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A Level Computer Science 9618 Paper 12, Oct/Nov 2023

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9618/12 · Oct/Nov 2023

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1

A factory makes chocolate bars. The factory uses a conveyor belt that moves the products from one stage of production to the next stage.

a

An automated system counts the number of chocolate bars made at the end of production. The system includes a sensor positioned above the conveyor belt. Identify one appropriate type of sensor that can be used.

[1]
b

A second automated system removes chocolate bars with an incorrect weight from the production line. Describe the role of an actuator in this second system.

[2]
c(i)

The factory has many different machines with embedded systems. Identify two features of embedded systems. 1 ........................................................................................................................................ ........................................................................................................................................... 2 ........................................................................................................................................ ...........................................................................................................................................

[2]
c(ii)

Identify one drawback of embedded systems.

[1]
2
a

State what is meant by the following terms in a relational database model. Entity ......................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... Primary key ............................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... Referential integrity ................................................................................................................... ................................................................................................................................................... ...................................................................................................................................................

[3]
b

Authentication is one method a Database Management System (DBMS) can use to improve the security of a database. Describe other methods that a DBMS can use to improve the security of a database.

[4]
c

The following database table is not normalised.

StudentNameDateOfBirthTutorGroupSubjectSubjectCode
Yuwei Chen01/09/2004SMHEnglish, Maths, Computer ScienceEN, MA, CS
Claudia Raj23/02/2005JMBMaths, Physics, ArtMA, PY, AR
Aamil Akram24/01/2005KMBArt, Design, English languageAR, DE, EN
Areeba Faraz21/12/2004SMHEnglish language, Chemistry, DesignEN, CH, DE

Explain how to modify the table to put it into First Normal Form (1NF).

[4]
3
a

State one difference between a kibibyte and a megabyte.

[1]
b(i)

Convert the denary value into a 12-bit two’s complement binary integer. −196 Answer ........................................................................................................................

[1]
b(ii)

Convert the Binary Coded Decimal (BCD) into denary. 100001100101 Answer ........................................................................................................................

[1]
b(iii)

Convert the unsigned binary integer into denary. 000111010110 Answer ........................................................................................................................

[1]
c

Identify one practical application of BCD and justify why BCD is used in this application. Application ................................................................................................................................ ................................................................................................................................................... Justification ............................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ...................................................................................................................................................

[2]
4
Figure 1 of 1 for question 4
a

Write the Boolean expression that corresponds to the following logic circuit.

[3]
b

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

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

State the meaning of privacy of data.

[1]
b

State the meaning of integrity of data.

[1]
c

Describe the following threats to a computer system. Phishing email .......................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... Spyware .................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ...................................................................................................................................................

[4]
6
a

A real-time video of a music concert needs to be streamed to subscribers. Tick (✓) one box to identify the most appropriate type of compression and justify your answer.

LossyLossless

Justification ............................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ...................................................................................................................................................

[3]
b

Explain the impact of changing the sampling resolution on the accuracy of a sound recording.

[3]
c

A bitmap image has a resolution of 2048 pixels wide and 1024 pixels high. The image has a bit depth of 10 bits per pixel. Estimate the file size of the bitmap image in mebibytes. Show your working. Working ..................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... Estimated file size in mebibytes ...............................................................................................

[2]
7

A Local Area Network (LAN) contains four devices: • a router • two laptop computers • a server.

a

The server has the IP address 192.168.3.2 Explain why this is not an IPv6 address.

[2]
b(i)

The LAN is set up as a star topology. Draw a diagram of the topology of the LAN.

[2]
b(ii)

Explain how data is transmitted between the two laptops in the LAN.

[2]
b(iii)

Subnetting can be used to separate a network into logical segments. Describe two other reasons why subnetting is used in a network. 1 ........................................................................................................................................ ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... 2 ........................................................................................................................................ ........................................................................................................................................... ........................................................................................................................................... ...........................................................................................................................................

[4]
c

State three tasks performed by devices to deal with collisions when using the Carrier Sense Multiple Access /Collision Detection (CSMA/CD) protocol in a network. 1 ................................................................................................................................................ ................................................................................................................................................... 2 ................................................................................................................................................ ................................................................................................................................................... 3 ................................................................................................................................................ ...................................................................................................................................................

[3]
d

The following incomplete table contains types of IP addresses and their descriptions. Complete the table by writing the missing types of IP addresses and the missing descriptions.

Type of IP addressDescription
................................................................an IP address that is assigned to a device
................................................................to allow direct access on the internet
static IP address................................................................
................................................................
................................................................
................................................................
................................................................an IP address used for internal LAN
................................................................communication only
dynamic IP address................................................................
................................................................
................................................................
................................................................
[4]
8

A computer has an Operating System (OS).

a

State one purpose of the Operating System.

[1]
b

The Operating System has utility software. The purpose of some utility software is to improve security. Identify one example of utility software that is not intended to improve security. Explain why this software is needed. Utility software .......................................................................................................................... Explanation ............................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ...................................................................................................................................................

[3]
c(i)

An optical disc reader/writer is connected to the computer. Give the name of one port that can provide a connection for the optical disc reader/writer.

