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A Level Computer Science 9618 Paper 12, May/June 2024

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9618/12 · May/June 2024

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1
a

Describe the operation of each of the following logic gates: NAND ....................................................................................................................................... ................................................................................................................................................... NOR .......................................................................................................................................... ................................................................................................................................................... XOR .......................................................................................................................................... ................................................................................................................................................... OR ............................................................................................................................................ ...................................................................................................................................................

[4]
b

Draw a logic circuit for this logic expression: X=NOT ((A AND B) OR (C AND D))

[2]
2

A computer game is being designed that users will be able to play using a virtual reality (VR) headset.

a

Complete the description of the principal operation of a VR headset. A headset can have one or two .......................................................... that output the image to the user. The headset has speakers that output surround sound to give a realistic experience. The user’s head movements are detected using a sensor. This sensor is a .......................................................... . The data is transmitted to a microprocessor that analyses the data to identify the .......................................................... of movement. Some headsets use .......................................................... that record the user’s eye movements for analysis.

[4]
b

The computer uses a buffer when transmitting data to the VR headset. Explain how a buffer is used when data is transmitted between the computer and the VR headset.

[3]
c

The VR headset has Electrically Erasable Programmable Read Only Memory (EEPROM). Explain the benefits of using EEPROM instead of other types of Read Only Memory (ROM) in the VR headset.

[3]
d(i)

The computer can transmit a video made from bitmap images and vector graphic animations to the VR headset. Describe how the data for a bitmapped image is encoded.

[3]
d(ii)

Describe the contents of a vector graphic drawing list.

[2]
d(iii)

The bitmap video is not compressed before transmission to the VR headset. Give two reasons why the video does not need to be compressed. 1 ........................................................................................................................................ ........................................................................................................................................... 2 ........................................................................................................................................ ...........................................................................................................................................

[2]
3

An assessment board scans exam papers and stores the digitised papers on a server. Exam markers download the digitised papers to mark. The exam markers then upload the mark for each paper.

a(i)

The assessment board needs to make sure the data stored on the server is secure. Authentication methods can help to protect the server against hackers. Identify one other security measure that helps to protect the server from hackers. Describe how the security measure works. Security measure .............................................................................................................. Description ........................................................................................................................ ........................................................................................................................................... ........................................................................................................................................... ...........................................................................................................................................

[3]
a(ii)

Identify one security measure that helps to protect the data when it is being transmitted to its destination. Describe how the security measure works. Security measure .............................................................................................................. Description ........................................................................................................................ ........................................................................................................................................... ........................................................................................................................................... ...........................................................................................................................................

[3]
b

The exam markers use software that operates as a thin-client to mark the exam papers. Complete the table by identifying two characteristics of a thin-client. Describe how each characteristic will be used in this software.

[4]
c(i)

Data transmitted on the internet passes through multiple different systems. Describe the role of routers in the transmission of data through the internet.

[2]
c(ii)

Describe the role of the PSTN (Public Switched Telephone Network) in the transmission of data through the internet.

[2]
4

An assessment board wants to store the marks students achieved in exams in a database named RECORDS. Part of the database design includes these two tables: EXAM(ExamID, Subject, Level, TotalMarks) EXAM_QUESTION(ExamQuestionID, ExamID, QuestionNumber, Question, MaxMark)

a

Identify the relationship between EXAM and EXAM_QUESTION.

[1]
b

Sample data for the table EXAM is shown:

ExamIDSubjectLevelTotalMarks
00956124Computer Science275
00956125Computer Science3120
00956126Mathematics2100
00956127Mathematics3150
00956128Physics270
00956129Physics380

Write a Structured Query Language (SQL) script to define the table EXAM.

[3]
c

The table EXAM_QUESTION has been created but the foreign key has not been linked. Write an SQL script to update EXAM_QUESTION and link the foreign key to EXAM.

[2]
d

The database also needs to store data about the students, the exams the students have taken and the marks the students achieved in each question of each exam. Describe the additional tables that will need to be included in the database and explain how all the tables in the database will be linked.

[5]
5

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).

InstructionExplanation
OpcodeOperand
LDM#nImmediate addressing. Load the number n to ACC
LDD<address>Direct addressing. Load the contents of the location at the given address to ACC
LDI<address>Indirect addressing. The address to be used is at the given address. Load the contents of this second 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
ADD#n/Bn/&nAdd the number n to the ACC
ADD<address>Add the contents of the given address to the ACC
SUB#n/Bn/&nSubtract 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:

AddressData
101
113
125
1311
1410
1516
1612

The current contents of the ACC and IX are shown: ACC: 10 IX: 0 Complete the table by writing the content of the ACC after each program has run.

