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IGCSE Computer Science 0478 Paper 12, May/June 2025

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0478/12 · May/June 2025

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1

A computer stores data temporarily in random access memory (RAM).

a

RAM is one example of primary storage. Give one other example of primary storage.

[1]
b

Give one reason why data is only stored temporarily in the RAM.

[1]
c

The denary numbers 19 and 230 are converted to binary numbers to be stored in the RAM. Convert the two denary numbers to binary numbers. 19 .............................................................................................................................................. 230 ............................................................................................................................................ Working space

[2]
d

The hexadecimal numbers 35 and 8AD are converted to binary numbers to be stored in the RAM. Convert the two hexadecimal numbers to binary numbers. 35 .............................................................................................................................................. 8AD ........................................................................................................................................... Working space

[2]
e

The 8-bit binary numbers 01100101 and 01110000 are stored in RAM. The binary numbers are added together. Add the two binary numbers using binary addition. Give your answer in binary. You must show all your working. 0 1 1 0 0 1 0 1 + 0 1 1 1 0 0 0 0

[3]
f

An overflow occurs when two other 8-bit binary numbers are added together. Explain why the overflow error occurs.

[2]
g

The negative denary number –22 is stored in RAM. Negative denary numbers can be represented as binary using two’s complement. Give the two’s complement 8-bit binary integer that would be stored for the denary number –22. You must show all your working. Working space .......................................................................................................................... Two’s complement 8-bit binary integer .....................................................................................

[2]
2

A student has an image file stored on their computer.

a

The image file was taken by a digital camera. Tick (✓) one box to show whether a digital camera is an example of an input, output, process or storage device. A input B output C process D storage

[1]
b(i)

The size of the image file is 3072 bytes. Give the size of the image file in kibibytes (KiB).

[1]
b(ii)

State the number of nibbles in 1 byte. Working space

[1]
c(i)

The image file has a colour depth of 32 bits. State what is meant by a colour depth of 32 bits.

[1]
c(ii)

The colour depth of the image file is changed to 64 bits. Explain what effect this change has on the image file.

[2]
d

The student uses lossless compression to compress the image file. Explain how the image file is compressed using lossless compression.

[3]
3

A programmer writes a program to store and sort all the data for the books in her home library.

a

The programmer uses a high-level language to write the program. One reason for writing the program using a high-level language is that it is easier to read and write. Give two other reasons why the programmer chose to use a high-level language. 1 ................................................................................................................................................ 2 ................................................................................................................................................

[2]
b(i)

The programmer uses an integrated development environment (IDE) to write the program. One function of the IDE is to provide a translator. Complete the statements about translators. Use the terms from the list. Some of the terms will not be used. You should only use a term once. all together all assembler binary error executable file executing interrupt line by line partial code some translating whole code A compiler translates the ......................................................... at once before ......................................................... it. A compiler produces an error report that displays ......................................................... errors. An interpreter translates and executes the code ......................................................... . An interpreter stops execution when an ......................................................... is found and continues once it is corrected.

[5]
b(ii)

Give two other functions commonly found in an IDE. State the role of each function. Function 1 ......................................................................................................................... Role ................................................................................................................................... Function 2 ......................................................................................................................... Role ...................................................................................................................................

[4]
c(i)

The programmer wants to print a list of all her books on paper. Identify a suitable type of printer that she could use to print this list.

[1]
c(ii)

The programmer needs to connect the printer to her computer. The printer is on the same desk as her computer. Give a suitable method of data transmission that could be used to connect the computer to the printer. Explain your choice. Data transmission method ................................................................................................ Explanation .......................................................................................................................

[6]
c(iii)

An even parity check is used to detect errors in the data after it has been transmitted to the printer. Describe how an even parity check detects an error.

[4]
4

An employee uses a computer that has a Von Neumann architecture to complete many different tasks in their working day.

a

The computer has a central processing unit (CPU). Complete the table of components in the CPU and their descriptions.

[6]
b

The computer is an example of a general purpose computer and not an embedded system. Explain why the computer is not an embedded system.

[2]
5

A hospital has computers and technology that it uses when caring for its patients.

a

One computer is an expert system that is used to help diagnose a patient’s illness. The doctor inputs the patient’s symptoms into an interface and a diagnosis is output. Describe how the expert system decides the diagnosis.

[3]
b(i)

The hospital has a robot that is used to perform surgery. A doctor controls the robot from a different location to perform surgery on a patient. One feature of the robot is that it has electrical components. Give two examples of the electrical components of a robot. 1 ........................................................................................................................................ 2 ........................................................................................................................................

