This key facts covers Extended ASCII (8-bit) within Character Sets for GCSE Computer Science. Revise Character Sets in 3.3 Data Representation for GCSE Computer Science with 15 exam-style questions and 18 flashcards. This topic appears less often, but it can still be a useful differentiator on mixed-topic papers. It is section 4 of 11 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.
Extended ASCII (8-bit)
The 8-bit Expansion:
- 8 bits: 2⁸ = 256 possible characters (0-255)
- Codes 0-127: Same as standard ASCII (backward compatible)
- Codes 128-255: Extended characters (accented letters, symbols, box-drawing)
- Problem: Different "code pages" for different languages (no universal standard!)
Extended ASCII Characters (128-255):
- Accented letters: é (130), ñ (164), ü (129)
- Currency symbols: £ (156), ¥ (157), ¢ (155)
- Box-drawing: ─ │ ┌ ┐ └ ┘
- Math symbols: ± × ÷ ≈
The Extended ASCII Problem:
Code 130 might mean 'é' in Western Europe, but 'â' in Central Europe, or 'ב' in Hebrew. Files became unreadable when moved between systems. Unicode solved this chaos!
Practice questions for Character Sets
How many bits does standard ASCII use to represent each character?
Explain why using Unicode to store a text file produces a larger file than using ASCII to store the same text.