Computer Science 9618/12 October/November 2022: question paper and mark scheme
Cambridge AS & A Level Computer Science (9618), Paper 1 Theory Fundamentals, October/November 2022. Read both free below, or download them. Done the paper? Get it marked by AI against this mark scheme.
(a) Draw one line from each utility software to its most appropriate purpose.
Utility software Purpose
to reorganise files so they are contiguous virus checker to scan for malicious program code disk formatter
to decrease the file size
backup
to initialise a disk
disk repair to create copies of files in case the original is lost defragmentation to check for and fix inconsistencies on a disk
[5]
(b) Compilers and interpreters translate programs written in a high-level language into a low-level language.
(i) State two drawbacks of using a compiler compared to an interpreter during program development.
1 ……
2 ……
[2]
(ii) Explain why high-level language programs might be partially compiled and partially interpreted.
…… [2]
Mark scheme
1(a) 1 mark for each correct line. 5
Utility software Purpose
to reorganise files so
virus checker they are contiguous
to scan for malicious
program code
disk formatter
to decrease the file size
backup
to initialise a disk
disk repair to create copies of files
in case the original is
lost
to check for and fix
defragmentation inconsistencies on a
disk
1(b)(i) 1 mark for each bullet point (max 2): 2
• larger amounts of source code take time to compile
• slower to produce the object code than an interpreter
• code cannot be changed without recompilation
• the program will not run if there are any errors
• errors cannot be corrected in real-time
• one error may result in other false errors being reported
• cannot easily test specific sections of the source code // cannot easily test
unfinished source code
1(b)(ii) 1 mark for each bullet point (max 2): 2
• partially compiled programs can be used on different platforms as they
are interpreted when run
• code is optimised for the CPU as machine code is generated at run time
(a) A greenhouse has an automatic window.
The window (X) operates according to the following criteria:
Parameter Description of parameter Binary value Condition
1 Too high
T Temperature
0 Acceptable
1 Too high
W Wind speed
0 Acceptable
1 Detected
R Rain
0 Not detected
1 On
M Manual override
0 Off
The window opens (X = 1) if:
• the temperature is too high and the wind speed is acceptable
• and
• rain is not detected, or the manual override is off.
Draw a logic circuit to represent the operation of the window.
T
W
X
R
M
[3]
(b) Complete the truth table for the logic expression:
X = NOT (A OR B OR C) AND (B NOR 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]
(c) Embedded systems contain Read Only Memory (ROM) and Random Access Memory (RAM).
Explain the reasons why ROM is used in an embedded system.
…… [2]
Mark scheme
3(a) 1 mark for T AND NOT W 3
1 mark for NOT R OR NOT M
1 mark for final AND
X
3(b) 1 mark for each set of rows as highlighted: 2
A B C X
0 0 0 1
0 0 1 0
0 1 0 0
0 1 1 0
1 0 0 0
1 0 1 0
1 1 0 0
1 1 1 0
3(c) 1 mark for each bullet point: 2
• to store data that does not change
• data must be stored even when device is without power
• to store boot up instructions / system software / firmware / BIOS
(a) State the difference between data verification and data validation.
…… [1]
(b) A checksum can be used to detect errors during data transmission.
Describe how a checksum is used.
…… [3]
(c) One validation method is a presence check.
Describe two other validation methods that can be used to validate non-numeric data.
1 ……
2 ……
[2]
Mark scheme
4(a) data verification is checking if input data is the same as the original whereas 1
data validation is checking that the data is reasonable / sensible
4(b) 1 mark for each bullet point (max 3): 3
• checksum value is calculated from the data before transmission //
correct description of a checksum algorithm
• ... this calculated value is transmitted with the data
• receiving computer recalculates the checksum from the received data
• if the checksum received and calculated match, no error has occurred //
if the checksum received and calculated do not match, an error has
occurred
4(c) 1 mark for each bullet point (max 2). 2
For example:
• to make sure data is in the required format // only expected characters
allowed
• to make sure the data is already present in the system
• to make sure the data contains the correct number of characters
• to ensure that non-numeric data is entered
A relational database, GARDEN, has the following tables:
OWNER(OwnerID, FirstName, TelephoneNo, TreeID, TreePosition)
TREE(TreeID, ScientificName, MaxHeight, FastGrowing)
(a) The database is not in Third Normal Form (3NF).
