IGCSE Computer Science 0478 Paper 11, Oct/Nov 2023

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0478/11 · Oct/Nov 2023

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1

A student uses a computer and several hardware devices to complete his schoolwork. The computer has a central processing unit (CPU).

a

The student uses a keyboard to complete his schoolwork. Tick (✓) one box to show which type of device the keyboard is. A input B memory C output D storage

[1]
b

The student uses a printer to print his schoolwork. Tick (✓) one box to show which type of device the printer is. A input B memory C output D storage

[1]
c

A component in the CPU sends signals to manage the fetch-decode-execute cycle. State the name of this component.

[1]
d

The CPU has a clock speed of 2.4Ghz. Describe what is meant by a 2.4Ghz clock speed.

[2]
e(i)

The CPU contains registers including the memory data register (MDR). Describe the role of the MDR in the fetch-decode-execute cycle.

[2]
e(ii)

Identify three other registers contained in the CPU. 1 ........................................................................................................................................ 2 ........................................................................................................................................ 3 ........................................................................................................................................

[3]
2

A car park has a payment machine that allows a customer to pay for their parking. The cost of parking is displayed as a denary number on a screen on the payment machine. The cost of parking is stored in two 8-bit binary registers. For the parking cost of $10.50: • register 1 stores the denary value 10 as binary • register 2 stores the denary value 50 as binary.

a

Give the parking cost that would be displayed on the payment machine when the registers store: • register 1: 00010001 • register 2: 01000110 Parking cost displayed $ ............................................................................... Working space

[2]
b

The parking cost of $14.98 is displayed on the payment machine. Give the 8-bit binary numbers that are stored in the registers to display the parking cost. Register 1 ................................................................................................................................. Register 2 ................................................................................................................................. Working space

[2]
c

The payment machine gives the customer a ticket when they have paid their parking cost. Each ticket has a 4-digit hexadecimal ticket number that is stored as binary. The binary number 1010000000111101 is stored for a customer’s ticket number. Give the hexadecimal ticket number that would be displayed on this customer’s ticket. Hexadecimal ticket number ................................................................................................ Working space

[4]
d

Explain why data input into the payment machine needs to be converted to binary.

[2]
e

When a customer is leaving the car park they arrive at a barrier. The customer needs to insert their ticket into a system at the barrier. This system reads the ticket number then checks whether the parking cost has been paid for the car. The barrier is raised if it has been paid. The system uses a microprocessor. Describe the role of the microprocessor in the system and how it checks whether the parking cost has been paid.

[4]
3

The table contains four descriptions about a computer system. Complete the table by writing the correct term for each description.

TermDescription
A collective term for the physical components of the computer system.
A type of software that provides services that the user requires and allows the user to perform tasks on the computer.
A type of software that manages the main functions of the computer, including managing files and managing memory.
A type of software that is stored in the read only memory (ROM). It includes the basic input output system (BIOS) and the bootloader.
[4]
4

Data is transmitted between a computer and a printer.

a

The data is transmitted one bit at a time down a single wire. The computer can transmit data to the printer and the printer can transmit data to the computer, using the same connection. Circle the two data transmission methods that will transmit data in this way. parallel full-duplex parallel half-duplex parallel simplex serial full-duplex serial half-duplex serial simplex

[2]
b

An odd parity check is used to detect errors in the data transmission. Explain how the odd parity check detects errors.

[4]
c

Another error detection method sends the data from the computer to the printer, then a copy of the data received is sent back from the printer to the computer. The two sets of data are compared to see if they match. State the name of this type of error detection method.

[1]
5

A musician is recording herself playing the music for a song on the piano.

a

Explain how the analogue sound is recorded and converted to digital.

[5]
b

State two ways that the accuracy of the recording could be increased. 1 ................................................................................................................................................ 2 ................................................................................................................................................

[2]
c

The musician compresses the sound file using lossless compression instead of lossy compression. Explain why the musician would choose to use lossless compression instead of lossy compression.

[3]
d

The musician types the words for the song into a document. Two character sets that can be used when converting text to digital are the American standard code for information interchange (ASCII) and Unicode. Explain the differences between the ASCII character set and the Unicode character set.

[4]
6

Draw and annotate a diagram to demonstrate how a firewall works.

[4]
7

Complete the statements about data packets and packet switching. Use the terms from the list. Some of the terms in the list will not be used. You should only use a term once. destination address first footer header last main data packets payload routers servers trailer Data is broken down into packets. A data packet has a packet ....................................................... that contains the packet number and the ....................................................... . Each packet could take a different path from the sender to the receiver; this is controlled by ...................................................... . Packets may arrive out of order. Once the ...................................................... packet has arrived, the packets are reordered.

[4]
8

Storage can be described as being magnetic, solid-state or optical.

a

Give two features of magnetic storage. 1 ................................................................................................................................................ ................................................................................................................................................... 2 ................................................................................................................................................ ...................................................................................................................................................

[2]
b

Give three features of solid-state storage. 1 ................................................................................................................................................ ................................................................................................................................................... 2 ................................................................................................................................................ ................................................................................................................................................... 3 ................................................................................................................................................ ...................................................................................................................................................

[3]
c

Give one example of each type of storage. Magnetic ................................................................................................................................... Solid-state ................................................................................................................................. Optical ......................................................................................................................................

[3]
9

An interrupt is a type of signal that is used in a computer.

a

State the name of the type of software that manages interrupts.

[1]
b

Describe how interrupts are used when a key is pressed on a keyboard.

[5]
c(i)

Interrupts can be hardware based or software based. A key press is one example of a hardware interrupt. Give two other examples of a hardware interrupt. 1 ........................................................................................................................................ ........................................................................................................................................... 2 ........................................................................................................................................ ...........................................................................................................................................