Program numberCodeACC content
1LDI 15<br>SUB #1
2LDD 14<br>ADD 11
3LDM #11<br>ADD #3<br>SUB 16
4LDR #2<br>LDX 14<br>ADD #2
[4]
b

The processor includes these bit manipulation instructions:

InstructionExplanation
OpcodeOperand
AND#n/Bn/&nBitwise 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/Bn/&nBitwise 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/Bn/&nBitwise 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>

<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:

AddressData
2511000110
2611100001
2710000001
2811001101
2900001111

The current content of the ACC is shown: | 0 | 1 | 0 | 0 | 0 | 1 | 1 | 0 | Complete the table by writing the content of the ACC after each program has run. The binary number 01000110 is reloaded into the ACC before each program is run.

Program numberCodeACC content
1XOR 29
2AND #29
3OR B11111111
[3]
6

A computer has an Operating System (OS). Memory management and process management are two OS tasks. Explain how memory management and process management support multi-tasking.

[4]
7

A computer stores binary data.

a

Tick (✓) one box only to identify the largest file size. [ ] 3300 kibibytes [ ] 0.3 megabytes [ ] 3 mebibytes [ ] 3300 kilobytes

[1]
b

Subtract the denary number 10 from the denary number 100 using binary subtraction. Show your working. Working ..................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... Answer ....................................

[3]
c

Convert the hexadecimal number C0F into denary. Show your working. Working ..................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... Answer ....................................

[2]
8

A programmer uses an Integrated Development Environment (IDE) to write a computer program. The IDE has both a compiler and an interpreter as built-in translators.

a

The programmer decides to use the compiler when testing the final program. Describe the benefits of using the compiler during testing.

[2]
b

IDEs have many features other than built-in translators. Complete the table by identifying one other common IDE feature that can be used for each purpose. Describe how each feature helps the user during program development. Each feature must be different. Do not give translator as one of your features.

PurposeIDE featureDescription
for coding
for presentation
for debugging
[6]
c

The programmer uses program libraries when developing the program. Describe two benefits to the programmer of using program libraries. 1 ................................................................................................................................................ ................................................................................................................................................... 2 ................................................................................................................................................ ...................................................................................................................................................

[2]

Mark scheme

9618/12 · May/June 2024

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1a · 4 marks

  • 1 mark

    NAND: The output is 0 when both inputs are 1, otherwise the output is 1

  • 1 mark

    NOR: The output is 1 when both inputs are 0, otherwise the output is 0

  • 1 mark

    XOR: The output is 1 when one of the inputs is 1 and the other input is 0, otherwise the output is 0

  • 1 mark

    OR: The output is 0 when both inputs are 0, otherwise the output is 1

1b · 2 marks

  • 1 mark

    1 mark for both AND gates with correct inputs

  • 1 mark

    1 mark for correct OR and NOT gates with correct inputs and no superfluous gates

2a · 4 marks

  • 1 mark

    (LCD) displays/screens/lenses

  • 1 mark

    gyroscope/accelerometer

  • 1 mark

    direction/speed

  • 1 mark

    digital cameras

2b · 3 marks

  • 1 mark

    The buffer is used as a temporary store for data going to the headset

  • 1 mark

    Data is transferred into the buffer by the computer

  • 1 mark

    Data is retrieved from the buffer by the headset

2c · 3 marks

  • 1 mark

    EEPROM allows frequent/multiple read/write/erase operations

  • 1 mark

    ... so the headset can take advantage of new features

  • 1 mark

    ... without fully erasing the contents of the firmware in the headset first // can erase a particular byte or the whole EEPROM

2d(i) · 3 marks

  • 1 mark

    Image is made of pixels and each pixel has one colour

  • 1 mark

    Each colour has a unique binary code

  • 1 mark

    Code for the colour of each pixel is stored in sequence

2d(ii) · 2 marks

  • 1 mark

    List of objects in the drawing

  • 1 mark

    A list that stores the command/description/equation required to draw each object

2d(iii) · 2 marks

  • 1 mark

    Dedicated connection to the headset // not sharing bandwidth

  • 1 mark

    Already fast connection that can transmit the data without slowing

3a(i) · 3 marks

  • 1 mark

    1 mark for security measure (Firewall / Proxy server)