Explain how the database can be normalised to 3NF.
…… [3]
(b) Write the Structured Query Language (SQL) script to add a new record in the table TREE to store the following data:
Attribute Value
TreeID LOW_1276
ScientificName Salix_Alba
MaxHeight 30.00
FastGrowing TRUE
…… [3]
(c) State what is meant by a candidate key in a relational database.
…… [1]
(d) (i) Describe, using an example, what is meant by a data dictionary.
…… [2]
(ii) Describe what is meant by a logical schema.
…… [2]
Mark scheme
5(a) 1 mark for each bullet point (max 3): 3
Solution 1:
• removing the many-to-many relationship between Owner and Tree
• ... by removing TreeID and TreePosition from the Owner table
• ... and creating a linking table between Owner and Tree
• ... that contains OwnerID, TreeID and TreePosition
• ... (composite) primary key of the linking table should be OwnerID and
TreeID // insert a named new primary key in the linking table
Solution 2:
• removing the many-to-many relationship between Owner and Tree
• move TreePosition into TREE table
• ... put OwnerID into TREE table
• create a new table with suitable name (for the species of tree)
• ... containing ScientificName, MaxHeight and FastGrowing
• ... with ScientificName as primary key // or another suitable primary key
5(b) 1 mark for each bullet point: 3
• INSERT INTO TREE
• VALUES ( ) and correct values
• Values in correct order
Option 1:
INSERT INTO
TREE(TreeID, ScientificName, MaxHeight, FastGrowing)
VALUES('LOW_1276', 'Salix_Alba', 30.00, TRUE);
Option 2:
INSERT INTO
TREE
VALUES('LOW_1276', 'Salix_Alba', 30.00, TRUE);
5(c) 1 mark for: 1
An attribute / field (or set of attributes / fields) that could be a primary key
5(d)(i) 1 mark for description 2
• stores metadata about the database
1 mark for a correct example
For example:
• field / attribute names
• table name
• validation rules
• data types
• primary keys // foreign keys
• relationships
5(d)(ii) 1 mark for each bullet point (max 2): 2
• the overview of a database structure
• models the problem / situation
• ... by using methods such as an ER diagram
• independent of any particular DBMS
(a) A student uses a networked laptop computer to send an email to a colleague.
(i) Explain how a digital signature ensures the email is authentic.
…… [2]
(ii) Describe how a firewall protects the data on the computer.
…… [3]
(b) The student records a sound file.
(i) Explain the effect of increasing the sampling rate on the accuracy of the sound recording.
…… [2]
(ii) Explain the effect of decreasing the sampling resolution on the file size of the sound recording.
…… [2]
Mark scheme
6(a)(i) 1 mark for each method of ensuring authenticity (max 2): 2
• (email) message put through hashing algorithm to produce a digest
• Digest encrypted with sender’s private key (to create the digital signature)
• the (digital) signature can only be decrypted with matching sender’s
public key
6(a)(ii) 1 mark for each bullet point: 3
• monitors incoming and outgoing packets / traffic
• checks against an allow list / deny list of IP addresses // checks against
a set of rules for acceptable data / ports etc.
• blocks transmissions that do not meet criteria / rules // allows through is
satisfies the criteria /rules
6(b)(i) 1 mark for each bullet point (max 2): 2
• improves the accuracy of the sound file
• ... because (digital) waveform more closely resembles the analogue
waveform
• quantization errors are reduced
• increases the amount of detail stored
6(b)(ii) 1 mark for each bullet point: 2
• decreases the file size of the sound file
• ... because fewer bits are used to store each sample
The following table shows part of the instruction set for a processor. The processor has one general purpose register, the Accumulator (ACC), and an Index Register (IX).
