Lesson 3 - Exam practice
Test your knowledge
Work through these questions as you would in an exam. Answer the MCQ first, then write your answers to the written questions before revealing the mark scheme.
Section 1: Multiple choice
Select one answer per question. Instant feedback appears when you choose.
Question 1 of 5
How many characters can standard 7-bit ASCII represent?
Standard ASCII uses 7 bits, giving 2&sup7; = 128 possible characters (codes 0-127). Extended ASCII uses 8 bits for 256 characters.
Question 2 of 5
The ASCII code for 'A' is 65. What is the ASCII code for 'D'?
ASCII letters are sequential. D is the 4th letter: A=65, B=66, C=67, D=68.
Question 3 of 5
Which encoding standard supports over 140,000 characters from most of the world's writing systems?
Unicode is the global standard. UTF-8 is one encoding form of Unicode, but Unicode itself is the character set that defines over 140,000 code points.
Question 4 of 5
A plain text file contains 500 characters stored as ASCII (1 byte each). What is the file size in bits?
500 characters × 1 byte × 8 bits = 4,000 bits. Always multiply bytes by 8 to get bits.
Question 5 of 5
Why does UTF-8 use a variable number of bytes per character?
UTF-8 uses 1 byte for standard ASCII characters (codes 0-127) and 2-4 bytes for additional Unicode characters. This makes it backward-compatible with ASCII while supporting all Unicode code points.
Section 2: Written questions
Write a full answer in your notebook or on paper before checking against the lesson notes.
Written question 1
The word 'Key' is stored using ASCII. Give the 8-bit binary for each character. (K=75, e=101, y=121)
3 marks
Written question 2
Explain why Unicode was developed to replace ASCII, giving two specific limitations of ASCII that it overcomes.
4 marks
Written question 3
A student argues that UTF-8 always uses more memory than ASCII. Evaluate this claim.
5 marks