[2]
b(ii)

Explain the advantages of using the robot to perform surgery.

[4]
b(iii)

Explain one disadvantage of using the robot to perform surgery.

[2]
c(i)

Patients use a web page to log into their account to pay for the treatment they have received in the hospital. The patient enters the uniform resource locator (URL) for the web page into their browser and the web page is requested and displayed. Complete and annotate the diagram to show how the web page is requested for the patient.

[6]
c(ii)

A patient is making a payment through a secure connection. The secure connection is created using the secure socket layer (SSL) protocol. Explain how a secure connection is created using the SSL protocol.

[6]

Mark scheme

0478/12 · May/June 2025

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1a · 1 mark

  • 1 mark

    ROM

  • 1 mark

    Cache

1b · 1 mark

  • 1 mark

    It is volatile storage // Data is lost when the power is turned off.

  • 1 mark

    It needs to be regularly replaced by other data // The data regularly changes // Data needs to be constantly updated

1c · 2 marks

  • 1 mark

    10011

  • 1 mark

    11100110

1d · 2 marks

  • 1 mark

    0011 0101

  • 1 mark

    1000 1010 1101

1e · 3 marks

  • 1 mark

    One mark for each correct nibble (MAX 2)

  • 1 mark

    One mark for each correct nibble (MAX 2)

  • 1 mark

    One mark for a correct method of working e.g. showing carries.

1f · 2 marks

  • 1 mark

    The result is greater than 255 // The result is too large.

  • 1 mark

    Cannot be stored in 8 bits // Cannot be stored in the number of bits available for the register

1g · 2 marks

  • 1 mark

    One mark for a correct working method e.g. flip and add

  • 1 mark

    11101010

2a · 1 mark

  • 1 mark

    A

2b(i) · 1 mark

  • 1 mark

    3

2b(ii) · 1 mark

  • 1 mark

    2

2c(i) · 1 mark

  • 1 mark

    32 bits are used to represent each/a/one colour in the image // 2^(32) (approx. 4.3 billion) different colours can be used/are available for the image

2c(ii) · 2 marks

  • 1 mark

    The size of the image file increases.

  • 1 mark

    … as the number of bits used to represent/store a colour has increased

2d · 3 marks

  • 1 mark

    The size of the file is reduced without permanently removing any data.

  • 1 mark

    A compression algorithm is used.

  • 1 mark

    … such as Run length encoding/RLE.

  • 1 mark

    Repeating pixels are grouped/identified … // Patterns are identified …

  • 1 mark

    … and stored with the number of times they are repeated.

  • 1 mark

    … and indexed

3a · 2 marks

  • 1 mark

    It is easier to debug.

  • 1 mark

    Less likely to make errors.

  • 1 mark

    The program is machine independent/portable

3b(i) · 5 marks

  • 1 mark

    whole code

  • 1 mark

    executing

  • 1 mark

    all

  • 1 mark

    line by line

  • 1 mark

    error

3b(ii) · 4 marks

  • 1 mark

    Code editor: Allows the programmer to write/change the program.

  • 1 mark

    Run-time environment: Allows the user to run the code and see the output.

  • 1 mark

    Error diagnostics: Features that can be used to find errors in the code

  • 1 mark

    Auto-completion: A programmer starts to type a command word, and the IDE suggests option for completing it.

  • 1 mark

    Auto-correction: If a programmer misspells a command word it is changed to the correct spelling

  • 1 mark

    Prettyprint: The command words/identifiers are given different colours

3c(i) · 1 mark

  • 1 mark

    Inkjet

  • 1 mark

    Laser

3c(ii) · 6 marks

  • 1 mark

    Serial // Parallel

  • 1 mark

    Half-duplex // Full-duplex // Simplex

  • 1 mark

    serial: Serial would send bits in order // serial uses only one wire.

  • 1 mark

    serial: … so won’t be skewed // less likely to have errors

  • 1 mark

    serial: Serial transmission speed would be adequate.

  • 1 mark

    parallel: Parallel would transmit data faster.

  • 1 mark

    parallel: … as multiple bits are sent at the same time // … as multiple wires are used.

  • 1 mark

    parallel: For parallel, chance of skewing/errors would be low as short distance transmission only required.

  • 1 mark

    half/full duplex: To allow data to be sent in both directions

  • 1 mark

    half/full duplex: … so any interrupts/notifications for errors can be sent back to the computer.

  • 1 mark

    simplex: Data only needs to be sent one direction // Data transmission doesn’t need to be two-way.

