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A Level Computer Science 9618 Paper 11, Oct/Nov 2024

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9618/11 · Oct/Nov 2024

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1
a

State one difference between a tebibyte and a gigabyte.

[1]
b(i)

Convert the unsigned binary integer into hexadecimal. 110001100111 Answer ...............................................................................

[1]
b(ii)

Convert the two’s complement binary number into denary. 100110010111 Answer ...............................................................................

[1]
b(iii)

Convert the Binary Coded Decimal (BCD) into denary. 010101110011 Answer ...............................................................................

[1]
c

Subtract the denary number 23 from the two’s complement binary number 01001010 Perform this calculation using binary subtraction. Show your working. Working ..................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... Answer ...............................................................................

[2]
d

State one reason why binary addition and subtraction can result in overflow.

[1]
2

A shop repairs electronic devices, for example mobile phones and tablet computers. The shop owner stores the data about the repairs using a file-based approach.

a

Give one limitation of using a file-based approach to store the data and explain how a relational database addresses this limitation. Limitation .................................................................................................................................. ................................................................................................................................................... Explanation ............................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ...................................................................................................................................................

[3]
b(i)

The shop owner creates a relational database called FIXIT. The database stores data about the customers and the devices for repair. Some devices need new parts that are ordered from suppliers. The database FIXIT is designed to include the following tables: PART(PartID, Description, Price, SupplierID) CUSTOMER(CustomerID, FirstName, LastName, ContactNumber) REPAIR(RepairNumber, StartDate, EndDate, CustomerID, Device) REPAIR_PART(PartID, RepairNumber, Quantity) Complete the entity-relationship (E-R) diagram for the given tables.

[3]
b(ii)

The table shows sample data for the table REPAIR_PART. Write a Structured Query Language (SQL) script to define the table REPAIR_PART. Include constraints (restrictions) on the data that can be entered into each field where appropriate.

[5]
b(iii)

Suppliers send invoices to the company for the parts that are used. A new table, INVOICE, stores the data about each invoice and whether it has been paid or not. The design for the table INVOICE is shown: INVOICE(InvoiceID, SupplierID, AmountDue, Paid, DatePaid) The table shows sample data for the table INVOICE. Write an SQL script to return the total amount due to the supplier with the ID of JK675 for all the invoices that have not currently been paid.

[3]
c

Complete the table by writing a definition for each of the database terms.

[3]
3

A computer system has a dual-core Central Processing Unit (CPU).

a

State the purpose of the system clock and the Control Unit (CU) in a CPU. System clock ............................................................................................................................. ................................................................................................................................................... CU ............................................................................................................................................. ...................................................................................................................................................

[2]
b(i)

The number of cores in the processor affects the performance of the computer system. Identify one other feature of a processor that can affect the performance of a computer system and state why it affects the performance. Feature .............................................................................................................................. ........................................................................................................................................... Reason .............................................................................................................................. ...........................................................................................................................................

[2]
b(ii)

A solid state (flash) memory drive is automatically recognised by the computer when it is plugged into a port in the computer. Identify an appropriate type of port to connect the solid state memory drive to the computer. Explain how this port provides an automatic connection. Port .................................................................................................................................... Explanation ........................................................................................................................ ........................................................................................................................................... ........................................................................................................................................... ...........................................................................................................................................

[3]
c

Identify two disadvantages of using Dynamic RAM (DRAM) instead of Static RAM (SRAM) in a computer system. 1 ................................................................................................................................................ ................................................................................................................................................... 2 ................................................................................................................................................ ...................................................................................................................................................

[2]
d(i)

The computer system is used to store data received from a temperature sensor every five seconds. The data is stored on an optical disc using an optical disc reader/writer. Describe the principal operation of an optical disc reader/writer.

[4]
d(ii)

The computer uses a buffer when writing data to the optical disc. Explain the use of a buffer when writing data to the optical disc.

