IGCSE Computer Science 0478 · Topic 3

Describe how a check digit is used to detect: past paper questions

190 real questionsasked in 10 of the last 10 exam series2019–2026usually: Identify, Give, Explain, Describe, State

Real questions on describe how a check digit is used to detect

The newest 20 of 190 written questions. Open one to see it on the real paper.

0478/11 · May/June 2026 · Q7a[1]
Give one suitable sensor that the robot animal could use to identify a clapping sound.
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0478/11 · May/June 2026 · Q7b[2]
Give two suitable sensors that the robot animal could use to identify if an object is nearby.
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0478/12 · May/June 2026 · Q1a[1]
Tick (3) one box to show whether a microphone is an input, output, process or storage device. A input B output C process
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0478/12 · May/June 2026 · Q1d[1]
Identify one example of a sensor that would be built into the smartwatch.
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0478/12 · May/June 2026 · Q2a[1]
State the role of the CPU.
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0478/12 · May/June 2026 · Q2b[2]
The memory address register (MAR) and the memory data register (MDR) are two registers built into the CPU. Give two other registers that are built into the CPU.
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0478/12 · May/June 2026 · Q2c[3]
Explain how the MAR and MDR are used in this process. (c) A value is fetched from random access memory (RAM) to the CPU.
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0478/12 · May/June 2026 · Q2d[3]
The CPU has a clock speed of 3 GHz. Describe what is meant by a 3 GHz clock speed.
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0478/12 · May/June 2026 · Q3f(i)[2]
One feature of magnetic storage is that it has moving parts. Give two other features of magnetic storage.
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0478/12 · May/June 2026 · Q3f(ii)[1]
The video streaming service wants faster read and write speeds for their videos than is provided by magnetic storage. State which type of storage they should use.
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0478/13 · May/June 2026 · Q3a(i)[1]
Give the name of the input device built into the tablet computer that is used to record the sound produced by the piano.
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0478/13 · May/June 2026 · Q3a(ii)[1]
Identify one other input device that can be built into the tablet computer. (ii)
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0478/13 · May/June 2026 · Q3a(iii)[1]
The tablet computer has a display screen to output data for the student. Give one other output device that can be built into the tablet computer.
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0478/13 · May/June 2026 · Q3c(i)[1]
Instructions are fetched from random access memory (RAM) into the processor. The control unit uses a list to decode the instructions into commands that can be processed. Give the name of the list that is used for this purpose.
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0478/13 · May/June 2026 · Q3c(ii)[4]
The student wants a new tablet computer that has a 2.4 GHz dual-core processor. Explain whether the processor of the new tablet computer would have a better performance than the processor of her current tablet computer.
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0478/13 · May/June 2026 · Q3d[2]
The tablet computer has a built-in biometric device. Explain the purpose of the biometric device.
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0478/13 · May/June 2026 · Q4[3]
A computer has a central processing unit (CPU). Identify three components that are built into a CPU from the given list. accumulator (ACC) binary counter (BC) binary register (BR) binary unit (BU) current instruction register (CIR) instruction unit (IU) program counter (PC) read only memory (ROM)
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0478/13 · May/June 2026 · Q8c[3]
A microprocessor is used to find out whether a user has input the correct 3-digit denary number. Explain the role of the microprocessor in this process.
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0478/21 · May/June 2026 · Q5b[3]
The last name is input into the variable LastName Write the pseudocode to: • • • take the first two letters from LastName convert the letters to upper case store the result in the variable Temp
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0478/22 · May/June 2026 · Q6a[1]
Complete the trace table for the algorithm, using the input data: post, Y, committee, N, bookkeeper Note: the first character of each word is in position 1. Word WordLength Count NumLetter Choice OUTPUT
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What examiners said

Comprehensive responses • Many candidates identified one characteristic of secondary storage. Limited responses • Some candidates gave a comparison between primary and secondary storage or a benefit of secondary storage. • Some candidates identified a larger storage capacity than primary, which is not always accurate depending on the devices.
— Examiner report, February/March 2026, 0478/12 Q5(a) (Cambridge)

