GCSE Computer Science past papers, marked against the real criteria

AQA, Edexcel and OCR Computer Science papers with the mark scheme sitting beside every question. You write the answer in full — the trace table, the conversion working, the code — and it is marked the way an examiner marks it, point by point, including the steps that carry the marks when the final answer is already right.

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What "marked against the criteria" actually means

Computer Science is the subject where a pupil can see the answer in two seconds and still score almost nothing, because the question was not asking for the answer. A trace table is the clearest case.

The habit that cost four marks is answering what the algorithm does instead of executing it. It works every time on an algorithm you recognise, which is why nobody unlearns it, and it collapses on the one you do not — which is the one the paper is built to hand you.

The boards write in their own pseudocode

AQA and OCR each publish a reference language of their own, and the questions are written in it, so reading that notation is a skill the paper tests before you write a line of your own. Edexcel examines programming differently again: one of its papers is sat at a computer, writing and running real Python. Pupils who have only ever typed code, and never read an algorithm in someone else's notation, lose marks the moment they are asked what a given loop does.

Writing your answer in Python when the question showed pseudocode is usually fine: schemes generally accept any clear working approach, and small syntax slips that would not stop the code running are not normally penalised. What is not fine is losing the structure the question was marking. From the papers here: a three-mark question asks for a function that returns True or False. A solution with perfect logic that finishes with print(result) instead of a return drops the third mark, every time, because the mark is for returning a value and the code does not return one.

Worth knowing if you are a parent looking at the coursework: the practical programming every board requires does not contribute marks towards the grade. All of it is examined on the papers. Time spent building a project is not wasted, but it is not banked either.

Binary and hex: the answer is one mark, the working is the other

Conversion questions are worth one or two marks, and the two-mark version splits into a method mark and an answer mark. Take "convert the denary number 110 into 8-bit binary, showing your working". The method mark is for writing out the place values — 128, 64, 32, 16, 8, 4, 2, 1 — and picking 64 + 32 + 8 + 4 + 2, or for a correct repeated division by 2. The answer mark is for 01101110. A pupil who slips on the arithmetic but shows the place values still takes the method mark; a correct bare answer takes both, because it implies the method. The pupil who loses out is the one who guesses wrong in silence.

Two specific losses recur. The first is dropping the leading zero: 1101110 is seven bits and the question said eight, so the padding is part of the answer. The second is hexadecimal done digit by digit. Hex works in groups of four bits, because four bits give sixteen combinations and hex has sixteen symbols — so 01101110 splits into 0110 and 1110, which are 6 and 14, and 14 is E, giving 6E. Checking it backwards: 6 × 16 + 14 = 110. That grouping is the whole reason hex exists, and "how many bits does one hex digit represent" is a one-mark question precisely because it is the bit people skip.

State, describe, explain, and the point that only counts once

State and give want a word or a short phrase, and a paragraph earns no more than the phrase would. Describe wants what something is or what happens. Explain wants why, or what the effect is, and an answer that only describes scores nothing on an explain question however correct it is — "more cores" is an identification, "each core can execute instructions independently, so more instructions are processed at the same time" is the explanation, and the second mark lives in the word so.

Two counting rules cost real marks. Asked for two ways, the two must be different ideas: "do not click suspicious links" and "avoid clicking bad links" is one point written twice and scores once. And asked for two factors, writing four does not help — the extra lines are at best ignored, and the time went somewhere.

The last one is specific to this subject, and it separates a pupil who has learned the vocabulary from one who has understood it: a defence must match the threat. "Use a firewall" or "install antivirus" scores nothing as a way to prevent SQL injection, because neither one does. Parameterised queries and input validation do. Security questions are where a bank of half-remembered words looks most like an answer and marks least like one.

The papers

70 questions across 7 papers, each with its own criteria. Everything here is written in the boards' own format and judged against their published criteria; the papers themselves belong to the boards and are not reproduced here.

Try it on your own answer

Open a paper, write what you would have written in the exam, including the wrong bits, and read what comes back. It is free to start and does not ask for a card.

Open GCSE Computer Science

The other subjects

Twenty-three in one place, aligned to AQA, Edexcel and OCR.