Computer Science 9618/13 May/June 2025: question paper and mark scheme
Cambridge AS & A Level Computer Science (9618), Paper 1 Theory Fundamentals, May/June 2025. Read both free below, or download them. Done the paper? Get it marked by AI against this mark scheme.
(a) 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.
(i) Calculate the file size of the image created by the digital camera in megabytes (MB).
Show your working.
Working space ……
Answer …… MB
[2]
(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.
Description Term
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) The student types a report on a computer in a history lesson.
(i) The computer uses the Unicode character set.
Give two characteristics of the Unicode character set.
1 ……
2 ……
[2]
(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.
Character Denary 8-bit Binary Hexadecimal
! 33 21
L 01001100 4C
ü 252 11111100
[3]
Mark scheme
1(a)(i) 1 mark for correct working: 2
e.g.
2000000 * 16 / (8 * 1000 * 1000)
1 mark for answer:
4MB
1(a)(ii) 1 mark each 4
Image:
• There will be fewer shades of colour available
• so the image does not match the original as detail is lost
Image file:
• Fewer bits are used to store each pixel
• so less data is stored, therefore the file size is reduced
1(b) 1 mark for each correct term: 3
Description Sound term
the number of times the amplitude is measured Sampling rate
per time interval
the number of bits used to store each Sampling resolution
amplitude measurement
the type of sound wave before it is recorded by Analogue
a computer
1(c)(i) 1 mark each to max 2 2
• 8 / 16 / 32 / bits per character
• Represents 28 / 216 / etc. characters
• Represents every language and other characters such as emojis
1(c)(ii) 1 mark for each correctly completed space 3
Character Denary 8–bit Binary Hexadecimal
! 33 0010 0001 21
L 76 0100 1100 4C
ü 252 1111 1100 FC
A computer has a processor.
(a) The processor has a Control Unit (CU) and system clock.
(i) Explain how the CU and the system clock work together.
…… [2]
(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]
Mark scheme
2(a)(i) 1 mark each to max 2 - max 1 for each set of marks 2
• The control unit synchronises the actions of the processor
• by sending a command / signal on each timing signal produced by the
system clock
• using / along the control bus
2(a)(ii) 1 mark each 4
• MAR ← [PC] and PC ← [PC] + 1
• MDR ← [[MAR]]
• CIR ← [MDR]
• Correct order
• For example:
• MAR ← [PC]
• PC ← [PC] + 1
• MDR ← [[MAR]]
• CIR ← [MDR]
2(b) 1 mark each 2
• Using cache memory improves system performance
• because cache is fast access memory close to the CPU
• which stores frequently used instructions / data
• so that they can be accessed faster than from RAM
2(c) 1 mark each to max 2 2
e.g.
• HDMI transfers both audio and video using a single cable
• HDMI has a high bandwidth
• Data is transmitted in a stream
• of uncompressed digital signals
• HDMI uses a technology called Transition-Minimized Differential
Signalling (TMDS)
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.
Method How 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]
Mark scheme
3(a) 1 mark for each correctly completed term 4
• an executable file/.exe
• source/program code
• stops
• immediately/in real-time
A compiler checks all of 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
an executable file/.exe which can run without access to the source/program
code.
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 stops and
displays the error. The programmer can correct the error immediately/in real-
time and then the interpreter continues translating from that point.
3(b) 1 mark for method and 1 mark for corresponding description 4
During transmission
e.g.
• Encryption // by example such as VPN
• Jumble / encode data so it cannot be decrypted/understood without the
key
On computer
e.g.
• Firewall / proxy
• Filter incoming transmissions and stop any that could be attempting
unauthorised access
• Anti-malware
• Find and delete or quarantine any malware that could delete the data /
files
• Encryption
• Jumble / encode data so it cannot be decrypted / understood without the
key
• Physical method // by example
• For example, the computer storing the data cannot be accessed without
the key to the room
3(c) 1 mark each to max 4 4
• A webserver stores all the data for each player
• Each player is on a client computer // The player’s web browser is the
client
• that sends requests over the internet to the web server
• the server performs the required action in the game
• the server updates the data in the game
• the server sends the results to the player
3(d) 1 mark each to max 3 3
e.g.
• There is no / limited access to legal advice
• in case action is taken against them
• There are fewer networking opportunities
• so they could miss out on contacts / jobs
• There would be less access to training
• There would be no clear laid out ethical guidelines
• and / or people to discuss potential ethical problems with
• possibly leading to inappropriate / unethical actions
• which might lead to legal proceedings / recourse
(a) Write the logic expressions for the following logic circuit.
A
X
B
C
Y
D
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)
Working space
A B C X
0 0 0
0 0 1
0 1 0
0 1 1
1 0 0
1 0 1
1 1 0
1 1 1
[2]
Mark scheme
4(a) 1 mark for each correct statement 2
X = B NOR (A NOR C)
Y = (B AND C) XOR NOT D
4(b) 1 mark for 1st 4 rows 2
1 mark for 2nd 4 rows
A B C Working space X
0 0 0 1
0 0 1 1
0 1 0 1
0 1 1 0
1 0 0 0
1 0 1 1
1 1 0 1
1 1 1 1
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).
Instruction
Explanation
Opcode Operand
LDM #n Immediate addressing. Load the number n to ACC
STO <address> Store the contents of ACC at the given address
ADD #n/Bn/&n Add 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/&n Subtract 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 #n Compare the contents of ACC with number n
Following a compare instruction, jump to <address> if the compare
JPE <address> was True
END Return 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) The current contents of memory are:
Address Instruction
50 47
51 48
52 49
53 50
...
