O Level / IGCSE Computer Science chapter 1: Data representation MCQs with answers
By Team Megalecture · Updated 4 Nov 2026
31 exam-style questions on Data representation, 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 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. 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.
3. Which list shows units of data storage in order of increasing size?
A
kibibyte, gibibyte, mebibyte, tebibyte
B
mebibyte, kibibyte, gibibyte, pebibyte
C
tebibyte, gibibyte, mebibyte, kibibyte
D
kibibyte, mebibyte, gibibyte, tebibyte
Show answer
Answer: D. Each unit is 1024 times the previous one: KiB, MiB, GiB, TiB, then PiB and EiB.
4. What is meant by the sample rate of a sound recording?
A
the number of bits that are used to store the value of each sample
B
the length of the recording in seconds
C
the loudness of the sound when it is played back
D
the number of samples of the sound wave taken each second
Show answer
Answer: D. Sample rate is samples per second (measured in hertz). The number of bits per sample is the sample resolution, a separate idea.
5. Which compression method is lossless?
A
reducing the sample rate of a sound file
B
reducing the colour depth of an image
C
reducing the resolution of an image
D
run length encoding (RLE)
Show answer
Answer: D. RLE stores runs of repeated data as a count and a value, and the original can be rebuilt exactly. The other three permanently remove data, so they are lossy.
6. What is the hexadecimal value 2F4A written as a 16-bit binary number?
A
0010 1111 0100 1100
B
0010 1110 0100 1010
C
0100 1111 0010 1010
D
0010 1111 0100 1010
Show answer
Answer: D. Convert each hex digit to 4 bits: 2 = 0010, F = 1111, 4 = 0100, A = 1010. The other options mis-convert A or F, or swap the 2 and 4.
7. The 8-bit register holds 1011 0101 (denary 181). A logical right shift of three places is performed. What does the register now hold?
A
1010 1000
B
0001 0110
C
0001 0111
D
1111 0110
Show answer
Answer: B. Shifting right 3 places moves every bit 3 places to the right; the three least significant bits (101) are lost and zeros enter on the left: 0001 0110 = 22. 181 ÷ 8 = 22.625, so the fraction is lost.
8. What is a character set?
A
the set of fonts and text styles that are installed on a computer for use in documents
B
the rules used to compress a text file
C
the keys available on a keyboard
D
a list of characters a computer can represent, each with a unique binary code
Show answer
Answer: D. A character set such as ASCII or Unicode gives every character it contains a unique binary code, so text can be stored and processed as binary.
9. A sound is recorded for 60 seconds at a sample rate of 16 000 samples per second and a sample resolution of 16 bits. What is the file size in KiB?
A
1920 KiB
B
15 000 KiB
C
1875 KiB
D
234.375 KiB
Show answer
Answer: C. 16 000 × 16 × 60 = 15 360 000 bits. ÷ 8 = 1 920 000 bytes. ÷ 1024 = 1875 KiB. 1920 uses 1000 instead of 1024; 15 000 forgets to divide by 8.
10. The positive binary integer 0001 0110 is given a logical left shift of two places. What is the result, and what is its effect?
A
0101 1000; the value is multiplied by 4
B
0000 0101; the value is divided by 4
C
0101 1000; the value is multiplied by 2
D
1001 0110; the value is increased by 128
Show answer
Answer: A. Each left shift multiplies by 2, so two places multiply by 4: 22 × 4 = 88 = 0101 1000. Zeros are shifted in on the right.
31, each with the answer and a short explanation, across 3 topics: Number systems, Text, sound and images, Data storage and compression. Every chapter test draws ten of them, so you can take it many times.
Is the O Level / IGCSE Computer Science chapter 1 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.