Comprehensive responses • Most candidates identified the correct tern for at least one space. Limited responses • Some candidates identified XOR gates instead of NOR gates. • Some candidates identified pits and lands instead of electromagnetic field.
— Examiner report, February/March 2026, 0478/12 Q5(b) (Cambridge)

Comprehensive responses • Many candidates were able to describe several parts of the process, giving a logically ordered description of the stages. Limited responses • Some candidates described an echo check and that the sender resends the data after they have compared the two sets of data • Some candidates described the process of positive acknowledge without mentioning negative acknowledgements...
— Examiner report, February/March 2026, 0478/12 Q7(c)(ii) (Cambridge)

Practise this topic

Answer these questions online and get each one marked against the official mark scheme, with what you missed and how to fix it.

Practise describe how a check digit is used to detect

In the syllabus

1 0478.3.0.01 — Describe how an automatic repeat query (ARQ) • Including the use of:

Describe how an automatic repeat query (ARQ) • Including the use of:
– positive/negative acknowledgements
– timeout
Explain the purpose and functions of a web • The main purpose of a web browser is to
render hypertext markup language (HTML) and display web pages • Functions include: – storing bookmarks and favourites – recording user history – allowing use of multiple tabs – storing cookies – providing navigation tools – providing an address bar
(a) Understand and use the concept of
Understand and use the concept of • Including:
– IF statements – CASE statements
Understand and use the concept of • Including:
– count-controlled loops – pre-condition loops – post-condition loops
Understand and use the concepts of
Understand and use the concept of string • Including:

2 0478.3.0.02 — – positive/negative acknowledgements

– positive/negative acknowledgements

3 0478.3.0.03 — – timeout

– timeout

4 0478.3.0.04 — Explain the purpose and functions of a web • The main purpose of a web browser is to

Explain the purpose and functions of a web • The main purpose of a web browser is to

5 0478.3.0.05 — render hypertext markup language (HTML) and display web pages • Functions include: – storing bookmarks and favourites – recording user histo

render hypertext markup language (HTML) and display web pages • Functions include: – storing bookmarks and favourites – recording user history – allowing use of multiple tabs – storing cookies – providing navigation tools – providing an address bar

6 0478.3.0.06 — (a) Understand and use the concept of

(a) Understand and use the concept of

7 0478.3.0.07 — Understand and use the concept of • Including:

Understand and use the concept of • Including:

8 0478.3.0.08 — – IF statements – CASE statements

– IF statements – CASE statements

9 0478.3.0.09 — Understand and use the concept of • Including:

Understand and use the concept of • Including:

10 0478.3.0.10 — – count-controlled loops – pre-condition loops – post-condition loops

– count-controlled loops – pre-condition loops – post-condition loops

11 0478.3.0.11 — Understand and use the concepts of

Understand and use the concepts of

12 0478.3.0.12 — Understand and use the concept of string • Including:

Understand and use the concept of string • Including:

13 0478.3.0.13 — – length – substring – upper – lower • The first character of the string can be position zero or one

– length – substring – upper – lower • The first character of the string can be position zero or one

14 0478.3.0.14 — Read, understand and complete structured • Limited to:

Read, understand and complete structured • Limited to:

15 0478.3.0.15 — – SELECT

– SELECT

16 0478.3.0.16 — – FROM – WHERE – ORDER BY DESCENDING – ORDER BY ASCENDING – SUM – COUNT – AND – OR • Identifying the output given by an SQL statement that w

– FROM – WHERE – ORDER BY DESCENDING – ORDER BY ASCENDING – SUM – COUNT – AND – OR • Identifying the output given by an SQL statement that will query the given contents of a database table

17 0478.3.1.01 — (a) Understand the role of the central • The CPU processes instructions and data that

(a) Understand the role of the central • The CPU processes instructions and data that
are input into the computer so that the result can be output
Understand what is meant by a • A microprocessor is a type of integrated circuit
on a single chip
(a) Understand the purpose of the • Including:
– units: arithmetic logic unit (ALU) and control
unit (CU) – registers: program counter (PC), memory address register (MAR), memory data register (MDR), current instruction register (CIR) and accumulator (ACC) – buses: address bus, data bus and control bus
Describe the process of the • How instructions and data are fetched from
random access memory (RAM) into the CPU,
how they are processed using each component
and how they are then executed • Storing data and addresses into specific registers • Using buses to transmit data, addresses and signals • Using units to fetch, decode and execute data and instructions
Understand what is meant by a core, cache • The number of cores, size of the cache and

