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We’re refreshing the questions on our KS3 and GCSE Computer Science subject knowledge assessment. The current version remains available. Updated questions will be available from 18 May 2026.

GCSE

Lesson 9 Unicode and file size calculation

Curriculum > KS4 > Unit > Lesson

The lesson begins with revisiting ASCII and its limitations, namely that it can only represent 128 characters. You will then introduce Unicode as an alternative for a more universal character set. Learners will then calculate the number of bits that are needed to store a piece of text using ASCII and Unicode.

Learning objectives

  • Explain the need for Unicode
  • State that Unicode uses the same codes as ASCII up to 127
  • Calculate the number of bytes needed to store a piece of text

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