GCSE-ready- Home
- Lessons
- KS3 Computing
- Representing text: ASCII and Unicode
Representing text: ASCII and Unicode
🎬 The doodle video for this lesson is coming soon. Subscribe on YouTube to see it first.
When you type a letter, the computer stores a number. A character set says which number stands for which character.
Character sets
A character set is a list of characters and the binary code for each one.
ASCII uses 7 bits, giving 2 × 2 × 2 × 2 × 2 × 2 × 2 = 128 characters: letters, digits, punctuation and some control codes.
Characters are often stored in one byte (8 bits) each.
ASCII uses 7 bits, giving 2 × 2 × 2 × 2 × 2 × 2 × 2 = 128 characters: letters, digits, punctuation and some control codes.
Characters are often stored in one byte (8 bits) each.
ASCII codes
Unicode
ASCII only covers English letters. Unicode is a much bigger character set. It includes the letters of many languages, such as Arabic, Chinese and Greek, as well as maths symbols and emoji.
Unicode uses more bits per character, so the same text can take up more space.
Unicode uses more bits per character, so the same text can take up more space.
How much space does the word HELLO take if each character uses 1 byte?
- HELLO has 5 characters.
- 5 × 1 byte = 5 bytes = 5 × 8 = 40 bits.
Answer: 5 bytes (40 bits)
A character set maps characters to binary codes. ASCII uses 7 bits for 128 characters (A = 65, a = 97). Unicode covers many languages and emoji, but uses more bits.
The interactive lesson includes the diagrams for this topic.
Check you have got it
Answer 6 quick questions with instant marking. If you get one wrong, GCSE-ready shows you why and gives you another go. It is free, and you do not need an account.