18 0478.3.1.02 — are input into the computer so that the result can be output

are input into the computer so that the result can be output

19 0478.3.1.03 — Understand what is meant by a • A microprocessor is a type of integrated circuit

Understand what is meant by a • A microprocessor is a type of integrated circuit

20 0478.3.1.04 — on a single chip

on a single chip

21 0478.3.1.05 — (a) Understand the purpose of the • Including:

(a) Understand the purpose of the • Including:

22 0478.3.1.06 — – units: arithmetic logic unit (ALU) and control

– units: arithmetic logic unit (ALU) and control

23 0478.3.1.07 — unit (CU) – registers: program counter (PC), memory address register (MAR), memory data register (MDR), current instruction register (CIR) a

unit (CU) – registers: program counter (PC), memory address register (MAR), memory data register (MDR), current instruction register (CIR) and accumulator (ACC) – buses: address bus, data bus and control bus

24 0478.3.1.08 — Describe the process of the • How instructions and data are fetched from

Describe the process of the • How instructions and data are fetched from

25 0478.3.1.09 — random access memory (RAM) into the CPU,

random access memory (RAM) into the CPU,

26 0478.3.1.10 — how they are processed using each component

how they are processed using each component

27 0478.3.1.11 — and how they are then executed • Storing data and addresses into specific registers • Using buses to transmit data, addresses and signals •

and how they are then executed • Storing data and addresses into specific registers • Using buses to transmit data, addresses and signals • Using units to fetch, decode and execute data and instructions

28 0478.3.1.12 — Understand what is meant by a core, cache • The number of cores, size of the cache and

Understand what is meant by a core, cache • The number of cores, size of the cache and

29 0478.3.1.13 — speed of the clock can affect the performance

speed of the clock can affect the performance

30 0478.3.1.14 — of a CPU

of a CPU

31 0478.3.1.15 — Understand the purpose and use of an • An instruction set is a list of all the commands

Understand the purpose and use of an • An instruction set is a list of all the commands

32 0478.3.1.16 — that can be processed by a CPU, and the commands are machine code

that can be processed by a CPU, and the commands are machine code

33 0478.3.1.17 — Describe the purpose and characteristics of • An embedded system is used to perform a

Describe the purpose and characteristics of • An embedded system is used to perform a

34 0478.3.1.18 — dedicated functions

dedicated functions

35 0478.3.1.19 — For example in, domestic

For example in, domestic

36 0478.3.1.20 — appliances, cars, security systems, lighting systems or vending machines

appliances, cars, security systems, lighting systems or vending machines

37 0478.3.1.21 — This is different to a general purpose computer that is used to perform many different functions

This is different to a general purpose computer that is used to perform many different functions

38 0478.3.1.22 — For example in, a personal computer (PC) or a laptop

For example in, a personal computer (PC) or a laptop

39 0478.3.2.01 — Understand what is meant by an input device • Including:

Understand what is meant by an input device • Including:
– barcode scanner – digital camera – keyboard – microphone – optical mouse – QR code scanner – touch screen (resistive, capacitive and infra-red) – two-dimensional (2D) and three-dimensional (3D) scanners
Understand what is meant by an output device • Including:
– actuator – digital light processing (DLP) projector – inkjet printer – laser printer – light emitting diode (LED) screen – liquid crystal display (LCD) projector – liquid crystal display (LCD) screen – speaker – 3D printer
(a) Understand what is meant by a sensor and • Limited to:
– acoustic – accelerometer – flow – gas – humidity – infra-red – level – light – magnetic field – moisture – pH – pressure – proximity – temperature
Identify the type of data captured by each

40 0478.3.2.02 — – barcode scanner – digital camera – keyboard – microphone – optical mouse – QR code scanner – touch screen (resistive, capacitive and infra

– barcode scanner – digital camera – keyboard – microphone – optical mouse – QR code scanner – touch screen (resistive, capacitive and infra-red) – two-dimensional (2D) and three-dimensional (3D) scanners

