appropriate title. An example output might be:

CustomerNameNotCollected
Jack Wright2
Lin Cho1
Santaya Yui1
[4]
d(i)

The shop uses a Database Management System (DBMS). One feature provided by a DBMS is a data dictionary. The data dictionary stores the attribute names, table names, foreign keys and primary keys in the database. Identify three other items stored in a data dictionary. 1 ........................................................................................................................................ 2 ........................................................................................................................................ 3 ........................................................................................................................................

[3]
d(ii)

The DBMS provides a developer interface. Explain how a database designer can make use of the developer interface.

[3]
7

A computer can perform logical and arithmetic shifts.

a(i)

Show the result of a logical left shift of 2 places on the two's complement binary integer 11001010

[1]
a(ii)

Show the result of an arithmetic right shift of 3 places on the two's complement binary integer 10011110

[1]
b

Complete the following binary addition. Show your working. Include any overflow bit(s).

11110101
+10110001
[1]
c

Subtract the binary number 00011110 from the binary number 01100100 using binary subtraction. Show your working.

[2]

Mark scheme

9618/13 · May/June 2025

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1a(i) · 2 marks

  • 1 mark

    Correct working: e.g. 2000000 * 16 / (8 * 1000 * 1000)

  • 1 mark

    Answer: 4MB

1a(ii) · 4 marks

  • 1 mark

    Image: There will be fewer shades of colour available

  • 1 mark

    Image: so the image does not match the original as detail is lost

  • 1 mark

    Image file: Fewer bits are used to store each pixel

  • 1 mark

    Image file: so less data is stored, therefore the file size is reduced

1b · 3 marks

  • 1 mark

    Sampling rate

  • 1 mark

    Sampling resolution

  • 1 mark

    Analogue

1c(i) · 2 marks

  • 1 mark

    8 / 16 / 32 / bits per character

  • 1 mark

    Represents 2^8 / 2^16 / etc. characters

  • 1 mark

    Represents every language and other characters such as emojis

1c(ii) · 3 marks

  • 1 mark

    Correctly completed row for '!': Denary 33, Binary 0010 0001, Hexadecimal 21

  • 1 mark

    Correctly completed row for 'L': Denary 76, Binary 0100 1100, Hexadecimal 4C

  • 1 mark

    Correctly completed row for 'ü': Denary 252, Binary 1111 1100, Hexadecimal FC

2a(i) · 2 marks

  • 1 mark

    The control unit synchronises the actions of the processor

  • 1 mark

    by sending a command / signal on each timing signal produced by the system clock

  • 1 mark

    using / along the control bus

2a(ii) · 4 marks

  • 1 mark

    MAR ← [PC] and PC ← [PC] + 1

  • 1 mark

    MDR ← [[MAR]]

  • 1 mark

    CIR ← [MDR]

  • 1 mark

    Correct order

2b · 2 marks

  • 1 mark

    Using cache memory improves system performance

  • 1 mark

    because cache is fast access memory close to the CPU

  • 1 mark

    which stores frequently used instructions / data

  • 1 mark

    so that they can be accessed faster than from RAM

2c · 2 marks

  • 1 mark

    HDMI transfers both audio and video using a single cable

  • 1 mark

    HDMI has a high bandwidth

  • 1 mark

    Data is transmitted in a stream

  • 1 mark

    of uncompressed digital signals

  • 1 mark

    HDMI uses a technology called Transition-Minimized Differential Signalling (TMDS)

3a · 4 marks

  • 1 mark

    an executable file/.exe

  • 1 mark

    source/program code

  • 1 mark

    stops

  • 1 mark

    immediately/in real-time

3b · 4 marks

  • 1 mark

    During transmission method: Encryption // by example such as VPN

  • 1 mark

    During transmission description: Jumble / encode data so it cannot be decrypted/understood without the key

  • 1 mark

    On computer method: Firewall / proxy // Anti-malware // Encryption // Physical method // by example

  • 1 mark

    On computer corresponding description: Filter incoming transmissions and stop any that could be attempting unauthorised access // Find and delete or quarantine any malware that could delete the data / files // Jumble / encode data so it cannot be decrypted / understood without the key // For example, the computer storing the data cannot be accessed without the key to the room