  • 1 mark

    First description point for how the chosen measure works

  • 1 mark

    Second description point for how the chosen measure works

3a(ii) · 3 marks

  • 1 mark

    1 mark for security measure (Encryption)

  • 1 mark

    Encodes/scrambles data

  • 1 mark

    ... so if it is intercepted it cannot be understood // Algorithm/key is required to decode the data

3b · 4 marks

  • 1 mark

    First characteristic

  • 1 mark

    First description of application to examination software

  • 1 mark

    Second characteristic

  • 1 mark

    Second description of application to examination software

3c(i) · 2 marks

  • 1 mark

    Receives packets from internet

  • 1 mark

    Analyses the destination IP address of each packet // Forwards the packet towards its destination ... using the routing table // Maintains/updates the routing table // Finds the most efficient route to the destination

3c(ii) · 2 marks

  • 1 mark

    The PSTN consists of many different types of communication lines (... therefore the digital data may need to be converted into a different form/analogue signal)

  • 1 mark

    Data is transmitted in both directions at the same time // duplex data transmission // Using a PSTN the communication passes through different switching centres/ISPs

4a · 1 mark

  • 1 mark

    1-to-many

4b · 3 marks

  • 1 mark

    Creating table EXAM with opening and closing brackets

  • 1 mark

    All fields with appropriate data types and commas at end of lines

  • 1 mark

    ExamID as primary key

4c · 2 marks

  • 1 mark

    Altering table EXAM_QUESTION

  • 1 mark

    Linking ExamID to ExamID in EXAM

4d · 5 marks

  • 1 mark

    STUDENT table identified with suitable Primary Key

  • 1 mark

    A linking table between STUDENT and EXAM with suitable Primary Key and appropriate name

  • 1 mark

    ... that includes the Primary Key of the STUDENT table as a Foreign Key to join with STUDENT

  • 1 mark

    ... and includes the Primary Key of the EXAM table as a Foreign Key to join with EXAM

  • 1 mark

    A linking table between STUDENT and EXAM_QUESTION 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 ExamQuestionID and the mark for that question)

5a · 4 marks

  • 1 mark

    Program 1: 11

  • 1 mark

    Program 2: 13

  • 1 mark

    Program 3: 2

  • 1 mark

    Program 4: 14

5b · 3 marks

  • 1 mark

    Program 1: 0100 1001

  • 1 mark

    Program 2: 0000 0100

  • 1 mark

    Program 3: 1111 1111

6 · 4 marks

  • 1 mark

    Point 1 from Memory management or Process management

  • 1 mark

    Point 2 from Memory management or Process management

  • 1 mark

    Point 3 from Memory management or Process management

  • 1 mark

    Point 4 from Memory management or Process management

7a · 1 mark

  • 1 mark

    3300 kibibytes

7b · 3 marks

  • 1 mark

    Converting 100 to binary 0110 0100 and 10 to binary 0000 1010

  • 1 mark

    Subtraction method - converting 10 to – 10 and adding // direct subtraction ...

  • 1 mark

    ... correct answer 0101 1010

7c · 2 marks

  • 1 mark

    1100 0000 1111 // 2048 + 1024 + 8 + 4 + 2 + 1 // (12 * 16²) + 15 // (12 * 16 * 16) + 15 // 3072 + 15

  • 1 mark

    3087

8a · 2 marks

  • 1 mark

    Creates an executable file

  • 1 mark

    ... so the code can be tested multiple times without having to recompile // ... so repeated testing takes less time

8b · 6 marks

  • 1 mark

    Identification of feature for coding

  • 1 mark

    Matching description of feature for coding

  • 1 mark

    Identification of feature for presentation

  • 1 mark

    Matching description of feature for presentation

  • 1 mark

    Identification of feature for debugging

  • 1 mark

    Matching description of feature for debugging

8c · 2 marks

  • 1 mark

    Saves programming/testing time as code does not have to be written/re-written from scratch // code does not have to be tested

  • 1 mark

    Code is already tested so it is more robust/likely to work // The programmer does not need to maintain the library // library routines are updated automatically // Can perform complex calculations that the programmer may be unable to do // Makes code more easily readable

Questions

  1. 1
    Question 16 marks
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  2. 2
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  3. 3
    Question 314 marks
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  4. 4
    Question 411 marks
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  5. 5
    Question 57 marks
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  6. 6
    Question 64 marks
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  7. 7
    Question 76 marks
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  8. 8
    Question 810 marks
    Mark scheme ›

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