Instruction
Explanation
Opcode Operand
LDM #n Immediate addressing. Load the number n to ACC
LDD <address> Direct addressing. Load the contents of the location at the given address to
ACC
LDX <address> Indexed addressing. Form the address from <address> + the contents of the index register. Copy the contents of this calculated address to ACC
LDR #n Immediate addressing. Load the number n to IX
STO <address> Store the contents of ACC at the given address
ADD <address> Add the contents of the given address to the ACC
ADD #n Add the denary number n to the ACC
INC <register> Add 1 to 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>
CMI <address> Indirect addressing. The address to be used is at the given address. Compare the contents of ACC with the contents of this second address
JPE <address> Following a compare instruction, jump to <address> if the compare was True
JPN <address> Following a compare instruction, jump to <address> if the compare was False
END Return control to the operating system
<address> can be an absolute or symbolic address
# denotes a denary number, e.g. #123
B denotes a binary number, e.g. B01001101
(a) Trace the program currently in memory using the trace table, stopping when line 90 is executed for a second time.
Address Instruction Instruction Memory address
ACC IX address 100 101 102 103 110 111 112
75 LDR #0
LDX 110 0 0 112 4 1 4 0
76
77 CMI 102
78 JPE 91
79 CMP 103
80 JPN 84
81 ADD 101
82 STO 101
83 JMP 86
84 INC ACC
85 STO 101
86 LDD 100
87 INC ACC
88 STO 100
89 INC IX
90 JMP 76
91 END
100 0
101 0
102 112
103 4
110 1
111 4
112 0
[5]
(b) The following table shows another part of the instruction set for the processor.
Instruction
Explanation
Opcode Operand
AND #n Bitwise 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 Bitwise XOR operation of the contents of ACC with the operand
XOR Bn Bitwise XOR operation of the contents of ACC with the binary number n
XOR <address> Bitwise XOR operation of the contents of ACC with the contents of <address>
OR #n Bitwise 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>
LSL #n Bits in ACC are shifted logically n places to the left. Zeros are introduced on the right-hand end
LSR #n Bits in ACC are shifted logically n places to the right. Zeros are introduced on the left-hand end
<address> can be an absolute or symbolic address
# denotes a denary number, e.g. #123
B denotes a binary number, e.g. B01001101
The contents of memory addresses 50 and 51 are shown:
Memory address Data value
50 01001101
51 10001111
(i) The current contents of the ACC are:
0 1 0 1 0 0 1 1
Show the contents of the ACC after the execution of the following instruction.
XOR B00011111
[1]
(ii) The current contents of the ACC are:
0 1 0 1 0 0 1 1
Show the contents of the ACC after the execution of the following instruction.
AND 50
[1]
(iii) The current contents of the ACC are:
0 1 0 1 0 0 1 1
Show the contents of the ACC after the execution of the following instruction.
LSL #3
[1]
(iv) The current contents of the ACC are:
0 1 0 1 0 0 1 1
Show the contents of the ACC after the execution of the following instruction.
OR 51
[1]
(c) Write the register transfer notation for each of the stages in the fetch-execute cycle described in the table.
Description Register transfer notation
Copy the address of the next instruction into the Memory Address Register.
Increment the Program Counter.
Copy the contents of the Memory Data
Register into the Current Instruction Register.
[3]
Mark scheme
7(a) 1 mark for each set of highlighted rows. 5
Instruction Memory address
ACC IX
address 100 101 102 103 110 111 112
0 0 112 4 1 4 0
75 0
76 1
77
78
79
80
84 2
85 2
86 0
87 1
88 1
89 1
90
76 4
77
78
79
80
81 6
82 6
83
86 1
87 2
88 2
89 2
90
7(b)(i) 0100 1100 1
7(b)(ii) 0100 0001 1
7(b)(iii) 1001 1000 1
7(b)(iv) 1101 1111 1
7(c) 1 mark for each correct row: 3
Description Register transfer notation
Copy the address of the next instruction into
MAR [PC]
the Memory Address Register.
Increment the Program Counter. PC [PC] + 1
Copy the contents of the Memory Data
CIR [MDR]
Register into the Current Instruction Register.
The following bitmap image has a resolution of 4096 × 4096 pixels and a colour depth of 24 bits per pixel.
The image is displayed on a monitor that has a screen resolution of 1920 × 1080 pixels.
(a) Tick (3) one box in each row to identify the effect of each action on the image file size.
Increases the Decreases the No change to
Action file size file size the file size
Change the colour depth of the image file to 16 bits per pixel.
