AS Level Computer Science chapter 1: Information representation MCQs with answers

By Team Megalecture · Updated 4 Nov 2026

33 exam-style questions on Information 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.

33 questions · 3 topics · 10 per test

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What chapter 1 covers

Ten Information representation questions with answers

Try each one, then open the answer. These ten stay the same; the test draws new ones every time.

1. What is the hexadecimal number 3F in denary?

  1. A
    62
  2. B
    63
  3. C
    315
  4. D
    48
Show answer

Answer: B. 3 × 16 + 15 = 63 (F = 15). 315 comes from writing the digit values side by side instead of using place value.

2. How is the denary number 937 written in Binary Coded Decimal (BCD)?

  1. A
    0011 1010 1001
  2. B
    1001 0011 0111
  3. C
    1001 0011 1110
  4. D
    0111 0011 1001
Show answer

Answer: B. BCD codes each denary digit in its own 4-bit nibble: 9 = 1001, 3 = 0011, 7 = 0111. 0011 1010 1001 is the pure binary value of 937 (hex 3A9).

3. In ASCII, the character 'A' has the code 65 and the letters follow in order. What is the 7-bit ASCII code for 'D'?

  1. A
    1000100
  2. B
    1000011
  3. C
    1000101
  4. D
    0100100
Show answer

Answer: A. 'D' is three letters after 'A', so its code is 68 = 64 + 4 = 1000100. 1000011 is 67 ('C') and 1000101 is 69 ('E').

4. To work out 25 − 14 in 8-bit two's complement, a processor adds 00011001 to which binary number?

  1. A
    11110001
  2. B
    11110010
  3. C
    10001110
  4. D
    00001110
Show answer

Answer: B. Subtraction is done by adding the two's complement of 14: 00001110 → invert 11110001 → add 1 → 11110010. The sum 1 00001011 gives 11 once the carry is discarded.

5. A bitmap's width and height in pixels are both halved; the colour depth is unchanged. What happens to its file size?

  1. A
    it halves
  2. B
    it falls to a quarter
  3. C
    it is unchanged
  4. D
    it falls to an eighth
Show answer

Answer: B. The number of pixels is (½ × width) × (½ × height) = ¼ of the original, so the file is about a quarter of the size.

6. Why must a sound wave be sampled before it can be stored on a computer?

  1. A
    sound is analogue and must become discrete digital values
  2. B
    sampling removes the background noise from the sound
  3. C
    sound is digital and must be converted to analogue first
  4. D
    sampling compresses the sound so it will fit in memory
Show answer

Answer: A. Sound is a continuous analogue signal. Sampling measures its amplitude at regular intervals and stores each measurement as a binary number.

7. Why is lossy compression usually acceptable for photographs on a web page?

  1. A
    lossy compression keeps every pixel value exactly the same
  2. B
    files are far smaller and the lost detail is hardly seen
  3. C
    lossless compression methods cannot be used on images
  4. D
    lossy files can be re-saved many times with no further loss
Show answer

Answer: B. Lossy compression gives much smaller files that load quickly, and removes detail the eye hardly notices. Each re-save loses more data, so the last option is false.

8. Two 8-bit two's complement numbers, 01100100 and 00110010, are added. Which statement describes the 8-bit result?

  1. A
    10010110, which is the correct value of +150
  2. B
    00010110, with the carry out of the MSB ignored
  3. C
    10010110, an overflow, as the sign bit is now 1
  4. D
    11001000, a valid negative result in range
Show answer

Answer: C. 100 + 50 = 150, but the largest 8-bit two's complement value is +127. The sum 10010110 has a 1 in the sign bit, so two positives appear to give a negative: overflow.

9. How does lossy compression of a music file typically reduce its size?

  1. A
    it replaces repeated samples with a count and a value
  2. B
    it increases the sampling rate so fewer bits are needed
  3. C
    it stores the sound as a drawing list of objects and properties
  4. D
    it removes sounds people cannot hear or that are masked
Show answer

Answer: D. Perceptual coding discards frequencies outside human hearing and quiet sounds masked by louder ones at the same time. That data cannot be recovered.

10. A 10-second stereo (2-channel) clip is recorded at 44 100 samples per second with a 16-bit sampling resolution. What is its size?

  1. A
    882 000 bytes
  2. B
    14 112 000 bytes
  3. C
    3 528 000 bytes
  4. D
    1 764 000 bytes
Show answer

Answer: D. 44 100 × 16 × 2 × 10 = 14 112 000 bits ÷ 8 = 1 764 000 bytes. 882 000 forgets the second channel; 14 112 000 is the answer in bits.

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Ways to practise this chapter

Information representation: questions students ask

How many Information representation MCQs are there?

33, each with the answer and a short explanation, across 3 topics: Data representation, Multimedia, Compression. Every chapter test draws ten of them, so you can take it many times.

Is the AS Level 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.

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