500 LDM #50
501 DEC ACC
502 CMP 51
503 JPE 505
504 JMP 501
505 STO 50
506 SUB #10
507 STO 51
508 END
(i) Trace the program currently in memory using the following trace table.
Memory address
Instruction address ACC
50 51 52 53
47 48 49 50
[3]
(ii) Complete the table by identifying and describing two modes of addressing that are not used in the program in part (a).
Mode of addressing Description
[4]
(b) The table shows part of the instruction set for a processor. The processor has one register: the Accumulator (ACC).
Instruction
Explanation
Opcode Operand
AND #n/Bn/&n Bitwise AND operation of the contents of ACC with the operand
Bitwise AND operation of the contents of ACC with the contents of
AND <address>
<address>
XOR #n/Bn/&n Bitwise XOR operation of the contents of ACC with the operand
Bitwise XOR operation of the contents of ACC with the contents of
XOR <address>
<address>
OR #n/Bn/&n Bitwise OR operation of the contents of ACC with the operand
Bitwise OR operation of the contents of ACC with the contents of
OR <address>
<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]
Mark scheme
5(a)(i) 1 mark for each shaded section 3
Instruction Memory address
address ACC
50 51 52 53
47 48 49 50
500 50
501 49
502
504
501 48
502
503
505 48
506 38
507 38
5(a)(ii) 1 mark for addressing mode, 1 mark for matching description 4
• Direct
• The operand is the address of the data
• Indirect
• The operand points to the memory location which is the address of the
data
• Indexed
• The address of the data is formed by adding the contents of the Index
Register (IX) to the operand
5(b) 1 mark for each correct instruction 2
e.g.
AND B00000000 / #0 / &0
OR B10000000 / #128 / &80
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.
CUSTOMER ORDER
SUPPLIER ORDER_PRODUCT
PRODUCT
(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:
CustomerName NotCollected
Jack Wright 2
Lin Cho 1
Santaya Yui 1
…… [4]
(d) The shop uses a Database Management System (DBMS).
(i) 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]
(ii) The DBMS provides a developer interface.
Explain how a database designer can make use of the developer interface.
…… [3]
Mark scheme
6(a) 1 mark for each correct relationship 4
CUSTOMER ORDER
ORDER_PRODUCT
SUPPLIER
PRODUCT
6(b) 1 mark each 4
• INSERT INTO PRODUCT
• VALUES with opening and closing brackets
• Inserting ProductID, ProductName and SupplierID correctly as strings
including quotation marks into correct fields
• Inserting quantity and cost correctly into correct fields
Example 1:
INSERT INTO PRODUCT
VALUES ("002323", "Blue ball point 2 mm", 50, 5.00, "SFX223");
Example 2:
INSERT INTO PRODUCT (ProductID, ProductName, QuantityInBox, Cost,
SupplierID)
VALUES ("002323", "Blue ball point 2 mm", 50, 5.00, "SFX223");
6(c) 1 mark each 4
• Selection of customer name and counting any field from ORDER as an
appropriate identifier
• Joining tables ORDER and CUSTOMER
• AND (or WHERE) clause: Collected = FALSE
• Grouping by customer ID or customer name
Example 1:
SELECT CustomerName, COUNT(OrderID) AS NotCollected
FROM ORDER, CUSTOMER
WHERE ORDER.CustomerID = CUSTOMER.CustomerID
AND Collected = FALSE
GROUP BY CUSTOMER.CustomerID
Example 2:
SELECT CustomerName, COUNT(OrderID) AS NotCollected
FROM ORDER INNER JOIN CUSTOMER
ON ORDER.CustomerID = CUSTOMER.CustomerID
WHERE Collected = FALSE
GROUP BY CUSTOMER.CustomerID
6(d)(i) 1 mark each to max 3 3
e.g.
• Relationships
• Views
• Data types
• Validation rules
6(d)(ii) 1 mark each to max 3 3
e.g.
• To create / modify / delete database objects
• To create a form for data input
• To add tools to a form
• for example, drop-down boxes / buttons etc.
• To design a report to show the output in an organised manner
• To add a menu to enable users to choose different actions / run different
queries
(a) A computer can perform logical and arithmetic shifts.
(i) Show the result of a logical left shift of 2 places on the two’s complement binary integer
11001010
…… [1]
(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).
1 1 1 1 0 1 0 1
+ 1 0 1 1 0 0 0 1
[1]
(c) Subtract the binary number 00011110 from the binary number 01100100 using binary subtraction. Show your working.
[2]
Examiners follow the generic marking principles at the front of the scheme, then each question's points: method (M), accuracy (A) and independent (B) marks, error carried forward where the scheme allows it, and positive marking, so you're credited for what you got right.
Check your answers against it
Done this paper? Upload your script and CIE Buddy's AI marker marks it question by question against this exact scheme, puts the ticks on your own working and says what each lost mark needed.
Where can I find the 9618/13 May/June 2025 mark scheme?+
On this page, free: the mark scheme for AS & A Level Computer Science 9618/13, May/June 2025 (9618_s25_ms_13), and the question paper (9618_s25_qp_13), to read or download, with each question's marking points written out underneath.
How many marks is 9618/13 out of?+
Computer Science 9618/13 for May/June 2025 is out of 75 marks, with 1 hour 30 minutes to answer it.
Can I get my 9618/13 answers marked?+
Yes. Upload your answers to 9618/13/M/J/25 as a PDF or photos, and CIE Buddy marks every question against this paper's official mark scheme, using Cambridge's marking rules. You get your score, each lost mark explained on your own script, and the topics to revise. It's a guide, not an official Cambridge grade.