[1]
c(ii)

Describe the roles of the address bus, the data bus and buffers in the process of writing data to the optical disc reader/writer.

[3]
9

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

InstructionExplanation
OpcodeOperand
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#nImmediate addressing. Load the number n to IX
STO<address>Store the contents of ACC at the given address
ADD#nAdd the denary number n to the ACC
JMP<address>Jump to the given address
INC<register>Add 1 to the contents of the register (ACC or IX)
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
INKey in a character and store its ASCII value in ACC
OUTOutput to the screen the character whose ASCII value is stored in ACC
ENDReturn control to the operating system

<address> can be an absolute or a symbolic address # denotes a denary number, e.g. #123

a

The instructions in the processor’s instruction set can be grouped according to their function. Identify the instruction group for each of the following opcodes. IN .............................................................................................................................................. ADD ............................................................................................................................................ JPE ............................................................................................................................................ CMI ............................................................................................................................................

[4]
b

The current contents of main memory and selected values from the ASCII character set are given on page 15. Trace the program currently in memory using the trace table when the input is ‘1’.

[4]

Mark scheme

9618/12 · Oct/Nov 2023

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1a · 1 mark

  • 1 mark

    infra-red / proximity (sensor)

1b · 2 marks

  • 1 mark

    Actuator generates a signal / causes an action / converts electrical energy into a mechanical force

  • 1 mark

    ... to push an arm // to open a trap door // to pick up the chocolate bar with the incorrect weight

1c(i) · 2 marks

  • 1 mark

    Dedicated to a single task // limited number of functions

  • 1 mark

    Built into a larger system // integrated into a larger system

  • 1 mark

    An embedded system must contain a processor, memory and an I/O capability // Dedicated hardware

1c(ii) · 1 mark

  • 1 mark

    Difficult to change / update the firmware by the user // Difficult to upgrade devices to take advantage of new technology

  • 1 mark

    Cannot be easily adapted for another task

  • 1 mark

    Troubleshooting faults/upgrading is a specialist task

  • 1 mark

    Devices are often thrown away rather than repaired as difficult to upgrade or repair

2a · 3 marks

  • 1 mark

    Entity: An object about which data can be stored

  • 1 mark

    Primary key: The unique attribute / combination of attributes used to identify the record / tuple

  • 1 mark

    Referential integrity: Makes sure that if data is changed in one place the change is reflected in all related records - cascading update/delete // Makes sure that data that does not exist cannot be referenced // Ensures that every foreign key has a corresponding primary key // A logical dependency of a foreign key on a primary key // Ensures that the data in the database is consistent / up to date // Prevents records from being added/deleted/modified incorrectly // Makes sure any queries return accurate and complete results

2b · 4 marks

  • 1 mark

    Backup / recovery procedures / … automatically takes copies of the database and store off site on a regular basis / weekly, etc. / ... so that the data can be recovered if lost

  • 1 mark

    Use of access rights / … some users are given different access permissions to different tables / ... read/write, read only, full access, etc.

  • 1 mark

    Views / … different users are able to see different parts of the database / ... only see what users need to see // by example

  • 1 mark

    Record and table locking / … prevents simultaneous access to data / ... so updates are not lost // data is not overwritten

  • 1 mark

    Encryption / ... the data is turned into ciphertext / ... so it cannot be understood without a decryption key

2c · 4 marks

  • 1 mark

    Identify repeating groups of attributes ...

  • 1 mark

    ... Subject and SubjectCode

  • 1 mark

    Ensure each field is atomic

  • 1 mark

    ... StudentName should be split into e.g. FirstName and LastName

  • 1 mark

    Identify the primary key for the table

3a · 1 mark

  • 1 mark

    Either kibibyte = 1,024 bytes // 2^10 bytes and megabyte = 1000 kilobytes //1 000 000 bytes // 10^3 kilobytes // 10^6 bytes Or kibi is binary prefix and mega is denary prefix

3b(i) · 1 mark

  • 1 mark

    1111 0011 1100

3b(ii) · 1 mark

  • 1 mark

    865

3b(iii) · 1 mark

  • 1 mark

    470

3c · 2 marks

  • 1 mark

    1 mark for a correct application

  • 1 mark

    1 mark for a corresponding justification

4a · 3 marks

  • 1 mark

    A NAND B

  • 1 mark

    NOT(B XOR C)

  • 1 mark

    Final NAND

4b · 2 marks

  • 1 mark

    First set of rows (top 4 rows: 0, 0, 1, 0)

  • 1 mark

    Second set of rows (bottom 4 rows: 1, 1, 1, 1)

5a · 1 mark

  • 1 mark

    Ensuring data can only be accessed by / disclosed to authorised persons // Ensuring data cannot be accessed by / disclosed to unauthorised persons

5b · 1 mark

  • 1 mark

    Ensuring the accuracy / completeness / consistency of data (during / after processing) // Ensuring the data is up to date

5c · 4 marks

  • 1 mark

    Phishing email: The email pretends to be from an official body

  • 1 mark

    Phishing email: ... persuading individuals to disclose private information // by example such as bank details // or requesting authentication by redirecting to an unofficial/unauthorised website // inviting a user to click a link