Change the screen resolution to 1366 × 768 pixels.
Change the colour of the rectangle from black to red.
[2]
(b) State two benefits of creating a vector graphic instead of a bitmap image.
1 ……
2 ……
[2]
(c) A second bitmap image is stored using a colour depth of 8 bits per pixel.
The file is compressed using run-length encoding (RLE).
(i) The table shows the compressed and uncompressed values for parts of the image file.
Each colour of the pixel in the image is represented by a hexadecimal value.
Complete the table. The first row has been completed for you.
Uncompressed image RLE compressed image
EA F1 F1 F2 F2 F2 EA 1EA 2F1 3F2 1EA
2AB 2FF 11D 167
32 32 80 81 81
[2]
(ii) RLE is an example of lossless compression.
Explain why lossless compression is more appropriate than lossy compression for a text file.
…… [2]
Mark scheme
8(a) 1 mark one or two correct row(s). 2 marks for all three correct rows. 2
Increases Decreases No change to
Action
the file size the file size the file size
Change the colour depth of
the image file to 16 bits per ✓
pixel.
Change the screen resolution
✓
to 1366 × 768 pixels.
Change the colour of the
✓
rectangle from black to red.
8(b) 1 mark for each bullet point (max 2). 2
For example:
• can be enlarged without pixelation / loss of quality
• individual components of the image can be edited
• generally a smaller file size
8(c)(i) 1 mark for each correct underlined part: 2
Uncompressed sound RLE compressed sound
EA F1 F1 F2 F2 F2 EA 1EA 2F1 3F2 1EA
AB AB FF FF 1D 67 2AB 2FF 11D 167
32 32 80 81 81 232 180 281
8(c)(ii) 1 mark for each bullet point: 2
• all the data is required // no data can be lost
• ... otherwise text file will be corrupted / not make sense
One use of Artificial Intelligence (AI) is for facial recognition software.
Describe the social impact of using facial recognition software to identify individuals in an airport.
…… [2]
Mark scheme
9 1 mark for each bullet point (max 2). 2
For example:
• incorrect recognition of faces leads to mistakes such as
• ... access to facilities / systems may be denied
• privacy issues / people do not like data being stored
• individuals will feel safer
• ... there might be a reduction in crime
• faster boarding
• catching criminals
A Local Area Network (LAN) consists of four computers, one server and a switch.
The LAN uses a star topology.
(a) Complete the following diagram to show how the hardware is connected.
Switch
Computer Computer Server Computer Computer
[1]
(b) A router is attached to one of the devices on the LAN shown in part (a) to connect the LAN to the internet.
(i) Identify the device. Give a reason for your choice.
Device ……
Reason ……
[2]
(ii) Describe the role and function of the router in the network.
…… [3]
Mark scheme
10(a) all four computers directly connected to the switch and no other connections. 1
10(b)(i) 1 mark for the device. 1 mark for corresponding reason. 2
• Device: Server
• Reason: Server processes the requests and authorises traffic // firewall
software on the server authorises traffic // server acts as the proxy
• Device: Switch
• Reason: Switch is connected to all the computers // to share access to
the router on the network
10(b)(ii) 1 mark for each bullet point (max 3): 3
• receive packets from devices / internet
• find destination of packets using the IP address
• forward packets to the destination
• assign private IP addresses to devices on LAN
• store/update/maintain a routing table
• find most efficient path to destination
• maintain table of MAC and IP addresses
• provides the LAN with a public IP address
• acts as a gateway
• performs protocol conversion
• acts as a firewall
Checked your answers against these? Let AI mark the whole paper, on your own working.
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 9618/12 October/November 2022 mark scheme?+
On this page, free: the mark scheme for AS & A Level Computer Science 9618/12, October/November 2022 (9618_w22_ms_12), and the question paper (9618_w22_qp_12), to read or download, with each question's marking points written out underneath.
How many marks is 9618/12 out of?+
Computer Science 9618/12 for October/November 2022 is out of 75 marks, with 1 hour 30 minutes to answer it.
Can I get my 9618/12 answers marked?+
Yes. Upload your answers to 9618/12/O/N/22 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.