Practise 110 real questions on Data representation from 2021 to 2026. See the answer and explanation as soon as you answer.
Data representation is one of the 10 main topics in our A Level Computer Science (Cambridge (CAIE) 9618) question bank, and about 10% of its real questions come from it. Tayyari Karo has 110 real questions on this topic from 2021 to 2026, from Paper 1, Paper 2, Paper 3. By difficulty: 43 easy, 38 medium, 29 hard.
Work through the questions below, then open the explanation for each one. Redo the ones you missed a few days later.
These are real past-paper questions. Think of your answer first, then open the explanation.
Identify one other character set and explain how it is different from UNICODE. [3]
1 mark for the identification: ASCII (accept extended ASCII or any other valid character set). Up to 2 marks for differences: fewer bits per character (ASCII 7/8 bits, UNICODE many more); fewer different characters can be represented (ASCII only the Latin alphabet); ASCII cannot be expanded indefinitely.
ASCII uses 7 or 8 bits and represents far fewer characters than UNICODE.
(b)(ii) The Unicode character '❮' has the binary value: 0010 0111 0110 1110. Convert the binary value for the character '❮' into denary.
10,094
1 mark.
Calculate the normalised binary floating-point representation of -76.1875 in this system. Show your working.
Working: 76.1875 = 64+8+4+0.125+0.0625 = 1001100.0011
-76.1875 = -128+32+16+2+1+0.5+0.25+0.0625 = 10110011.1101
Normalised: 1.01100111101 × 2^7
Mantissa: 101100111101
Exponent: 0111
Four marks for working and correct answer.
(c) Subtract the denary number 23 from the two's complement binary number 01001010. Perform this calculation using binary subtraction. Show your working.
Working:
23 in binary = 00010111 so minus 23 is 11101001
01001010 + 11101001 = (1)00110011
Direct subtraction:
01001010 - 00010111 = 00110011
Answer: 00110011
2 marks: 1 for working, 1 for answer.
(d)(vi) Show the result of a 3-place right logical shift on the binary number: 11001100
00011001
1 mark.
(b) Perform the following binary subtraction. Show your working.
10110011 − 01110101
00111110
Working using borrowing:
1 10 10 1
1 0 1 1 0 0 1 1
0 1 1 1 0 1 0 1
−
0 0 1 1 1 1 1 0
Working using two's complement:
10110011
Two's complement of 01110101 = 10001011
10110011
+ 10001011
=(1)00111110
2 marks: 1 for working, 1 for answer.
(b)(ii) Evaluate your infix expression from part (b)(i) when a = 5, b = 10, c = 27 and d = 12.
–39
1 mark.
(d)(ii) Explain how the computer system could be modified to store the denary number 513.
• The number of bits for the mantissa must be increased
• 11/12 bits mantissa and 5/4 bits exponent
2 marks: one mark for each correct marking point.
| Session | Paper 1 | Paper 2 | Paper 3 |
|---|---|---|---|
| May/June 2026 | 8 | – | 4 |
| May/June 2025 | 6 | – | 2 |
| October/November 2025 | 8 | – | 2 |
| May/June 2024 | 4 | – | 2 |
| October/November 2024 | 8 | – | 2 |
| May/June 2023 | 11 | – | 3 |
| October/November 2023 | 3 | – | 5 |
| May/June 2022 | 4 | – | – |
| October/November 2022 | 8 | – | 7 |
| May/June 2021 | 6 | – | 5 |
| October/November 2021 | 8 | 1 | 3 |
110 real A Level Computer Science (9618) questions on Data representation from 2021 to 2026, from Paper 1, Paper 2, Paper 3. Each one shows the year, session and paper it came from.
Yes. Every question shows the correct answer and a short explanation the moment you answer.
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