[3]
4

A student uses a laptop to write a program that is saved as a text file.

a(i)

The laptop has utility software and an Operating System (OS). Describe the file management tasks carried out by an OS.

[2]
a(ii)

Explain the need for back-up software.

[2]
b(i)

The student compresses the file before it is emailed to their teacher as an attachment. Explain the benefits to the teacher of the attachment being a compressed file.

[3]
b(ii)

Describe one lossless method of compressing a text file.

[3]
c

The student used a program library when writing their program. Explain the benefits to the student of using library files when writing a program.

[3]
d(i)

The program code is written using an Integrated Development Environment (IDE). One presentation feature found in a typical IDE is prettyprint. Identify and describe one other presentation feature found in a typical IDE. Feature .............................................................................................................................. Description ........................................................................................................................ ........................................................................................................................................... ...........................................................................................................................................

[2]
d(ii)

One debugging feature found in a typical IDE is single stepping. Identify and describe one other debugging feature found in a typical IDE. Feature .............................................................................................................................. Description ........................................................................................................................ ........................................................................................................................................... ...........................................................................................................................................

[2]
5

A security system has both a floodlight (very bright light) and an audio alarm. The data from multiple sensors is analysed and used to: • turn on the floodlight • sound the audio alarm. Sensors can be used to detect: • if doors are open • the external daylight level • if people are detected within a set distance.

a

Complete the table to identify the most appropriate type of sensor for each scenario.

[1]
b

The floodlight (X) and audio alarm (Y) operate according to the following criteria: The floodlight turns on (X = 1) if: • the security system is switched on and • the external daylight level is low and • a person is detected within 2m. The audio alarm turns on (Y = 1) if: • the security system is switched on and • one or more doors are open, or a person is detected within 2m. Write logic expressions for the security system. X = ............................................................................................................................................ ................................................................................................................................................... Y = ............................................................................................................................................ ...................................................................................................................................................

[2]
c

Explain whether the security system is an example of a monitoring system or a control system.

[3]
6

A car park system uses a camera to record the registration number of each car as it enters and leaves the car park. Explain how artificial intelligence is used in the car park system to identify the car’s registration number.

[4]
7

Software is distributed with a licence.

a

Give two benefits of distributing software using a shareware software licence. 1 ................................................................................................................................................ ................................................................................................................................................... 2 ................................................................................................................................................ ...................................................................................................................................................

[2]
b

Give two benefits of distributing software using a commercial software licence. 1 ................................................................................................................................................ ................................................................................................................................................... 2 ................................................................................................................................................ ...................................................................................................................................................

[2]
8

A computer designed using the Von Neumann model for a computer system contains general purpose registers and special purpose registers.

a

Describe the purpose of the Status Register (SR).

[2]
b

Identify two differences between general purpose registers and special purpose registers. 1 ................................................................................................................................................ ................................................................................................................................................... ................................................................................................................................................... 2 ................................................................................................................................................ ................................................................................................................................................... ...................................................................................................................................................

[2]

Mark scheme

9618/11 · Oct/Nov 2024

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1a · 1 mark

  • 1 mark

    A tebibyte = 1024 gibibytes / 1 048 576 kibibytes / 2^40 bytes whereas a gigabyte = 1000 megabytes / 1 000 000 kilobytes / 10^9 bytes // Tebi is binary prefix giga is denary prefix

1b(i) · 1 mark

  • 1 mark

    C67

1b(ii) · 1 mark

  • 1 mark

    −1641

1b(iii) · 1 mark

  • 1 mark

    573

1c · 2 marks

  • 1 mark

    Working: Using the two’s complement and adding (23 in binary = 00010111 so minus 23 is 11101001, 0100 1010 + 1110 1001 = (1)0011 0011) OR Direct subtraction (0100 1010 – 0001 0111 = 0011 0011)

  • 1 mark

    Answer: 0011 0011

1d · 1 mark

  • 1 mark

    The answer cannot be represented in the number of bits available // The answer is larger than the maximum positive number that can be stored in the register // The answer is smaller than the most negative number that can be stored in the register

