Computer Science 9618/13 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 digital audio message needs to be recorded.
(a) Tick () one box in each row to identify the effect of each action on the accuracy of the recording.
Accuracy Accuracy Accuracy does
Action increases decreases not change
Change the sampling rate from 40 kHz to 60 kHz.
Change the duration of the recording from 20 minutes to 40 minutes.
Change the sampling resolution from
24 bits to 16 bits.
[2]
(b) The audio message is recorded with a sampling rate of 50 kHz and a sampling resolution of
16 bits.
The recording is 20 minutes in length.
Calculate the file size of the recording.
Give your answer in megabytes and show your working.
Working ……
Answer …… megabytes
[2]
(c) A computer uses a buffer when playing the audio message.
Explain the purpose of a buffer in a computer system using one other example.
…… [3]
Mark scheme
1(a) 1 mark for one or two correct ticks, 2 marks for three correct ticks. 2
Accuracy Accuracy Accuracy
Action increases decreases does not
change
Change the sampling rate from
✓
40 kHz to 60 kHz.
Change the duration of the
recording from 20 minutes to 40 ✓
minutes.
Change the sampling resolution
✓
from 24 bits to 16 bits.
1(b) 1 mark for answer; 1 mark for working. 2
Working:
Size = 50KHz * (20 × 60) * 16 bits
= 50 000 * 1200 * 16 bits // 50 000 *1200 * 2 bytes
= 960 000 000 bits
= 120 000 000 bytes
= 120 000 kilobytes
= 120 megabytes
Answer = 120 megabytes
1(c) 1 mark for purpose (max 2): 3
Purpose:
• to act as temporary storage // to store (downloaded) data
• ... before it is used by the receiving device
• ... to allow processes / devices to operate at different speeds //
independently of each other
1 mark for each example (max 1):
Examples:
• printer buffer used when data is transferred from a computer to a printer
• video buffer when streaming videos
• keyboard buffer when performing data entry
The relational database ASTRONOMY is used to store data about telescopes, the companies that own the telescopes and the photographs taken by the telescopes.
The database has these three tables:
COMPANY(TelephoneNumber, CompanyID, CompanyName)
PHOTOGRAPH(PhotoID, TelescopeID, DateTaken, TimeTaken, Elevation)
TELESCOPE(TelescopeID, CompanyID, SerialNumber)
(a) Complete the following table by writing the correct answer for each item.
Item Answer
a suitable field for the primary key in
COMPANY
a candidate key in TELESCOPE
the degree of relationship between
TELESCOPE and PHOTOGRAPH
[3]
(b) A Database Management System (DBMS) has several features.
Identify the feature that describes the relationship between data and its structure.
…… [1]
(c) Complete the SQL script to return the total number of telescopes owned by the company whose ID begins with HW.
SELECT …… (……)
FROM TELESCOPE
WHERE …… LIKE ……;
[4]
(d) Write the SQL script to add one field to the table PHOTOGRAPH to store the resolution of the photograph, e.g. 1920 × 1068.
…… [2]
(e) The photographs are stored as bitmap images.
Complete the statements about bitmap images by writing the missing words.
The …… of a bitmap image is the number of
bits that are used to store each pixel.
Metadata about the image is stored in the ……
of the file.
[2]
(f) Describe the purpose of a query processor in a DBMS.
…… [2]
Mark scheme
2(a) 1 mark for each correct answer. 3
Item Answer
a suitable field for the primary key in COMPANY CompanyID
SerialNumber //
a candidate key in TELESCOPE
TelescopeID
the degree of relationship between TELESCOPE 1:M / 1 to many
and PHOTOGRAPH
2(b) Logical schema 1
2(c) 1 mark for each correctly completed missing part: 4
SELECT COUNT (TelescopeID)
FROM TELESCOPE
WHERE CompanyID LIKE 'HW%';
2(d) 1 mark for each bullet point: 2
• ALTER TABLE PHOTOGRAPH
• ADD Resolution TEXT;
ALTER TABLE PHOTOGRAPH
ADD Resolution TEXT / VARCHAR(11);
2(e) 1 mark for each correctly completed term; 2
The bit depth of a bitmap image is the number of bits that are used to store
each pixel.