  • 1 mark

    Spyware: Malware downloaded without the user’s knowledge

  • 1 mark

    Spyware: ... which secretly records the user’s actions / keystrokes on the computer // and sends logs of the actions to a third party

6a · 3 marks

  • 1 mark

    Lossy compression (ticked): Loss of quality will not be noticed // Needs to be viewed in real time so less bandwidth needed if file size smaller // Smaller file sizes will reduce buffering so the video will play more smoothly // Viewers may watch on different devices, so may not need high quality resolution

  • 1 mark

    Lossless compression (ticked): Original recording may not have been made in high resolution // Could be streaming to high bandwidth devices // The reduction in the file size is sufficient for the receiving device // Viewers do not want any loss of quality

  • 1 mark

    Any other valid point from either compression type

6b · 3 marks

  • 1 mark

    Increase/decrease: number of bits used for each sample is increased / decreased

  • 1 mark

    Increase/decrease: more / fewer values available to represent each sample // more / fewer amplitudes can be represented/stored // each binary amplitude/note in the digital recording is closer to / further from the analogue amplitude/note

  • 1 mark

    Increase/decrease: quantisation errors are reduced / increased // the digital soundwave is closer to / less like the original analogue soundwave

6c · 2 marks

  • 1 mark

    Working: (2048 ⨯ 1024 ⨯ 10) / (8 ⨯ 1024 ⨯ 1024)

  • 1 mark

    Answer: 2.5 mebibytes

7a · 2 marks

  • 1 mark

    Only has four groups of digits // IPv6 has eight groups

  • 1 mark

    Uses dotted notation instead of colons

  • 1 mark

    Because it is a 32 bit / 4 byte address // IPv6 is 128 bits / 16 bytes

7b(i) · 2 marks

  • 1 mark

    server only connected to router

  • 1 mark

    two laptop computers connected only to router

7b(ii) · 2 marks

  • 1 mark

    The data from the sending laptop is transmitted to the router

  • 1 mark

    The data has address of recipient

  • 1 mark

    The router determines recipient’s destination address / ... by using a routing table

  • 1 mark

    The router transmits data directly / only to recipient

7b(iii) · 4 marks

  • 1 mark

    Use 1: To improve the security of the LAN // To make the network management easier // To make the network easier to expand // For better control of network growth // To improve network performance / To reduce network congestion

  • 1 mark

    Corresponding expansion for Use 1

  • 1 mark

    Use 2: Second distinct use from the list

  • 1 mark

    Corresponding expansion for Use 2

7c · 3 marks

  • 1 mark

    To monitor the communications channel

  • 1 mark

    To send data only when there is no data being transmitted / the line is quiet / idle

  • 1 mark

    To detect a collision and then stop transmissions of further data // transmit a jamming signal

  • 1 mark

    To calculate a random wait time / back-off time / ... then retransmit the data after that random wait time

  • 1 mark

    Increase random time if multiple collisions

7d · 4 marks

  • 1 mark

    public IP address: an IP address that is assigned to a device to allow direct access on the internet

  • 1 mark

    static IP address: an IP address that is fixed / doesn’t change each time a device re-joins a LAN / network

  • 1 mark

    private IP address: an IP address used for internal LAN communication only

  • 1 mark

    dynamic IP address: an IP address that may be refreshed / changed each time a device re-joins a LAN / network

8a · 1 mark

  • 1 mark

    To hide the complexities of the hardware from the user // To provide a platform for software to run // To provide a user interface

8b · 3 marks

  • 1 mark

    1 mark for the name of the utility software

  • 2 marks

    2 marks for the explanation

8c(i) · 1 mark

  • 1 mark

    USB / Universal Serial Bus // HDMI

8c(ii) · 3 marks

  • 1 mark

    Buffers: A buffer temporarily holds data until it is ready to be transmitted to the device

  • 1 mark

    Address Bus: The address of the data to be written to the device (in RAM) is carried on the address bus

  • 1 mark

    Data Bus: All data to be written to the device / buffer is carried on the data bus

9a · 4 marks

  • 1 mark

    IN - Input and output of data

  • 1 mark

    ADD - Arithmetic operations

  • 1 mark

    JPE - Unconditional and conditional instructions

  • 1 mark

    CMI - Compare instructions

9b · 4 marks

  • 1 mark

    Rows 10 to 12 (IX=0, ACC=49, Mem[101]=49)

  • 1 mark

    Rows 13 to 16 (ACC=51, ACC=49)

  • 1 mark

    Rows 17 to 20 (ACC=65, IX=1, Mem[100]=65)

  • 1 mark

    Rows 13 to 22 (ACC=65, Output=A)

Questions

  1. 1
    Question 16 marks
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  2. 2
    Question 211 marks
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  3. 3
    Question 36 marks
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  4. 4
    Question 45 marks
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  5. 5
    Question 56 marks
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  6. 6
    Question 68 marks
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  7. 7
    Question 717 marks
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  8. 8
    Question 88 marks
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  9. 9
    Question 98 marks
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