41 0478.3.2.03 — Understand what is meant by an output device • Including:

Understand what is meant by an output device • Including:

42 0478.3.2.04 — – actuator – digital light processing (DLP) projector – inkjet printer – laser printer – light emitting diode (LED) screen – liquid crystal

– actuator – digital light processing (DLP) projector – inkjet printer – laser printer – light emitting diode (LED) screen – liquid crystal display (LCD) projector – liquid crystal display (LCD) screen – speaker – 3D printer

43 0478.3.2.05 — (a) Understand what is meant by a sensor and • Limited to:

(a) Understand what is meant by a sensor and • Limited to:

44 0478.3.2.06 — – acoustic – accelerometer – flow – gas – humidity – infra-red – level – light – magnetic field – moisture – pH – pressure – proximity – tem

– acoustic – accelerometer – flow – gas – humidity – infra-red – level – light – magnetic field – moisture – pH – pressure – proximity – temperature

45 0478.3.2.07 — Identify the type of data captured by each

Identify the type of data captured by each

46 0478.3.3.01 — Understand what is meant by primary storage • Primary storage is directly accessed by the CPU • Including the role of: – random access memor

Understand what is meant by primary storage • Primary storage is directly accessed by the CPU • Including the role of: – random access memory (RAM) – read only memory (ROM) • Including why a computer needs both RAM and ROM, and the difference between them
Understand what is meant by secondary • Secondary storage is not directly accessed by
the CPU and is necessary for more permanent storage of data
Describe the operation of magnetic, optical • Magnetic storage uses platters which are
divided into tracks and sectors
Data is read
and written using electromagnets
Including hard disk drive (HDD) • Optical storage uses lasers to create and read pits and lands
Including: CD, DVD and Blu-ray • Solid-state (flash memory) uses NAND or NOR technology
Transistors are used as control gates and floating gates
Including: solid-state drive (SSD), SD card and USB drive
Describe what is meant by virtual memory, how • Pages of data are transferred between RAM

47 0478.3.3.02 — Understand what is meant by secondary • Secondary storage is not directly accessed by

Understand what is meant by secondary • Secondary storage is not directly accessed by

48 0478.3.3.03 — the CPU and is necessary for more permanent storage of data

the CPU and is necessary for more permanent storage of data

49 0478.3.3.04 — Describe the operation of magnetic, optical • Magnetic storage uses platters which are

Describe the operation of magnetic, optical • Magnetic storage uses platters which are

50 0478.3.3.05 — divided into tracks and sectors

divided into tracks and sectors

51 0478.3.3.06 — Data is read

Data is read

52 0478.3.3.07 — and written using electromagnets

and written using electromagnets

53 0478.3.3.08 — Including hard disk drive (HDD) • Optical storage uses lasers to create and read pits and lands

Including hard disk drive (HDD) • Optical storage uses lasers to create and read pits and lands

54 0478.3.3.09 — Including: CD, DVD and Blu-ray • Solid-state (flash memory) uses NAND or NOR technology

Including: CD, DVD and Blu-ray • Solid-state (flash memory) uses NAND or NOR technology

55 0478.3.3.10 — Transistors are used as control gates and floating gates

Transistors are used as control gates and floating gates

56 0478.3.3.11 — Including: solid-state drive (SSD), SD card and USB drive

Including: solid-state drive (SSD), SD card and USB drive

57 0478.3.3.12 — Describe what is meant by virtual memory, how • Pages of data are transferred between RAM

Describe what is meant by virtual memory, how • Pages of data are transferred between RAM

58 0478.3.3.13 — and virtual memory when needed

and virtual memory when needed

59 0478.3.3.14 — Understand what is meant by cloud storage • Cloud storage can be accessed remotely in comparison to storing data locally

Understand what is meant by cloud storage • Cloud storage can be accessed remotely in comparison to storing data locally

60 0478.3.3.15 — Explain the advantages and disadvantages • Physical servers and storage are needed to

Explain the advantages and disadvantages • Physical servers and storage are needed to

61 0478.3.3.16 — store data in cloud storage

store data in cloud storage

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