ASCII is a character set that uses 7 bits to represent each character.
Give two limitations of 7-bit ASCII when it is used to represent text.
Mark scheme
Award one mark for any of the following up to a maximum of two marks:
- (Only) 128 different characters can be represented / 7 bits give 2^7 = 128 different codes (1)
- It cannot represent characters from languages other than English / non-English alphabets, e.g. Greek, Chinese (1)
- It cannot represent accented characters, e.g. é, ñ (1)
- It cannot represent symbols or emoji that are not in the ASCII character set (1)
Award a maximum of one mark for the last three bullets, as they are all examples of characters that fall outside the 128 ASCII codes.
Allow 'it can only represent 128 characters, so some characters are missing' for the first bullet.
Do not accept 'it uses 7 bits' / 'it only uses 7 bits' on its own, without saying what this limits.
Do not accept 'it can only store a limited amount of text' / 'it can only store short messages', as 7 bits limits the number of characters available, not the length of a message.
Do not accept 'it can only represent the characters in the ASCII character set', as this repeats the question.
Do not accept 'it is old/out of date' or 'it cannot store numbers'.
Example answers and how they were marked
Only 128 different characters can be represented, so it cannot store characters from other languages such as Greek.
Why: 128 character limit (1) and characters from other languages (1); two separate creditworthy limitations.
It cannot show accented characters like é and it only uses 7 bits.
Why: Accented characters (1); 'only uses 7 bits' is not qualified, so scores 0.
It only uses 7 bits, so it can only store a small amount of text.
Why: Scores 0: text length is not a limitation of 7-bit ASCII, and 'only uses 7 bits' is unqualified; both Do not accept lines apply.