Data Representation is a core part of GCSE Computer Science. Revise the key concepts and common mistakes below, then lock them in with the free games.
Key concepts
BinaryBase-2 representation using only 0s and 1s.
HexadecimalBase-16, a shorthand for binary (0–9, A–F).
Bits & bytesA bit is one binary digit; 8 bits make a byte.
Character encodingASCII and Unicode represent text as binary codes.
Image representationImages stored as pixels with a colour depth.
Sound representationSound sampled at a rate and bit depth to store digitally.
Logic gatesAND, OR and NOT process binary inputs.
Truth tablesShow every output for all input combinations.
Boolean algebraRules for manipulating logic expressions.
AND gateOutput is true only when all inputs are true.
OR gateOutput is true when at least one input is true.
NOT gateInverts a single input (1→0, 0→1).
ExpressionA combination of variables and Boolean ops.
PrecedenceOrder: NOT first, then AND, then OR.
Common mistakes to avoid
Questions where students often pick the tempting wrong answer — make sure you know the right one:
What is the denary value of binary 10110?✗ 10110 (treating it as a denary number). ✓ 22 (16 + 4 + 2).
What happens when 11111111 + 1 is computed in an 8-bit register?✗ It just becomes 100000000 normally. ✓ Overflow - the result requires 9 bits but only 8 are available.
How do computers store all data?✗ In ordinary decimal numbers. ✓ As binary — 0s and 1s.
What affects the file size of an image?✗ Only the size of the screen showing it. ✓ Resolution (number of pixels) and colour depth.
Does the binary number 10 mean ten?✗ Yes - 10 is ten no matter what base it is written in. ✓ No - in binary, 10 means one two and zero units, which is the denary value two; the same symbols mean different values in different bases.
Practise Data Representation — free games
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