Computer Science 9618/13 May/June 2024: question paper and mark scheme
Cambridge AS & A Level Computer Science (9618), Paper 1 Theory Fundamentals, May/June 2024. Read both free below, or download them. Done the paper? Get it marked by AI against this mark scheme.
(a) Complete the following description.
A kibibyte has a …… prefix. Three kibibytes is the same
as …… bytes.
A megabyte has a …… prefix. Two terabytes is the same
as …… gigabytes.
[4]
(b) Convert the denary number 241 to hexadecimal.
…… [1]
(c) State what is meant by an overflow in binary addition.
…… [1]
(d) Computers use character sets when representing characters in binary.
(i) Complete the table by identifying the number of bits each of the character sets allocates to each character.
Character set Number of bits
ASCII
extended ASCII
Unicode
[1]
(ii) Explain how the word ‘Clock’ is represented by a character set.
…… [2]
Mark scheme
1(a) 1 mark for each correct answer: 4
binary
3072
denary/decimal
2000
A kibibyte has a binary prefix. Three kibibytes is the same as 3072 bytes.
A megabyte has a decimal/denary prefix. Two terabytes is the same as 2000
gigabytes.
1(b) 1 mark for correct answer: 1
F1
1(c) 1 mark for a correct answer: 1
The answer is too long to be represented in the same number of bits as the
binary numbers being added
1(d)(i) 1 mark for all 3 answers correct: 1
Character set Number of bits
ASCII 7
extended ASCII 8
Unicode 16/32
1(d)(ii) 1 mark each: 2
Each character has a unique binary code
The binary code for each character is stored in sequence
A photograph is stored as a bitmap image.
(a) The photograph has a resolution of 4000 pixels wide by 3000 pixels high. The bit depth is
4 bytes.
Calculate an estimate for the file size of the photograph in megabytes.
Show your working.
Working ……
Answer …… megabytes
[2]
(b) The photograph is compressed before being uploaded to a web server.
(i) Give three benefits of this photograph being compressed using lossy compression instead of lossless compression.
1 ……
2 ……
3 ……
[3]
(ii) Explain how run-length encoding (RLE) will compress the photograph.
…… [2]
(c) Identify two elements of a bitmap image that can be changed to reduce its file size.
1 ……
2 ……
[2]
Mark scheme
2(a) 1 mark for working: 2
4000 * 3000 * 4
1 mark for correct answer:
48MB
2(b)(i) 1 mark each to max 3: 3
The file takes less storage space on the web server than if lossless
compression was used
The file is faster to upload/download to/from the server than if lossless
compression was used
The file uses less bandwidth to transmit than if lossless compression was
used
The file consumes less data allowance than if lossless compression was
used
2(b)(ii) 1 mark each: 2
Identifies consecutive repeating pixels of the same colour
Stores the colour /pattern and the number of times it repeats
2(c) 1 mark each to max 2: 2
Colour/bit depth
Image resolution
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
Direct addressing. Load the contents of the location at the given
LDD <address> address to ACC
Indirect addressing. The address to be used is at the given address.
LDI <address>
Load the contents of this second address to ACC
Indexed addressing. Form the address from <address> + the contents
LDX <address> of the index register. Copy the contents of this calculated address to
ACC
LDR #n Immediate addressing. Load the number n to IX
ADD #n/Bn/&n Add the number n to the ACC
ADD <address> Add the contents of the given address to the ACC
DEC <register> Subtract 1 from the contents of the register (ACC or IX)
SUB #n/Bn/&n Subtract the number n from the ACC
SUB <address> Subtract the contents of the given address from the ACC
INC <register> Add 1 to the contents of the register (ACC or IX)
<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 shown:
Address Data
48 51
49 6
50 48
51 50
52 49
53 50
54 6
The current contents of the ACC and IX are shown:
ACC 2
IX 50
Complete the table by writing the content of the ACC after each program has run.