Metadata about the image is stored in the header of the file.
2(f) 1 mark for each bullet point (max 2): 2
• allows the user to enter criteria
• searches for the data that meets the entered criteria
• organises the results to be displayed to the user
Draw one line from each Operating System (OS) management task to its most appropriate description.
OS Management task Description
dynamically allocates memory to processes
hardware management
marks unallocated file storage for availability
security management
installs programs for devices connected to external ports
memory management
validates user and process authenticity
process management
allows processes to transfer data to and from each other
[4]
Mark scheme
3 1 mark for each correct line: 4
OS Management task Description
dynamically allocates
memory to processes
hardware
management
marks unallocated file
storage
for availability
security management
installs programs for
devices connected to
external ports
memory management
validates user and
process authenticity
process management
allows processes to transfer
data to and from each other
(a) A Central Processing Unit (CPU) contains several special purpose registers and other components.
(i) State the roles of the following registers.
Memory Address Register (MAR) ……
Memory Data Register (MDR) ……
[2]
(ii) State when interrupts are detected during the Fetch-Execute (F-E) cycle.
…… [1]
(b) A computer system contains a system clock.
Describe the purpose of the system clock.
…… [2]
(c) Upgrading secondary storage to solid state typically improves the performance of computer systems.
Identify one other upgrade to the hardware and explain why it improves the performance of a computer system.
Upgrade ……
Explanation ……
[2]
Mark scheme
4(a)(i) 1 mark for each register: 2
MAR:
• holds address in memory from which data will be read / to which data will
be written
MDR:
• holds the data/instructions which has been read from or is to be written
to the address in the MAR
4(a)(ii) after completion of the execute stage // before the cycle begins 1
4(b) 1 mark for each bullet point (max 2): 2
• synchronise operations
• ... by creating timing signals
• to keep track of the date and time / timestamp files
• to process operations in the correct order / sequence
4(c) 1 mark for identification of a correct upgrade: 2
1 mark for a corresponding explanation:
Examples:
• increase quantity of RAM
• ... so allowing more applications to reside in memory at the same time,
saving disk access times
• increase the size of cache memory
• ... so that the CPU can continue working without waiting for data
• increase clock speed
• ... so that more instructions are performed in a time period
• increase the number of processors / cores
• ... so that more instructions are performed in parallel
(a) Draw a logic circuit for the logic expression:
X = NOT ((NOT (A AND B)) OR (NOT (B AND C)))
A
B X
C
[3]
(b) Complete the truth table for the logic expression:
Y = (NOT P AND Q) OR (Q AND NOT R)
Working space
P Q R Y
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]
Question 6 begins on page 10.
Mark scheme
5(a) 1 mark for each bullet point: 3
• NOT (A AND B)
• NOT (B AND C)
• NOT(NOT(A AND B) OR NOT(B AND C))
5(b) 1 mark for each set of highlighted rows. 2
P Q R Y
0 0 0 0
0 0 1 0
0 1 0 1
0 1 1 1
1 0 0 0
1 0 1 0
1 1 0 1
1 1 1 0
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
MOV <register> Moves the contents of the accumulator to the given register (IX)
STO <address> Store 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
SUB #n Subtract the denary number n from the ACC
INC <register> Add 1 to the contents of the register (ACC or IX)
JMP <address> Jump to the given address
CMP #n Compare the contents of ACC with number n
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
OUT Output to the screen the character whose ASCII value is stored in
ACC
END Return control to the operating system
<address> can be an absolute or a symbolic address
# denotes a denary number, e.g. #123
B denotes a binary number, e.g. B01001101
(a) The current contents of main memory and selected values from the ASCII character set are given.