[2]
c(ii)

Give two examples of a software interrupt. 1 ........................................................................................................................................ ........................................................................................................................................... 2 ........................................................................................................................................ ...........................................................................................................................................

[2]

Mark scheme

0478/11 · Oct/Nov 2023

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1a · 1 mark

  • 1 mark

    A

1b · 1 mark

  • 1 mark

    C

1c · 1 mark

  • 1 mark

    Control unit

1d · 2 marks

  • 1 mark

    (The CPU completes) 2.4 billion

  • 1 mark

    … cycles/clock pulses per second

1e(i) · 2 marks

  • 1 mark

    Stores data …

  • 1 mark

    … that has been fetched/to be written to memory

1e(ii) · 3 marks

  • 1 mark

    Memory address register // MAR

  • 1 mark

    Program counter // PC

  • 1 mark

    Current instruction register // CIR

2a · 2 marks

  • 1 mark

    17

  • 1 mark

    70

2b · 2 marks

  • 1 mark

    Register 1: 00001110

  • 1 mark

    Register 2: 01100010

2c · 4 marks

  • 1 mark

    A

  • 1 mark

    0

  • 1 mark

    3

  • 1 mark

    D

2d · 2 marks

  • 1 mark

    It contains logic gates/switches …

  • 1 mark

    … that process the values 1 and 0 // have two states

2e · 4 marks

  • 1 mark

    Compares the ticket number received to stored data

  • 1 mark

    … that is a database/file of ticket numbers

  • 1 mark

    … checks the ticket number is listed as paid

  • 1 mark

    If the data matches/cost is paid it sends a signal to raise the barrier // If the data does not match/cost is not paid, the barrier remains down

3 · 4 marks

  • 1 mark

    hardware

  • 1 mark

    application software

  • 1 mark

    operating system

  • 1 mark

    firmware

4a · 2 marks

  • 1 mark

    Serial half-duplex

  • 1 mark

    Serial full-duplex

4b · 4 marks

  • 1 mark

    The number of 1 s/0 s are counted

  • 1 mark

    A parity bit is added to each byte/7 bits before transmission

  • 1 mark

    … to make the sum of the bits/1 or 0 s in each byte odd

  • 1 mark

    After transmission, if the number is odd no error is detected // After transmission, if the number is even an error is detected

4c · 1 mark

  • 1 mark

    Echo (check)

5a · 5 marks

  • 1 mark

    (The analogue sound is) recorded using a microphone

  • 1 mark

    The sound wave is sampled

  • 1 mark

    … measuring the height/amplitude

  • 1 mark

    Each amplitude has a unique binary value

  • 1 mark

    The sample rate is set / … that is the number of samples taken per second / The sample resolution is set / … that is the number of bits used for each sample / Each sample taken is converted to binary

5b · 2 marks

  • 1 mark

    Increase the sample rate

  • 1 mark

    Increase the sample resolution

5c · 3 marks

  • 1 mark

    They want to be able to edit the original sound file

  • 1 mark

    They want the highest sound quality for the file // They want the sound to be closest to the original recording

  • 1 mark

    … using lossy would reduce the sound quality // … using lossy will permanently remove some of the data // no data will be permanently removed with lossless

5d · 4 marks

  • 1 mark

    ASCII has limited/fewer characters // Unicode has a more characters

  • 1 mark

    ASCII covers a limited set of languages/fewer languages // Unicode includes many/more languages/emojis

  • 1 mark

    ASCII requires 7/8 bits per character // Unicode requires up to 16/32 bits per character

  • 1 mark

    ASCII has 128/256 characters // Unicode has 65 536/4 294 967 296 characters // approx. 60/70 thousand/4 billion characters

6 · 4 marks

  • 1 mark

    Traffic passing both ways through the firewall

  • 1 mark

    An indication that criteria is set for the firewall

  • 1 mark

    Traffic is compared to criteria

  • 1 mark

    Traffic being rejected if it does/does not meet criteria // Traffic being accepted if it does/does not meet criteria

7 · 4 marks

  • 1 mark

    header

  • 1 mark

    destination address

  • 1 mark

    routers

  • 1 mark

    last

8a · 2 marks

  • 1 mark

    Data is stored on platters / (Platters) are divided into tracks and sectors / Has components that are spun

  • 1 mark

    Data is read/written using a read/write arm / Data is read/written using electromagnets / Magnetic field determines the binary value / It is non-volatile

8b · 3 marks

  • 1 mark

    Flashes data onto chips / Uses transistors

  • 1 mark

    Uses NAND/NOR technology / Uses control gates / Uses flow gates

  • 1 mark

    Controls the flow of electrons / It can be volatile or non-volatile

8c · 3 marks

  • 1 mark

    Magnetic: HDD / Magnetic tape / Floppy disk / Magnetic strip

  • 1 mark

    Solid state: SSD / USB drive / SD card / RAM

  • 1 mark

    Optical: CD / DVD / Blu-ray

9a · 1 mark

  • 1 mark

    Operating system // Interrupt handler

9b · 5 marks

  • 1 mark

    Key press generates the interrupt

  • 1 mark

    Interrupt given a priority

  • 1 mark

    Interrupt is sent to CPU

  • 1 mark

    Interrupt is placed in a queue

  • 1 mark

    CPU stops current task to check the queue/service the interrupt … / … using an interrupt service routine / If key press is highest priority the interrupt is processed

9c(i) · 2 marks

  • 1 mark

    Moving the mouse / Clicking a mouse button / Plugging in a device

  • 1 mark

    Paper jam in printer / Printer out of paper

9c(ii) · 2 marks

  • 1 mark

    Division by zero

  • 1 mark

    Two processes accessing the same memory location // Null value

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