ASCII vs Unicode Comparison — Text, Sound and Images | IGCSE Computer Science

Exam Frequency Analysis

Past paper frequency (2018 to 2024)

This topic accounts for approximately 5% of your exam marks.

stable

Rare

Stable5%

ASCII/Unicode, sound sampling and pixel/colour depth appear regularly as 2 to 4 mark questions.

This comparison comes up almost every year. The mark scheme wants precise statements.

Feature	ASCII	Unicode
Bits per character	7 (or 8 for extended)	16+
Number of characters	128 (or 256)	65 536+
Storage space per character	Small	Large
Languages covered	English only	All major world languages
Emoji and modern symbols	No	Yes
Best use	English text on systems with limited memory	International text, web pages, modern software

Trade-offs in a single sentence

Unicode stores more characters but uses more memory per character.
ASCII uses less memory but cannot represent international text or emoji.

Mark-scheme language: when comparing, mention the number of bits, the number of characters, and what each can represent. Vague answers like "Unicode is bigger" or "Unicode is better" do not score.