(i) Trace the program currently in memory using the trace table.
Instruction Memory address
Address Instruction ACC IX Output
LDR #0 address 100 101 110 111 112
75
76 LDD 100
1 0 97 98 97
77 CMP #2
78 JPE 91
79 LDX 110
80 SUB #32
81 CMP #65
82 JPN 86
83 LDM #1
84 ADD 101
85 STO 101
86 LDM #1
87 ADD 100
88 STO 100
89 INC IX
90 JMP 76
91 LDD 101
92 ADD #48
93 OUT
94 END
100 1
101 0
110 97
111 98
112 97
ASCII Character value
49 1
50 2
51 3
52 4
65 A
66 B
67 C
68 D
[4]
(ii) Explain the purpose of relative addressing in an assembly language program.
…… [2]
(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 Bn Bitwise AND operation of the contents of ACC with the binary number n
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 <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 Bn Bitwise OR operation of the contents of ACC with the binary number n
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 a symbolic address
# denotes a denary number, e.g. #123
B denotes a binary number, e.g. B01001101
(i) The current contents of the ACC are:
0 0 1 1 0 1 1 0
Show the contents of the ACC after the execution of the following instruction.
AND B01001100
[1]
(ii) The current contents of the ACC are:
1 0 0 1 0 1 0 1
Show the contents of the ACC after the execution of the following instruction.
OR B01001111
[1]
(iii) The current contents of the ACC are:
1 0 0 1 1 1 0 1
Show the contents of the ACC after the execution of the following instruction.
LSR #2
[1]
(c) One instruction group is data movement.
Give the name of one other instruction group.
…… [1]
Mark scheme
6(a)(i) 1 mark for each set of highlighted rows: 4
Instruction Memory address Output
ACC IX
address 100 101 110 111 112
1 0 97 98 97
75 0
76 1
77
78
79 97
80 65
81
82
83 1
84
85 1
86
87 2
88 2
89 1
90
76
77
78
91 1
92 49
93 1
94
6(a)(ii) 1 mark for each bullet point: 2
• To allow for re-locatable code
• ... because all (target) addresses can be specified by the base address +
offset
6(b)(i) 0000 0100 1
6(b)(ii) 1101 1111 1
6(b)(iii) 0010 0111 1
6(c) 1 mark for a correct name: 1
• input and output of data
• arithmetic operations
• unconditional and conditional instructions
• compare instructions
(a) The diagram shows the hardware and software used to retrieve files stored on the cloud.
Internet
Laptop Firewall A Service X
Provider
B
Complete the following table by writing the answer for each row.
Answer
The name of device A that allows the laptop to connect to the internet
A type of cloud, X
An example of an application, B, that can run on the cloud
[3]
(b) Give one advantage and two disadvantages of transmitting data using satellites instead of copper cables.
Advantage 1 ……
Disadvantage 1 ……
Disadvantage 2 ……
[3]
(c) Local Area Networks (LANs) can be made up of several subnetworks.
(i) Give two benefits of dividing a network into subnetworks by subnetting the LAN.
1 ……
2 ……
[2]
(ii) A subnet mask is used when subnetting a LAN.
Two devices on the LAN are located in different subnetworks.
The IP addresses and corresponding subnet masks are shown:
Device IP address Subnet mask
10.10.12.1 255.0.0.0
192.168.12.4 255.255.255.0
Identify the following network ID and host ID.
The network ID for the device with the IP address 10.10.12.1
The host ID for the device with the IP address 192.168.12.4
[2]
Mark scheme
7(a) 1 mark for each correct answer: 3
Answer
The name of device A that allows Router
the laptop to connect to the internet
A type of cloud, X Public (cloud)
An example of an application, B, Email / Graphics / Word processor /
that can run on the cloud, Spreadsheet / Game / Database, etc.
