How computers represent data

How text, images and sound are turned into numbers so a computer can store and use them

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Try each question. If you're stuck, leave it and come back. The answer key is on the last page.

1
What number system do computers use at the very lowest level? A) Binary (0s and 1s) B) Decimal (0 to 9) C) Roman numerals D) English words
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2
True or false? Each letter, picture and sound is stored as numbers inside a computer. A) True B) False
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3
How is a digital image made up? A) A grid of tiny coloured dots called pixels B) A single big colour C) A long sentence D) A page of text
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4
In RGB colour, what do R, G and B stand for? A) Red, Green, Blue B) Round, Grey, Black C) Right, Glide, Below D) Real, Good, Best
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5
How is text stored in a computer? A) Each character has a number (for example, in ASCII A is 65) B) Each letter is photographed and stored as an image C) Each letter is stored as a sound D) Text is not stored at all
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6
In ASCII, the letter A has the value 65. What number does B have? If A is 65 in ASCII, B is ___ .
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7
True or false? In RGB, each colour value is usually between 0 and 255. A) True B) False
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8
Match each type of data to how a computer stores it. Match each item on the left to one on the right. Left: Text, Image, Sound, Whole number Right: Numbers (one per character, e.g. ASCII), Grid of pixels with colour values, Numbers sampling the wave over time, Binary digits (0s and 1s)
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9
How does a computer store sound? A) By taking lots of samples of the sound wave's loudness over time B) By taking a photograph of the speaker C) By writing down the song lyrics D) By guessing how loud it is
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10
Why is binary used in computers rather than decimal? A) Electronic circuits only have two reliable states: on and off B) Binary looks prettier C) Decimal numbers are illegal D) Computers were invented by people with 2 fingers
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Answer key

How computers represent data · for parents and teachers

1
Binary (0s and 1s)
Computers use binary - only 0s and 1s - because their circuits work in two states: on (1) and off (0).
2
True
Yes. Computers can only really store numbers. Letters, images and sounds are all turned into numbers so they can be stored.
3
A grid of tiny coloured dots called pixels
Digital images are made of pixels - tiny coloured squares in a grid. Each pixel has a colour, and the grid makes the picture.
4
Red, Green, Blue
RGB stands for Red, Green and Blue. Mixing these three colours of light in different amounts makes all other colours on screen.
5
Each character has a number (for example, in ASCII A is 65)
Codes like ASCII give every letter a number. A is 65, B is 66, and so on. The computer stores text as a list of these numbers.
6
66
ASCII gives letters numbers in order. A is 65, B is 66, C is 67, and so on.
7
True
Yes. Each of red, green and blue is usually a value from 0 (none) to 255 (maximum), giving lots of colours when combined.
8
Text → Numbers (one per character, e.g. ASCII); Image → Grid of pixels with colour values; Sound → Numbers sampling the wave over time; Whole number → Binary digits (0s and 1s)
Text uses character codes. Images use pixel colours. Sound uses samples. All are stored as numbers in binary inside the computer.
9
By taking lots of samples of the sound wave's loudness over time
A computer records the height of a sound wave (its amplitude) thousands of times a second. Each measurement is one number sample.
10
Electronic circuits only have two reliable states: on and off
Computer circuits work with electricity that is either on or off. Two values match up perfectly with binary's 0 and 1.