About Data representation in O Level Computer Science
Data representation is one of the 4 main topics in our O Level Computer Science (Cambridge (CAIE) 2210) question bank, and about 12% of its real questions come from it. Tayyari Karo has 23 real questions on this topic from 2021 to 2026, from Paper 1. By difficulty: 15 medium, 8 easy.
Work through the questions below, then open the explanation for each one. Redo the ones you missed a few days later.
Try 4 real questions
These are real past-paper questions. Think of your answer first, then open the explanation.
Oct/Nov 2024 · Paper 1 · Data representation
1 (a) Tick one box to show which of these is not a unit of measurement for a file: bit, bot, nibble, byte.
(b)(i) Give two types of compression that can be used to reduce the size of a file. (ii) Give three benefits of reducing the size of a file for storage and transmission.
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1 (a) bot. (b)(i) Lossless compression and lossy compression. (ii) Three benefits: uses less storage space; faster to transmit / upload / download; lower bandwidth / transmission cost; more files fit on the storage medium. (Any three.)
Oct/Nov 2023 · Paper 1 · Data representation
5 A musician records piano music.
(a) Explain how the analogue sound is recorded and converted to digital.
(b) State two ways the accuracy of the recording could be increased.
(c) The musician uses lossless compression instead of lossy compression. Explain why.
(d) Explain the differences between the ASCII and Unicode character sets.
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5 (a) A microphone converts sound waves into an analogue electrical signal; an analogue-to-digital converter (ADC) samples the signal at regular intervals and quantises each sample to a binary value, producing a digital file.
(b) Increase the sampling rate (more samples per second); increase the bit depth/resolution (more bits per sample).
(c) Lossless compression does not lose any data, so the original recording can be reconstructed exactly with no loss of quality, which matters for music.
(d) ASCII uses 7 (or 8) bits and represents 128 (or 256) characters, mainly for English; Unicode uses more bits (e.g. 16) and can represent characters/symbols from many world languages. …
The full model answer is in the app.
May/June 2022 · Paper 1 · Data representation
All data needs to be converted to binary data so that it can be processed by a computer. (a) Explain why a computer can only process binary data. (b) The denary values 64, 101 and 242 are converted to 8-bit binary values. Give the 8-bit binary value for each denary value. (c) The hexadecimal values 42 and CE are converted to binary. Give the binary value for each hexadecimal value.
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(a) Computer circuits have two states (on/off, high/low voltage) which are naturally represented by the two binary digits 0 and 1; this makes processing reliable and simple.
(b) 64 = 01000000; 101 = 01100101; 242 = 11110010.
(c) 42 (hex) = 01000010; CE (hex) = 11001110.
64=01000000, 101=01100101, 242=11110010; 42h=01000010, CEh=11001110.
Oct/Nov 2021 · Paper 1 · Data representation
1 (a) Tick one box to show whether binary is a base-2, base-10 or base-16 number system.
(b) Hexadecimal and denary are number systems that can be used by programmers. Convert these four hexadecimal values into denary values: 09, 10, 28, A1.
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1 (a) Base-2.
(b) 09 = 9, 10 = 16, 28 = 40, A1 = 161.
