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Lesson 2 of 8
  • OCR

Representing text using ASCII and Unicode

I can explain how computers represent text.

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View unit
Lesson 2 of 8
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New
  • OCR

Representing text using ASCII and Unicode

I can explain how computers represent text.

Download all

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Lesson details

Key learning points

  1. The number of possible states of a sequence of n bits is 2 raised to the power of n.
  2. A character set is a record of characters, each matched to a unique binary sequence.
  3. ASCII character representation uses an 8-bit binary sequence to represent each character.
  4. Unicode character representation uses up to 32 bits to represent each character.
  5. The first 256 characters of Unicode are the same as in ASCII.

Keywords

  • State - value of data at a specific point in time

  • Character set - a record of characters matched to a unique binary sequence

  • ASCII - a character set that represents each character with a unique numerical value

  • Unicode - a method of character representation that uses up to 32 bits per character

Common misconception

ASCII and Unicode are only used to represent the characters and symbols found in written communication across all languages in the world.

ASCII and Unicode include more than just characters from written languages. ASCII represents English letters, numbers and symbols. Unicode supports other symbols beyond written text, including mathematical symbols, emojis and non-text elements.

Use Python to explore the conversion of characters from character codes to the represented characters. Pupils could create secret ASCII messages to pass along for others to decode.
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Licence

This content is © Oak National Academy Limited (2025), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

Lesson video

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Prior knowledge starter quiz

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6 Questions

Q1.
How many bits are there in a byte?

Correct Answer: 8, eight

Q2.
What is the smallest unit of data in a computer?

Correct Answer: bit, a bit

Q3.
Arrange the following in order of increasing bits:

1 - bit
2 - byte
3 - kilobyte

Q4.
What is the purpose of binary sequences in computers?

to represent text only
to represent images only
to represent audio only
Correct answer: to represent all data and instructions that computers process

Q5.
What is the next binary number after 111?

Correct Answer: 1000

Q6.
What is the binary equivalent of the decimal number 10?

Correct Answer: 1010

Assessment exit quiz

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6 Questions

Q1.
Match the following terms to their definitions.

Correct Answer:ASCII,a method of character representation using 8 bits

a method of character representation using 8 bits

Correct Answer:Unicode,a method of character representation using up to 32 bits

a method of character representation using up to 32 bits

Correct Answer:character set,a record of characters, each matched to a unique binary sequence

a record of characters, each matched to a unique binary sequence

Correct Answer:bit,smallest unit of data

smallest unit of data

Correct Answer:byte,8 bits together

8 bits together

Q2.
How many different values can be represented by a 3-bit binary number?

Correct Answer: 8, eight

Q3.
If the ASCII value of 'A' is 65 in decimal, what is the ASCII value of 'C' in decimal?

Correct Answer: 67

Q4.
Why might we need more than just ASCII for character representation?

to only represent English characters
to simplify binary sequences
Correct answer: to support other symbols beyond written text

Q5.
How does Unicode differ from ASCII?

Correct answer: Unicode uses more bits for character representation.
Unicode is only for English characters.
ASCII uses more bits than Unicode.
They are identical.

Q6.
What is the relationship between ASCII and Unicode?

They are completely different.
Correct answer: The first 256 characters of Unicode are the same as in ASCII.
Unicode does not include any ASCII characters.

Lesson appears in

UnitComputing / Representation of text, images and sound

OCRComputing

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