Lesson 4.5.6.2

4.5.6.2 Analogue and digital data and conversion Quiz: AQA Computer Science, Unit 5

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 4.5.6.2, Analogue and digital data and conversion: 20 multiple choice questions for the AQA Computer Science (7517), Unit 5: Fundamentals of data representation, written with Revision Ninja.

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The 20 questions

  1. What is analogue data?

    • Data that is always whole numbers
    • Data stored only as ASCII text
    • Data that varies continuously over a range of values
    • Data restricted to discrete values such as 0 and 1

  2. What is digital data?

    • Data sent only through analogue cables
    • Data that varies continuously, such as a sine wave
    • Data represented by discrete values, usually as binary digits
    • Data that cannot be stored

  3. What does an analogue to digital converter (ADC) do?

    • Converts digital data into an analogue signal
    • Stores digital data on a disk
    • Amplifies a digital signal without changing it
    • Converts an analogue signal into digital values

  4. What does a digital to analogue converter (DAC) do?

    • Compresses digital audio
    • Converts ASCII text into sound
    • Converts analogue sensor readings into digits
    • Converts digital values into an analogue signal

  5. What is the most common use of a DAC?

    • Recording a microphone signal in analogue form onto a magnetic tape for later playback
    • Converting a digital audio signal into an analogue signal for speakers
    • Converting an image into vector graphics so that it can be scaled without losing quality
    • Reading a temperature sensor and turning its analogue reading into a digital value

  6. Which kind of input is usually connected to an ADC?

    • A keyboard, which sends digital codes
    • An analogue sensor, such as a temperature sensor
    • A mouse that outputs digital coordinates
    • A printer that outputs digital text

  7. What is a signal in this context?

    • A compressed file that has been reduced in size by removing repeated data from the stream
    • A value stored only in ASCII text, with each character held as a single byte in memory
    • The physical representation of data that varies over time and can be transmitted
    • A list of pixels in an image, each holding a colour value for one position in the grid

  8. How many discrete levels can an 8-bit ADC output?

    • 64
    • 128
    • 255
    • 256

  9. An 8-bit ADC measures a 0 to 5 V range. What is the approximate size of one step?

    • About 0.0039 V, which is 1 V divided by 256 levels in the converter
    • About 0.1 V, which is the step size for a converter that uses only 50 levels
    • About 0.0195 V, which is 5 V divided by 256 levels
    • About 0.5 V, which is one tenth of the full five-volt range of the converter

  10. An analogue reading is sampled as 100 on a 0 to 255 scale. What is its 8-bit binary pattern?

    • 01100110
    • 01000100
    • 01100100
    • 10010000

  11. A DAC receives 00000000 and its full scale is 5 V for 11111111. What voltage is output?

    • 0 V
    • -5 V
    • 2.5 V
    • 5 V

  12. Why does a higher bit depth improve a DAC output?

    • More bits convert the signal into ASCII text
    • More bits reduce the sampling rate that is needed
    • More bits give more output levels, so the analogue signal is smoother
    • More bits make the output louder without any extra levels

  13. How many levels does a 12-bit ADC produce?

    • 1024
    • 2048
    • 4096
    • 12

  14. Which process converts a continuous light level into digital values?

    • Converting it into vector graphics
    • Sampling and quantising the level with an ADC
    • Sending it through a digital speaker
    • Decompressing it with a DAC

  15. How many bits does an ADC need to produce 256 distinct levels?

    • 7
    • 8
    • 9
    • 16

  16. Why does an ADC's resolution limit how accurately an analogue value is represented?

    • It limits only the sampling rate of the analogue signal, so the resolution of values is unaffected
    • It has no effect on accuracy because digital values are always exact once they have been stored
    • It only affects the sign of the value that is stored, so the size of the value is kept
    • Each output code covers a range of input voltages, so small differences within that range are lost

  17. Explain the difference between sampling rate and bit depth in digital conversion.

    • Sampling rate sets the size of each stored value, while bit depth sets how often values are taken
    • Bit depth affects only the speed at which the DAC converts values, not the detail of each level
    • Sampling rate sets how often the signal is measured, while bit depth sets how finely each measurement is described
    • They are the same measure expressed in two different units, so either can be used for both

  18. A DAC holds each digital value until the next sample arrives. Why does the output look stepped?

    • The steps are caused only by the amplifier, which adds small jumps to the output waveform
    • The steps come from the ASCII codes being read one character at a time by the converter
    • Each value is held constant until the next sample, which produces steps in the output
    • The DAC always outputs a perfect smooth curve, so no steps can appear in the final signal

  19. A 10-bit ADC covers an input range of 0 to 3.3 V. What is the approximate voltage per step?

    • About 3.2 mV
    • About 32 mV
    • About 0.3 mV
    • About 3.3 V

  20. Can a digital representation of an analogue signal ever be perfect?

    • Yes, provided the signal is sampled at any rate, because the converter then keeps all detail
    • No, sampling and quantisation always lose some information, though higher rates and depths reduce the loss
    • No, but only because digital signals cannot be stored in full on any storage medium available
    • Yes, digital data always matches the analogue signal exactly, since each value is stored as a number

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