O Level / IGCSE Computer Science chapter 3: Hardware MCQs with answers
By Team Megalecture · Updated 4 Nov 2026
41 exam-style questions on Hardware, each with the answer and a short explanation. Ten of them are below to try. The chapter test draws ten fresh questions each time and is marked the moment you finish, with your score by topic.
Try each one, then open the answer. These ten stay the same; the test draws new ones every time.
1. 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.
2. What is a microprocessor?
A
a very small computer program
B
the memory that holds the start-up instructions
C
a device that converts analogue signals from sensors into digital data
D
an integrated circuit on a single chip that can act as a CPU
Show answer
Answer: D. A microprocessor is a type of integrated circuit on a single chip. It processes instructions and data, as a CPU does.
3. What is the purpose of an actuator in a computer-controlled system?
A
to convert an electrical signal from the computer into physical movement
B
to measure a physical quantity, such as temperature, and send it to the computer
C
to store the readings taken by sensors
D
to convert analogue data into digital data
Show answer
Answer: A. An actuator is an output device, such as a motor or valve, that produces movement in response to a signal. Measuring quantities is the job of a sensor.
4. What is the role of the arithmetic logic unit (ALU)?
A
to carry out calculations and logical comparisons
B
to hold the address of the next instruction
C
to send control signals to the other components of the computer
D
to store programs that are not being used
Show answer
Answer: A. The ALU performs arithmetic (such as addition) and logic operations (such as comparisons). Sending control signals is the job of the control unit.
5. Why does a computer need ROM as well as RAM?
A
ROM is faster than RAM
B
ROM can store more data than RAM
C
the start-up instructions must be kept when the power is off, and RAM would lose them
D
ROM is used to store the user’s documents so they are not lost when the computer is switched off
Show answer
Answer: C. When the computer is switched on, RAM is empty. The instructions to start the computer are held in ROM because it is non-volatile.
6. Which of these is an example of solid-state storage?
A
hard disk drive (HDD)
B
DVD
C
Blu-ray disc
D
SD card
Show answer
Answer: D. An SD card is flash (solid-state) memory, like an SSD or a USB drive. An HDD is magnetic; DVD and Blu-ray are optical.
7. A computer with little RAM becomes very slow when many programs are open. Why?
A
pages are constantly swapped with virtual memory on much slower secondary storage
B
the cache has become full of documents
C
the ROM is being overwritten
D
the CPU clock speed is automatically reduced whenever more programs are open at the same time
Show answer
Answer: A. Virtual memory lets more programs run, but moving pages between RAM and much slower secondary storage takes time. Frequent swapping makes the computer slow.
8. What is meant by cloud storage?
A
storage on a USB flash drive that can be carried around and moved between computers
B
data held in RAM while a program is running
C
data stored on remote physical servers and accessed over the internet
D
virtual memory created on the hard disk
Show answer
Answer: C. Cloud storage keeps data on physical servers owned by a provider and accessed remotely through the internet, rather than locally on the user’s device.
9. Which statement describes a typical embedded system?
A
it is used for many different tasks chosen by the user
B
it always has a large screen and a keyboard
C
it runs a range of application software installed by the user
D
it performs a dedicated function within a larger device
Show answer
Answer: D. An embedded system does one job, often with little or no user interface, and is usually small, low-power and cheap to make. General-purpose computers run many applications.
10. How does optical storage such as a Blu-ray disc store data?
A
as pits and lands that are created and read using a laser
B
as magnetised regions on the surface that are read by an electromagnet
C
as charge stored in NAND flash memory
D
as holes punched in the disc
Show answer
Answer: A. Optical media use a laser to create and read pits and lands on the disc surface. CD, DVD and Blu-ray are all optical.
41, each with the answer and a short explanation, across 4 topics: Computer architecture, Input and output devices, Data storage, Network hardware. Every chapter test draws ten of them, so you can take it many times.
Is the O Level / IGCSE Computer Science chapter 3 test free?
Yes. The test, the answers and the explanations are free and need no sign-up. Sign in only if you want your scores kept across devices.
How is the chapter test marked?
The moment you press Finish: your score, the right answer and an explanation for every question, and the ones you got wrong saved in My mistakes to retry.