3c · 4 marks

  • 1 mark

    A webserver stores all the data for each player

  • 1 mark

    Each player is on a client computer // The player’s web browser is the client

  • 1 mark

    that sends requests over the internet to the web server

  • 1 mark

    the server performs the required action in the game

  • 1 mark

    the server updates the data in the game

  • 1 mark

    the server sends the results to the player

3d · 3 marks

  • 1 mark

    There is no / limited access to legal advice

  • 1 mark

    in case action is taken against them

  • 1 mark

    There are fewer networking opportunities

  • 1 mark

    so they could miss out on contacts / jobs

  • 1 mark

    There would be less access to training

  • 1 mark

    There would be no clear laid out ethical guidelines

  • 1 mark

    and / or people to discuss potential ethical problems with

  • 1 mark

    possibly leading to inappropriate / unethical actions

  • 1 mark

    which might lead to legal proceedings / recourse

4a · 2 marks

  • 1 mark

    X = B NOR (A NOR C)

  • 1 mark

    Y = (B AND C) XOR NOT D

4b · 2 marks

  • 1 mark

    1st 4 rows (1, 1, 1, 0)

  • 1 mark

    2nd 4 rows (0, 1, 1, 1)

5a(i) · 3 marks

  • 1 mark

    First section (rows for initial loop / 500-504)

  • 1 mark

    Second shaded section (rows 501-505)

  • 1 mark

    Third section (rows 506-507)

5a(ii) · 4 marks

  • 1 mark

    Direct: The operand is the address of the data

  • 1 mark

    Indirect: The operand points to the memory location which is the address of the data

  • 1 mark

    Indexed: The address of the data is formed by adding the contents of the Index Register (IX) to the operand

  • 1 mark

    Correct identification/matching of addressing modes and descriptions

5b · 2 marks

  • 1 mark

    AND B00000000 / #0 / &0

  • 1 mark

    OR B10000000 / #128 / &80

6a · 4 marks

  • 1 mark

    CUSTOMER to ORDER (1 to many)

  • 1 mark

    ORDER to ORDER_PRODUCT (1 to many)

  • 1 mark

    PRODUCT to ORDER_PRODUCT (1 to many)

  • 1 mark

    SUPPLIER to PRODUCT (1 to many)

6b · 4 marks

  • 1 mark

    INSERT INTO PRODUCT

  • 1 mark

    VALUES with opening and closing brackets

  • 1 mark

    Inserting ProductID, ProductName and SupplierID correctly as strings including quotation marks into correct fields

  • 1 mark

    Inserting quantity and cost correctly into correct fields

6c · 4 marks

  • 1 mark

    Selection of customer name and counting any field from ORDER as an appropriate identifier

  • 1 mark

    Joining tables ORDER and CUSTOMER

  • 1 mark

    AND (or WHERE) clause: Collected = FALSE

  • 1 mark

    Grouping by customer ID or customer name

6d(i) · 3 marks

  • 1 mark

    Relationships

  • 1 mark

    Views

  • 1 mark

    Data types

  • 1 mark

    Validation rules

6d(ii) · 3 marks

  • 1 mark

    To create / modify / delete database objects

  • 1 mark

    To create a form for data input

  • 1 mark

    To add tools to a form

  • 1 mark

    for example, drop-down boxes / buttons etc.

  • 1 mark

    To design a report to show the output in an organised manner

  • 1 mark

    To add a menu to enable users to choose different actions / run different queries

7a(i) · 1 mark

  • 1 mark

    0010 1000

7a(ii) · 1 mark

  • 1 mark

    1111 0011

7b · 1 mark

  • 1 mark

    (1) 1010 0110

7c · 2 marks

  • 1 mark

    showing binary subtraction (any method)

  • 1 mark

    answer 0100 0110

Questions

  1. 1
    Question 114 marks
    Mark scheme ›
  2. 2
    Question 210 marks
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  3. 3
    Question 315 marks
    Mark scheme ›
  4. 4
    Question 44 marks
    Mark scheme ›
  5. 5
    Question 59 marks
    Mark scheme ›
  6. 6
    Question 618 marks
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  7. 7
    Question 75 marks
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