  • 1 mark

    simplex: … as the printer may not need to send errors back to the computer

3c(iii) · 4 marks

  • 1 mark

    A parity bit is added to each byte.

  • 1 mark

    … to make the number of 1s/0s even // that will be 1 if the number of 1s/0s is odd // that will be 0 if the number of 1s/0s is even.

  • 1 mark

    The number of 1s/0s in each byte is counted after transmission.

  • 1 mark

    If any bytes have an odd number of 1s/0s an error is detected

4a · 6 marks

  • 1 mark

    Control unit // CU

  • 1 mark

    Arithmetic and logic unit // ALU

  • 1 mark

    It stores frequently used data/instructions

  • 1 mark

    It stores the address of the next instruction to be fetched

  • 1 mark

    It controls the number of fetch-decode-execute (FDE) cycles that are performed per second.

  • 1 mark

    Memory data register // MDR

4b · 2 marks

  • 1 mark

    An embedded system is designed to perform a dedicated/limited/single function // computer can be used to perform many different functions.

  • 1 mark

    An embedded system has dedicated hardware // computer has hardware that can be used by other devices.

  • 1 mark

    An embedded system has software that is not easily updated/reprogrammed // software can easily be updated/reprogrammed on the computer.

  • 1 mark

    An embedded system has a microprocessor // A computer has a CPU.

  • 1 mark

    An embedded system can be part of/built into a larger device // A computer is normally standalone

5a · 3 marks

  • 1 mark

    The inference engine is used …

  • 1 mark

    … to decide which questions to ask the user …

  • 1 mark

    … based on the previous data input.

  • 1 mark

    Symptoms input are located in/compared to knowledge base.

  • 1 mark

    … then applies the rule base to the knowledge base (to decide the diagnosis)

5b(i) · 2 marks

  • 1 mark

    Sensors

  • 1 mark

    Microprocessors

  • 1 mark

    Actuators

5b(ii) · 4 marks

  • 1 mark

    a doctor doesn’t need to travel to the hospital to do the surgery.

  • 1 mark

    … so it can be done by any specialist/doctor in the world.

  • 1 mark

    … so it can be done immediately without needing to wait for travel time // reduces the waiting time for the patient.

  • 1 mark

    … so the doctor may be better at the surgery as they won’t be tired from travel.

  • 1 mark

    … so travel costs are saved.

  • 1 mark

    Surgery with robots enhances precision/accuracy.

  • 1 mark

    … so a smaller incision can be made.

  • 1 mark

    … so the recovery time may be shorter.

  • 1 mark

    … as the components used to enter the body can be much smaller than a human hand.

  • 1 mark

    … so the surgery is safer/ more hygienic // by example e.g. can stop the doctor needing to be near an infectious patient.

  • 1 mark

    The surgery may have a higher rate of success

5b(iii) · 2 marks

  • 1 mark

    The internet connection could be lost/delayed … … so the surgery may not be able to continue.

  • 1 mark

    The robot will be expensive to buy/maintain … … this money could have been spent on other causes.

  • 1 mark

    The robot could be hacked …. … and endanger the patient’s life.

  • 1 mark

    Data could be corrupted in transmission … … changing the nature of the instruction for the robot.

  • 1 mark

    The robot’s hardware could malfunction … … so the surgery cannot continue

5c(i) · 6 marks

  • 1 mark

    Web browser identified as software used to send URL/requests or receives IP address/web page data

  • 1 mark

    URL/domain sent to DNS

  • 1 mark

    DNS searches for matching IP address

  • 1 mark

    If not found sent to another DNS

  • 1 mark

    IP address sent from DNS to patient’s computer

  • 1 mark

    Request sent from patient’s computer to web server (for web page)

  • 1 mark

    Web page/HTML data sent from web server to patient’s computer

5c(ii) · 6 marks

  • 1 mark

    Encrypted connection established …

  • 1 mark

    … using asymmetric encryption

  • 1 mark

    … to make any data sent meaningless

  • 1 mark

    The web browser asks the web server to identify itself.

  • 1 mark

    … by sending its digital certificate.

  • 1 mark

    The digital certificate is authenticated/validated by the web browser.

  • 1 mark

    If the certificate is authenticated/valid, the connection is secure/the transaction can begin.

  • 1 mark

    If the certificate is not authenticated/invalid, the connection is not secure/the transaction is cancelled/rejected/user is notified

Questions

  1. 1
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  2. 2
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  3. 3
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  4. 4
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