Program number Code ACC content
LDM #50
1 INC ACC
SUB #1
LDI 51
2
ADD 52
LDR #2
LDX 50
3
DEC ACC
LDD 52
4 SUB 54
INC ACC
[4]
(b) The processor includes these bit manipulation instructions:
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>
Bits in ACC are shifted logically n places to the left. Zeros are
LSL #n introduced on the right-hand end
Bits in ACC are shifted logically n places to the right. Zeros are
LSR #n introduced on the left-hand end
<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
The current contents of memory are shown:
Address Data
100 00001101
101 10111110
102 11110011
103 00110111
104 00000000
The current content of the ACC is shown:
1 1 1 1 1 1 1 1
Complete the table by writing the content of the ACC after each instruction has run.
The binary number 11111111 is reloaded into the ACC before each instruction is run.
Instruction number Instruction ACC content
1 LSL #2
2 XOR 100
3 AND 103
[3]
Mark scheme
3(a) 1 mark for each correct answer: 4
Program Code ACC
Number Content
1 LDM #50 50
INC ACC
SUB #1
2 LDI 51 97
ADD 52
3 LDR #2 48
LDX 50
DEC ACC
4 LDD 52 44
SUB 54
INC ACC
3(b) 1 mark for each correct answer: 3
Instruction Instruction ACC Content
Number
1 LSL #2 1111 1100
2 XOR 100 1111 0010
3 AND 103 0011 0111
A theatre wants to use a database to store data about the shows that are scheduled, their customers and the seats that the customers have booked.
In the theatre:
• Each show can take place on multiple dates.
• Some dates can have more than one performance.
• There are multiple rows of seats.
• Each seat can be individually booked by its row letter and seat number, for example row E seat 2.
Part of the database design includes these tables:
SHOW(ShowID, Title, Duration)
SEAT(SeatID, RowLetter, SeatNumber)
PERFORMANCE(PerformanceID, ShowID, ShowDate, StartTime)
(a) Identify the relationship between the tables PERFORMANCE and SHOW.
…… [1]
(b) Sample data for the table PERFORMANCE is shown:
PerformanceID ShowID ShowDate StartTime
0001 MK12 5/5/2025 13:00
0002 MK12 5/5/2025 19:30
0003 MK12 6/5/2025 19:00
0004 OP3 7/5/2025 18:30
0005 OP3 8/5/2025 18:30
0006 OP3 9/5/2025 13:00
Write a Structured Query Language (SQL) script to define the table PERFORMANCE.
…… [4]
(c) Write an SQL script to return the number of times each show is scheduled. For example, in the sample data in part (b), the show MK12 is scheduled three times.
The result needs to include the show name and a suitable field name for the number of times it is scheduled.
…… [4]
(d) Customers give their first name, last name and email address when they are making a
booking. One booking can include multiple seats.
Describe the additional tables that will need to be included in the database and explain how these tables will be linked within the database.
…… [5]
Mark scheme
4(a) 1 mark for: 1
many to 1 // there are many performances of each show
4(b) 1 mark each for: 4
Creating table PERFORMANCE with opening and closing brackets
Setting all four attributes with appropriate data types
Setting PerformanceID as primary key
Setting ShowID as foreign key referencing SHOW table
Example:
CREATE TABLE PERFORMANCE(
PerformanceID varchar NOT NULL,
ShowID varchar,
ShowDate Date,
StartTime Time,
PRIMARY KEY(PerformanceID),
FOREIGN KEY(ShowID) REFERENCES SHOW(ShowID)
);
4(c) 1 mark each for: 4
Selecting COUNT of an attribute in PERFORMANCE table with suitable name
FROM clause
Joining tables
Grouping by the title and selecting the title
Example 1:
SELECT SHOW.Title, Count(PERFORMANCE.PerformanceID)
AS NumberOfShowings
FROM PERFORMANCE, SHOW
WHERE PERFORMANCE.ShowID = SHOW.ShowID
GROUP BY SHOW.Title;
Example 2:
SELECT SHOW.Title, Count(PERFORMANCE.PerformanceID)
AS NumberOfShowings
FROM PERFORMANCE INNER JOIN SHOW
ON PERFORMANCE.ShowID = SHOW.ShowID
GROUP BY SHOW.Title;
4(d) 1 mark each to max 5: 5
e.g.