7(b) 1 mark for a correct advantage: 3
• not fixed to a single location
• allows access in remote / rural areas
1 mark for each correct disadvantage (max 2):
• high latency / lag / slow to connect
• more expensive than wired methods, as need extra equipment
• signal is affected by bad weather
• the transmission speed is slower than fixed line broadband
• direct line of sight needed
7(c)(i) 1 mark for each bullet point (max 2) 2
Examples:
• improves security
• reduces congestion
• allows extension of the network / devices attached
• aids day-to-day management
• improves performance
7(c)(ii) 1 mark for each correct answer: 2
• network ID = 10
• host ID = 4
(a) (i) Explain why some programs are distributed under an open source licence.
…… [2]
(ii) Explain how a programmer benefits from distributing a program under a commercial licence.
…… [2]
(b) A commercial program for a vehicle repair garage includes an Artificial Intelligence (AI) module that can diagnose faults and suggest repairs.
Describe one economic impact the AI module may have on the garage.
…… [2]
Mark scheme
8(a)(i) 1 mark for each bullet point (max 2): 2
• to allow users to customise the code
• to allow errors to be reported / identified / fixed by users
• to allow additional features to be added to the code
• to allow for collaboration
8(a)(ii) 1 mark for each correct point (max 2) 2
Example:
• enables the program to be copyrighted
• prevents illegal changes to the program / protects the source code
• prevents illegal copies of the program being made
• a fee can be charged for the program
8(b) 1 mark for a correct economic impact and 1 mark for corresponding 2
description
Example:
• reduce costs to the garage
• ... because less time taken for diagnosis
• increase profits for the garage
• ... as technicians spend more time repairing, so completing more jobs in a
day
• decrease costs passed to customer
• ... so garage may gain customers
• profit margins can be reduced
• ... because program may be expensive to buy / maintain / update
(a) (i) Convert the unsigned binary value into hexadecimal.
10010011
Answer …… [1]
(ii) Convert the unsigned binary value into denary.
10010011
Answer …… [1]
(b) State two benefits of using Binary Coded Decimal (BCD) to represent values.
Benefit 1 ……
Benefit 2 ……
[2]
Mark scheme
9(a)(i) 93 1
9(a)(ii) 147 1
9(b) 1 mark for each correct benefit (max 2) 2
Examples:
• straightforward to convert to / from BCD and denary
• ... so it is less complex to encode and decode for programmers
• easier for digital equipment use BCD to display output information
• can represent monetary values exactly
(a) Explain the importance of feedback in a control system.
…… [3]
(b) (i) Identify one sensor that could be used in a car alarm system.
Justify your choice.
Sensor ……
Justification ……
[2]
(ii) The car alarm is an example of an embedded system.
Describe the characteristics of an embedded system.
…… [3]
Mark scheme
10(a) 1 mark for each bullet point: 3
• to ensure the system operates with the given criteria
• ... by enabling system output to affect subsequent system input
• ... thus allowing conditions to be automatically adjusted
10(b)(i) 1 mark for identification of a suitable sensor 2
1 mark for corresponding justification
Example:
• sound sensor
• if a sound occurs inside the car the alarm is activated
• infra-red sensor
• senses the heat of person in the car / infra-red beams are broken
• pressure sensor
• an intruder sits in the driver’s seat
10(b)(ii) 1 mark for each bullet point (max 3): 3
• the embedded system is built into / integrated (into the car alarm)
• combination of hardware and software designed for a specific function
• must have a processor, memory and input / output
• The system is not easily changed/updated by the car owner
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Where can I find the 9618/13 October/November 2022 mark scheme?+
On this page, free: the mark scheme for AS & A Level Computer Science 9618/13, October/November 2022 (9618_w22_ms_13), and the question paper (9618_w22_qp_13), to read or download, with each question's marking points written out underneath.
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Computer Science 9618/13 for October/November 2022 is out of 75 marks, with 1 hour 30 minutes to answer it.
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Yes. Upload your answers to 9618/13/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.