Lesson T4.3.1

T4.3.1 Representing text, sound and pictures digitally Quiz: KS3 Computing, Unit 4

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

In partnership with Revision Ninja

Lesson T4.3.1, Representing text, sound and pictures digitally: 20 multiple choice questions for the KS3 Computing (National Curriculum), Unit 4: Computer systems, written with Revision Ninja.

Host it live on the board and students join with a game code on their own devices, or revise alone with Free Play. The answers are revealed in the game.

Host this setFree Play

The 20 questions

  1. Why do computers store all data as binary digits?

    • Decimal numbers cannot be stored in memory because they use too many symbols
    • Electronic circuits can reliably represent two states, such as on and off
    • Binary is the only number system that a human being is able to read and write
    • Binary takes up more space than any other system, so files stay safe from damage

  2. How many bits are there in one byte?

    • 10
    • 4
    • 8
    • 16

  3. How many different values can 4 bits represent?

    • 8
    • 32
    • 4
    • 16

  4. What is ASCII used for?

    • Recording sound at a fixed number of samples per second for digital playback
    • Representing text characters as numbers, such as 65 for the capital letter A
    • Compressing photographs so that they take up less storage space on a device
    • Sending packets of data between routers across the wide area network

  5. Why does Unicode exist alongside ASCII?

    • It can represent characters from many languages and a much wider range of symbols
    • It removes the need for a computer to store any text at all on its hard drive
    • It makes all text in a document appear in the same font on every type of screen
    • It reduces the number of bits needed for every character to only three bits each

  6. A bitmap image is 100 pixels wide and 50 pixels high, and each pixel uses 8 bits. How many bits does the image need?

    • 40,000 bits
    • 400 bits
    • 80,000 bits
    • 5,000 bits

  7. Which setting most affects the quality of a bitmap image?

    • The number of pixels in the image, which is its resolution
    • The name of the file, which tells the viewer what the picture shows
    • The speed of the monitor on which the picture is displayed by the user
    • The date the picture was taken, which is stored in the file's header

  8. What is colour depth in a bitmap image?

    • The total number of pixels arranged in each row of the bitmap image on screen
    • The amount of time it takes for the image to load on a screen or a web page
    • The number of bits used to store the colour of each pixel
    • The number of colours printed on each page when the image is output by a printer

  9. What does a sampling rate describe in digital sound?

    • The number of different musical notes that can be produced by a single instrument
    • How many times per second the sound wave is measured when it is converted to digital form
    • The volume of the sound, measured in decibels as it is played through a speaker
    • The total length of the sound file, measured in minutes from start to finish

  10. A mono sound lasts 10 seconds, is sampled 1,000 times per second, and each sample uses 8 bits. How many bits does it need?

    • 80,000 bits
    • 10,000 bits
    • 800,000 bits
    • 8,000 bits

  11. What happens to the quality of digital sound when the bit depth is increased?

    • The sound is always converted into text, so it can be searched by the user later
    • The sampling rate falls to match the new bit depth without any change to the sound
    • The range of volume levels that can be represented becomes greater and more precise
    • The file becomes smaller, because each sample is stored with fewer bits than before

  12. Why must a sound wave be converted before a computer can store it?

    • A sound wave contains no energy, so the computer must add energy before it is stored
    • A sound wave is continuous and must be sampled and converted into discrete digital values
    • A sound wave cannot be heard by a computer, so it must be turned into text first
    • A sound wave can only be stored as an image, so it must be converted into pixels

  13. Which statement about vector images is correct?

    • They are made from a fixed grid of pixels, so they lose quality when enlarged
    • They store every colour of every pixel in the image, so they are always large files
    • They are made from mathematical shapes, so they can be scaled without losing sharpness
    • They can only show black and white, because the colours are stored as a single bit

  14. What does the term 'lossy compression' mean?

    • Some data is permanently removed to make the file smaller, which may reduce quality
    • The file is stored in a second location so that it cannot be lost if a device fails
    • The file is made smaller without losing any data, so it can always be restored exactly
    • The file is encrypted, so that anyone who does not have a key cannot read the contents

  15. Why are text characters stored as binary numbers in a computer?

    • Each character is recorded in the network router, which then sends it to the screen
    • Each character is stored in the processor's clock, which counts the letters typed
    • Each character is given a numeric code, and that code is held as binary digits
    • Each character is drawn as a picture of a letter, and the picture is then stored as bits

  16. What is the denary value of the binary number 1010?

    • 10
    • 14
    • 12
    • 8

  17. Which unit is the largest of these?

    • Byte
    • Megabyte
    • Gigabyte
    • Kilobyte

  18. A pupil wants to store a photo taken on a phone. Why might the photo file be large?

    • It contains only one colour, which makes the file take up more storage than normal
    • It has many pixels, each with colour information stored in several bits
    • It has been compressed using lossless compression, which always increases file size
    • It has been sent over the network, which always adds extra data to every image file

  19. Which statement about representing pictures digitally is correct?

    • A picture is stored as a single number that represents the average colour of the image
    • A picture is stored as a series of spoken instructions that the computer reads aloud
    • A picture is stored as a list of words describing what each part of it looks like
    • A picture is stored as a grid of pixels, each with a binary value for its colour

  20. Which image format uses lossless compression?

    • MPEG
    • MP3
    • PNG
    • JPEG

All KS3 Computing quizzes