CUSTOMER table identified with suitable Primary Key and appropriate
name
… and other suitable fields including name and email
BOOKING TABLE identified with suitable Primary Key and appropriate
name
… that stores the Primary Key of the CUSTOMER table as a Foreign Key
to join with CUSTOMER table
… and stores the Primary Key of the PERFORMANCE table as a Foreign
Key to join with PERFORMANCE table
A linking table between Table 2 and SEAT with suitable Primary Key and
appropriate name
… that includes the Primary Key of Table 2 as a Foreign Key to join with
Table 2
… that stores the SeatID.
A multimedia design company has an office with a LAN (local area network). The LAN can have up to 20 devices connected with cables and other devices connected using wireless access.
(a) The company has private cloud storage for its employees to store their work.
(i) Define the term private cloud.
…… [1]
(ii) Describe the benefits to the company of using private cloud storage instead of public cloud storage.
…… [3]
(b) Part of the internal structure of the wired LAN is a star topology.
Explain how packets are transmitted between two devices in a star topology.
…… [2]
(c) A different part of the network uses the Ethernet protocol.
(i) A collision is detected.
Describe how the collision is managed using Carrier Sense Multiple Access/Collision
Detection (CSMA/CD).
…… [2]
(ii) Identify two drawbacks of using CSMA/CD.
1 ……
2 ……
[2]
(d) The devices in the office have static private IP addresses.
State what is meant by a static private IP address.
…… [1]
Mark scheme
5(a)(i) 1 mark for: 1
Dedicated/bespoke services/storage on a remote server only available to
company
5(a)(ii) 1 mark each to max 3: 3
e.g.
Not reliant on a third party
… gives greater control over security/privacy
… gives greater control over backup
Storage can be tailored/scalable to company requirements// an example
e.g. the amount of storage accessible/ facilitating the sharing of files
5(b) 1 mark each: 2
Sending computer transmits packets directly to switch/router/central
device
Switch/router/central device checks destination address of packet and
forwards directly to that device
5(c)(i) 1 mark each to max 2: 2
Jamming signal is transmitted by the sending device
Transmission is aborted
The sending device waits a random time before trying to send data
again ...
... if further collisions occur the wait time is increased
5(c)(ii) 1 mark each to max 2: 2
Random time increased each time so can be infinite waiting
May be constant jamming signal so nothing ever sends
Certain nodes cannot be prioritised
High power consumption
Only suitable for short distance network // limited distance
Not scalable // more nodes means exponentially longer waiting times
5(d) 1 mark for: 1
Static means the IP for that device does not change and Private means it can
only be accessed/seen/used within the LAN
Each of the following truth tables has three inputs (A, B and C) and one output (X).
Draw one line to match each truth table with its logic expression.
Truth table Logic expression
A B C X
0 0 0 0 NOT (A XOR B) AND C
0 0 1 1
0 1 0 0
0 1 1 0
1 0 0 1
1 0 1 1
1 1 0 0
(A OR C) AND NOT B
1 1 1 0
A B C X
0 0 0 0
0 0 1 1
0 1 0 0
0 1 1 0 A NAND B NAND C
1 0 0 0
1 0 1 0
1 1 0 0
1 1 1 1
A B C X
(A NAND B) OR C
0 0 0 1
0 0 1 1
0 1 0 1
0 1 1 1
1 0 0 1
1 0 1 1
NOT (A AND B AND C)
1 1 0 0
1 1 1 1
[3]
Robots are used to serve food and drink to customers at a restaurant.
