The ASCII code for the character D is 68, which is stored as 01000100 in 8-bit ASCII.
(a) State the 8-bit binary code for the character G. [1]
(b) State what is meant by a character set. [1]
(c) A text file contains 2 000 characters. Calculate the size of the file, in kilobytes, if each character is stored using 16-bit Unicode. Show your working. [2]
(d) Explain why Unicode is used instead of ASCII for a website that is read in many countries. [1]
- (a) 01000111 (G is 3 after D, so 68 + 3 = 71); must be 8 bits as the question asks – do not accept 1000111(1)
- (b) A defined list of characters that a computer can recognise / represent, each with its own unique binary code; accept either idea on its own, e.g. 'all the characters a computer can represent' or 'a list of characters and the binary code for each'; reject 'the alphabet' / 'a font' on its own(1)
- (c) 2000 × 16 (= 32 000 bits); allow 2000 × 2 bytes (= 4 000 bytes)(1)
- (c) ÷ 8 ÷ 1000 = 4 KB; allow 3.90625 KB / 3.9 KB (dividing by 1024); correct answer with no working scores 2(1)
- (d) Unicode can represent characters from many different languages / alphabets (e.g. Chinese, Arabic) whereas ASCII can represent only a small set of characters (mainly English); allow Unicode uses more bits per character so it can represent many more characters, if linked to other languages / countries; do not accept 'Unicode is faster'(1)
- Answer: (a) 01000111 (b) A defined list of characters with a unique binary code for each (c) 4 KB (allow 3.9 KB) (d) Unicode can represent characters from all languages
- Examiner tip: Letters of the alphabet have consecutive codes: G is three letters after D, so its code is 68 + 3 = 71, written as 8 bits.