2a · 3 marks

  • 1 mark

    Limitation: Data redundancy // data duplication OR Data inconsistency / Poor data integrity OR The data structure used depends on the application

  • 1 mark

    First explanation point corresponding to the chosen limitation

  • 1 mark

    Second explanation point corresponding to the chosen limitation

2b(i) · 3 marks

  • 1 mark

    Correct relation between REPAIR_PART and PART (many-to-one)

  • 1 mark

    Correct relation between REPAIR and CUSTOMER (many-to-one)

  • 1 mark

    Correct third relation entity connection

2b(ii) · 5 marks

  • 1 mark

    Create table REPAIR_PART with opening and closing brackets, all statements inside the brackets

  • 1 mark

    PartID and RepairNumber as varchar (or equivalent)

  • 1 mark

    Quantity as integer

  • 1 mark

    At least 1 appropriate constraint

  • 1 mark

    Dual primary key

2b(iii) · 3 marks

  • 1 mark

    Select SUM of AmountDue

  • 1 mark

    From the correct table and one correct condition

  • 1 mark

    Second correct condition

2c · 3 marks

  • 1 mark

    Referential Integrity: All duplicate entries of data between tables are consistent // all foreign keys are matched to an appropriate primary key

  • 1 mark

    Candidate Key: A field that could be a primary key but is not // an attribute or smallest set of attributes in a table where no tuple has the same value

  • 1 mark

    Tuple: A row / record in a table // one instance of an entity in a table

3a · 2 marks

  • 1 mark

    System clock: To synchronise operations / ... by creating and transmitting timing signals on the control bus

  • 1 mark

    Control Unit: Sends/receives control signals along control bus / Reads an instruction from the contents of the memory location whose address is stored in PC / Coordinates/synchronises the activity of other components in the CPU / Manages the execution of instructions / Controls communication between the components in the CPU

3b(i) · 2 marks

  • 1 mark

    Feature: clock speed OR bus width

  • 1 mark

    Matching reason: Higher clock speed means that more F-E cycles are executed per second // Higher clock speed results in more throughput OR Larger bus width means that more data transferred at the same time

3b(ii) · 3 marks

  • 1 mark

    Port: USB / Universal Serial Bus

  • 1 mark

    Explanation point 1: A voltage change occurs when the drive is plugged in / The computer detects this voltage change / The code of the device is transferred to computer

  • 1 mark

    Explanation point 2: … the OS finds the code of the device in the list of devices / … and loads the appropriate device driver

3c · 2 marks

  • 1 mark

    DRAM requires constant refresh cycles unlike SRAM

  • 1 mark

    DRAM has lower access speed than SRAM

3d(i) · 4 marks

  • 1 mark

    The disc is spun at high speed

  • 1 mark

    A laser is shone onto the disc to read / write / … using optical head to move it into position / … it follows the spiral track from the centre outwards

  • 1 mark

    When writing the laser burns pits to represent the data / When reading the laser reflects from pits and lands

  • 1 mark

    The reflection from a pit and a land is different / ... the differences are interpreted as 1 or 0

3d(ii) · 3 marks

  • 1 mark

    The computer and optical disc reader/writer send and receive at different speeds / A buffer allows temporary storage of the data

  • 1 mark

    … so that the computer can transfer data to the buffer at the higher speed / ... and is not held up waiting for data to transfer // so the computer can carry on with other tasks

  • 1 mark

    ... so the optical disc reader/writer is not overloaded / … and so that data is transferred to optical disc reader/writer from the buffer at the slower rate

4a(i) · 2 marks

  • 1 mark

    Secondary storage space is divided into file allocation units / Space on secondary storage is allocated to particular files / Maintains/creates directory structures / Specifies the logical method of file storage e.g. FAT or NTFS / Provides file naming conventions

  • 1 mark

    Controls user access // implements access rights //implements password protection // Makes file sharing possible / Controls access to the file by other software / Specifies tasks that can be performed on a file e.g. open, close, delete, copy, create, move, etc / Allows searching for a file