(a) A robot navigates through the restaurant to the table it is serving.
Complete the table by identifying two sensors that can be included in the robot and the purpose of each sensor in the navigation system.
Sensor Purpose of sensor in navigation system
[2]
(b) The robot uses Artificial Intelligence (AI) to communicate with the customers. The customers speak to the robot to order their food and drinks.
Explain how AI will be used in this part of the robot.
…… [3]
(c) The navigation system can be considered an example of a control system.
Describe how feedback is used in a control system.
…… [2]
(d) The robot includes a touchscreen for the customer to make their payment.
Describe the principal operation of a touchscreen.
…… [4]
(e) Program libraries were used when writing the robot’s software.
(i) State what is meant by a program library.
…… [1]
(ii) Some program libraries include Dynamic Link Library (DLL) files.
Describe the benefits of a programmer using a library with DLL files instead of using a
library that does not include DLL files.
…… [4]
(f) The data from the robots is transmitted to a central computer using a wireless connection.
(i) Complete the table by identifying and describing two methods of data verification that can be used during data transfer.
Method Description
1
2
[4]
(ii) Explain how encryption can protect the security of data during transmission.
…… [2]
Mark scheme
7(a) 1 mark for sensor and matching purpose to max 2: 2
Sensor Purpose of sensor in navigation system
Pressure To detect if a table or other obstacle has been hit // to detect
when food is put on/taken off the tray so it can move on
Infra-red To detect if there is an obstacle in the way // to indicate that it
has reached the desired table
Sound To detect if someone is speaking so that it can use AI to
decipher the speech and whether the robot is required to stop
7(b) 1 mark each to max 3: 3
e.g.
Voice/speech recognition is used
... to identify if someone speaking
The sound is recorded and analysed
The audio recordings are compared to a database of words/sound waves
... to identify the word that has the highest probability of being said
Natural language recognition is used
Words are combined and compared to known sentences
… programmed action(s) for matching sentence(s) are performed
7(c) 1 mark each to max 2: 2
Feedback ensures that a system operates within set criteria / constraints
... by enabling system output to affect subsequent system input
... thus allowing conditions to be automatically adjusted
7(d) 1 mark each to max 4: 4
Resistive: The space between the conductive layers is removed/the
layers touch and a circuit is completed
Capacitive: The electrical charge changes where the user pressed
The point of contact is identified
... from the change in electrical field
The software/microprocessor calculates the coordinates
7(e)(i) 1 mark for: 1
Pre-written code/functions/routines that can be imported/called in another
program
7(e)(ii) 1 mark each to max 4: 4
Maintenance not needed to be done by the programmer
... because the DLL is separate from program
The calling program does not need recompilation by the programmer when
a DLL file changes
... because the DLL file can be updated independently of the calling
program
… updates will apply to all programs that use the DLL file
7(f)(i) 1 mark for each correct method and 4
1 mark for corresponding description to max 4:
Method Description
Parity byte An additional bit is added to make the number of 1s in the
byte odd or even to match the parity. If a byte with an odd
number of 1 bits is received when even parity is used, there is
an error.
Parity block Parity is calculated horizontally and vertically. A parity byte is
created from the bits produced by the vertical parity check.
This is sent with the data. The parity is re-checked when
received and the position of an incorrect bit can be
determined.
Checksum A calculation is made from the data and the result transmitted
with the data. The receiver repeats the calculation and
compares the result with the value received. If the two are
different, there is an error.
7(f)(ii) 1 mark each to max 2: 2
Encodes/scrambles data
... so if it is intercepted it cannot be understood
Algorithm/key is required to decode the data
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On this page, free: the mark scheme for AS & A Level Computer Science 9618/13, May/June 2024 (9618_s24_ms_13), and the question paper (9618_s24_qp_13), to read or download, with each question's marking points written out underneath.
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Computer Science 9618/13 for May/June 2024 is out of 75 marks, with 1 hour 30 minutes to answer it.
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