O Level / IGCSE Computer Science MCQs with answers
Practise O Level / IGCSE Computer Science (2210 / 0478) with 306 exam-style MCQs, each with the answer and a short explanation. Every test is marked the moment you finish and shows your score chapter by chapter, so you know what to revise next. It is free and needs no sign-up.
306 questions · 10 chapters
What each chapter covers 10 chapters
The questions follow the syllabus chapter by chapter. You can test the whole subject or one chapter at a time.
- Data representation 31 questionsNumber systems, Text, sound and images, Data storage and compression
- Data transmission 28 questionsTypes and methods of data transmission, Methods of error detection, Encryption
- Hardware 41 questionsComputer architecture, Input and output devices, Data storage, Network hardware
- Software 19 questionsTypes of software and interrupts, Types of programming language, translators and IDEs
- The internet and its uses 30 questionsThe internet and the world wide web, Digital currency, Cyber security
- Automated and emerging technologies 25 questionsAutomated systems, Robotics, Artificial intelligence
- Algorithm design and problem-solving 41 questionsProgram development life cycle and decomposition, Standard methods of solution, Validation, verification and test data, Trace tables and correcting algorithms
- Programming 43 questionsVariables, data types and operators, Sequence, selection, iteration and string handling, Procedures, functions and maintainable programs, Arrays and file handling
- Databases 20 questionsSingle-table databases and primary keys, Structured query language (SQL)
- Boolean logic 28 questionsLogic gates, Logic circuits and logic expressions, Truth tables
Sample O Level / IGCSE Computer Science MCQs with answers 12 questions
12 questions from the test, one or two from each chapter. Try each one, then open the answer.
1. A student halves the sample rate used to record a song. Which statement about the new recording is correct?
- A
it is more accurate and the file size doubles
- B
the file size is the same but the recording is less accurate
- C
the accuracy is the same but the file size halves
- D
it is less accurate and the file size roughly halves
Show answer
Answer: D. Taking half as many samples per second means half as much data and a less faithful copy of the original wave. Accuracy and file size both rise and fall with the sample rate.
2. A company encrypts customer data it sends over the internet. A hacker intercepts the transmission. Which statement is correct?
- A
the hacker cannot capture the data at all
- B
the data is deleted automatically when intercepted
- C
the hacker can read the data but cannot change it, because it is encrypted
- D
the hacker has the data but cannot understand it without the key
Show answer
Answer: D. Interception is still possible. Encryption means the captured data is ciphertext, which is useless without the decryption key.
3. A smartphone changes its screen from portrait to landscape when it is turned on its side. Which sensor detects this?
- A
proximity sensor
- B
magnetic field sensor
- C
accelerometer
- D
pressure sensor
Show answer
Answer: C. An accelerometer measures acceleration and the direction of gravity, so it can detect the orientation of the phone. A proximity sensor detects nearby objects, such as the user’s ear.
4. Which translator converts an assembly language program into machine code?
- A
compiler
- B
interpreter
- C
assembler
- D
linker
Show answer
Answer: C. An assembler translates assembly language mnemonics into machine code. Compilers and interpreters translate high-level languages.
5. What is the difference between the internet and the world wide web?
- A
they are two names for the same thing
- B
the internet is only used for email; the world wide web is used for everything else
- C
the world wide web is the physical cables and routers; the internet is the collection of websites
- D
the internet is the infrastructure; the world wide web is the web pages accessed using it
Show answer
Answer: D. The internet is the global network infrastructure. The world wide web is one service that uses it: the collection of web pages.
6. A robot vacuum cleaner stops before it hits a wall. Which of its components allows this?
- A
its mechanical framework
- B
a sensor that detects the obstacle, sending data to its microprocessor
- C
its rechargeable battery
- D
the actuator that turns the brushes and moves the robot across the floor
Show answer
Answer: B. Sensors (such as infra-red or proximity sensors) detect obstacles and send data to the microprocessor, which then controls the motors to stop or turn.
7. What is output by this algorithm?
X ← 1
Y ← 0
WHILE X < 20 DO
Y ← Y + X
X ← X * 3
ENDWHILE
OUTPUT Y
- A
13
- B
27
- C
40
- D
4
Show answer
Answer: A. Trace: X=1, Y=1, X=3; X=3, Y=4, X=9; X=9, Y=13, X=27; now X < 20 is false, so the loop ends and 13 is output. 40 wrongly adds 27 as well.
8. Which of these makes a program easier to maintain?
- A
using single-letter names such as X and Q for all variables
- B
writing the whole program as one long block of code
- C
using meaningful identifiers, comments and subroutines
- D
removing all indentation to make the code shorter
Show answer
Answer: C. Meaningful names, comments that explain the code, and procedures and functions make it easier for another programmer to understand and update.
9. Why is the field CustomerName not suitable as the primary key of a CUSTOMER table?
- A
names are too long to be stored
- B
names are stored as text, but a primary key must always be a numeric field such as an ID
- C
two customers can have the same name, so it may not be unique
- D
names cannot be searched with SQL
Show answer
Answer: C. A primary key must be unique for every record. A primary key does not have to be numeric; the problem is that names can repeat.
10. A logic gate symbol is drawn as a triangle with a small circle at its output. Which gate is it?
- A
AND
- B
NOT
- C
NOR
- D
XOR
Show answer
Answer: B. The NOT gate symbol is a triangle with a small circle (the inversion bubble) at the output. It is the only gate with one input.
11. Why do computers store and process all data, including text, sound and images, in binary?
- A
binary numbers always take up less storage space than the same values written in denary
- B
binary is the only number system that can store negative values
- C
binary is easier for programmers to read than hexadecimal
- D
their circuits are built from switches (transistors) that have only two states
Show answer
Answer: D. Logic gates and registers are made of transistors that are either on or off, so every form of data must be converted to 1s and 0s. Binary is not more compact than denary; it needs more digits.
12. Which is a benefit of the universal serial bus (USB) interface?
- A
a connected device is detected automatically and the correct driver is loaded
- B
USB cables can be several kilometres long
- C
USB sends data in parallel along many wires, so it is always the fastest interface available
- D
USB devices do not need a driver of any kind
Show answer
Answer: A. USB is a standard: devices are recognised automatically when plugged in and their drivers are loaded; the connector can also supply power. Cable length is limited to a few metres.
Try 294 more questions
Ways to practise 5 ways
- Quick check. 10 questions drawn fresh each time, about 10 minutes.
- By chapter. 10 questions from one chapter, for the topic you are revising now.
- Full paper. A full-length timed paper across the whole syllabus.
- Practice mode. See the right answer and an explanation after every question, with no clock.
- Exam mode. Timed like the real paper, with no going back.
Common questions
Is this O Level / IGCSE Computer Science test free?
Yes. Every test and every explanation is free, and you do not need an account. If you sign in, your results are kept across your devices.
Are these past paper questions?
The 306 MCQs are our own, written to the syllabus in the style of the exam.
How is the test marked?
Instantly. You get your score, the right answer and an explanation for every question, and a list of the topics to work on.
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