4a(ii) · 2 marks

  • 1 mark

    To allow data to be retrieved / restored when lost

  • 1 mark

    To automatically make a duplicate copy of data… / …so the user does not have to remember to backup data / To make regular duplicate copies of data

4b(i) · 3 marks

  • 1 mark

    Less of the teacher’s storage space is used / ... so more student work can be stored

  • 1 mark

    Transmission time is reduced / … so the teacher does not have to wait as long for it to arrive

  • 1 mark

    Bandwidth usage is reduced / … so other transmissions are not adversely affected / Less data allowance is used on the teacher’s email system

4b(ii) · 3 marks

  • 1 mark

    Run-Length Encoding // RLE

  • 1 mark

    Repeated sequences of the same characters are replaced by a single copy of the character

  • 1 mark

    ... and a count of the number of characters

4c · 3 marks

  • 1 mark

    It saves development time for the student / … by using pre-written code

  • 1 mark

    There is less testing to do // the routines are more likely to work correctly / … because they have already been tested and are error-free / It results in a more robust program

  • 1 mark

    Subroutines can be used that they do not have the skill to write / … which enables a more complex program to be written

4d(i) · 2 marks

  • 1 mark

    Correct name: Expand/collapse code blocks OR Auto-indentation // auto-formatting

  • 1 mark

    Matching description: … sections of source code that are part of the same block can be expanded to see the content or collapsed so that the overall code is seen OR ... automatically indents/formats code as the user types so that the structure is clear // aids readability

4d(ii) · 2 marks

  • 1 mark

    Correct name: Breakpoints OR Report window // variable watch window

  • 1 mark

    Matching description: … stops the code running on a set line to view the current status/variable contents/program flow OR … shows the values in variables/data structures and how they change when each line is run

5a · 1 mark

  • 1 mark

    All 3 appropriate sensors: Door open: Pressure sensor // Infra-red; Daylight-level: Light sensor; Person detected: Infra-red

5b · 2 marks

  • 1 mark

    X = E AND A AND C

  • 1 mark

    Y = E AND (B OR C OR D)

5c · 3 marks

  • 1 mark

    There is no use of feedback // The light and the alarm are just warnings

  • 1 mark

    The output of the floodlight or the audio alarm does not affect the input of data from the sensors

  • 1 mark

    The system does not have any actuators

6 · 4 marks

  • 1 mark

    It uses image recognition

  • 1 mark

    The pixels of each image from the camera are stored / … and matched to the expected shape/size/colour of registration number

  • 1 mark

    It uses optical character recognition

  • 1 mark

    The pixels within the registration number area identified are analysed / … and compared to expected characters/letters/numbers

7a · 2 marks

  • 1 mark

    The user can test/trial the program before purchasing to see whether it meets needs / There is no initial cost

  • 1 mark

    Users who try the software may spread the word so the developer gets more custom / The developer can get feedback to improve the program

7b · 2 marks

  • 1 mark

    The owner/developer can earn a fee

  • 1 mark

    Comprehensive support is usually offered so problems can be easily solved / The software is usually well tested so few bugs

8a · 2 marks

  • 1 mark

    To store the value of flags/bits / … that can be changed/set/cleared after arithmetic / logical operations

  • 1 mark

    To allow flags to be checked / … to change instruction sequence

8b · 2 marks

  • 1 mark

    Special purpose registers have a specified role in the machine whereas general purpose registers can be used for all purposes defined by the programmer

  • 1 mark

    Special purpose registers hold the state of the program’s execution while general purpose registers hold the program’s data during operations

Questions

  1. 1
    Question 17 marks
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  2. 2
    Question 217 marks
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  3. 3
    Question 316 marks
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  4. 4
    Question 417 marks
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  5. 5
    Question 56 marks
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  6. 6
    Question 64 marks
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  7. 7
    Question 74 marks
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  8. 8
    Question 84 marks
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