Exam Tips (Cambridge (CIE) A Level Computer Science): Revision Note
Exam code: 9618
How the 9618 exams are structured
What papers do you sit?
Cambridge International AS & A Level Computer Science (9618) is assessed by up to four papers, each worth 75 marks
AS Level students sit Papers 1 and 2
A Level students sit all four papers, either all at once or staged over two years (Papers 1 and 2 first, then Papers 3 and 4)
Calculators are not allowed in any paper, so binary, hexadecimal and file size calculations must be done by hand
Paper | Duration | Weighting | What it involves |
|---|---|---|---|
Paper 1: Theory Fundamentals | 1 hour 30 minutes | 50% of AS, 25% of A Level | Written paper on syllabus sections 1 to 8; short and longer answers |
Paper 2: Fundamental Problem-solving and Programming Skills | 2 hours | 50% of AS, 25% of A Level | Written paper on sections 9 to 12; answers in pseudocode, with an Insert listing the built-in functions and operators |
Paper 3: Advanced Theory | 1 hour 30 minutes | 25% of A Level | Written paper on sections 13 to 20 |
Paper 4: Practical | 2 hours 30 minutes | 25% of A Level | Programming on a computer in Java, Visual Basic or Python (console mode), with no internet; code and test evidence go in an evidence document |
How long should you spend per mark?
Every paper is out of 75, so the time per mark depends on the paper's length
Papers 1 and 3: about 1 minute 10 seconds per mark
Paper 2: about 1 minute 35 seconds per mark
Paper 4: about 2 minutes per mark
A 6-mark algorithm question in Paper 2 is therefore worth about 10 minutes, so if you have spent 20 minutes on it, move on and come back later
What examiners are looking for
What are the assessment objectives?
Every mark in 9618 is awarded against one of three assessment objectives (AOs):
AO1: demonstrate knowledge and understanding of the principles and concepts of computer science
AO2: apply that knowledge and understanding, including to analyse problems in computational terms
AO3: design, program and evaluate computer systems to solve problems, making reasoned judgements about these
The balance changes between papers:
Papers 1 and 3 are 60% AO1 and 40% AO2, so nearly half of the marks need you to apply knowledge, not just recall it
Paper 2 is 40% AO2 and 60% AO3, so most marks come from designing and writing pseudocode
Paper 4 is 100% AO3, so every mark comes from working code and testing evidence
Across the full A Level, the split is AO1 30%, AO2 30% and AO3 40%: more marks come from programming and problem-solving than from recall
Top exam tips for 9618
Answer in the context of the scenario
Many questions are set around a scenario, such as a company, a school system or a device
Examiner reports note in almost every series that generic answers lose marks when the question gives a scenario
For example, if a question asks why lossy compression would not be used for a particular file, a description of lossy compression on its own scores nothing; the answer must say why it is unsuitable for that file
Use technical terms precisely
Computer science terms have exact meanings, and using the wrong one can change the meaning of the whole answer
Examiners give this example: compression does not make "the transmission speed faster"; it makes the time taken to transmit the file shorter, because transmission speed depends on the connection, not the file
Other distinctions examiners check include data vs information, memory vs storage, record vs file, identifier vs literal value, and
OUTPUTvsRETURNAvoid brand names: write "a word processor" rather than naming a product, as brand and company names cannot be credited
Match your answer to the command word
The command word tells you how much detail is needed
Identify or State needs a short, precise answer
Describe needs the features or steps
Explain needs the reason why or how, usually with a "because" or "so that"
Examiners point out that an "explain" question needs more detail than an "identify" question, so match the length and depth of your answer to the word
See the 9618 command words page for every word used in 9618 and how to answer each one
Do not repeat the question
Paper 2 examiner reports give this warning in most series: answering by repeating phrases from the question gains no marks
If the question says "a program stores scores in an array", writing "the program uses an array to store scores" adds nothing; each mark needs a new point
Read the whole question before you start
Some questions give an example in the stem and then exclude it from the answer
For example, if a question states that a range check is a validation check and asks for two other validation checks, a range check scores nothing
Look for words such as "other", "different", "apart from" and "using the given data"
Use Cambridge pseudocode, not your programming language
In Papers 2 and 3, pseudocode must follow the Cambridge Pseudocode Guide for Teachers
Python syntax such as
len(),+=orelifis not acceptable when a question asks for pseudocodeIn Paper 2, only use the functions listed in the Insert; examiners will not credit language-specific functions that are not in it
Do not use reserved words as identifiers:
DECLARE Input : STRINGandDECLARE Integer : INTEGERboth lost marks in recent series
Show your working and make the final answer clear
For number base conversions, floating-point questions and low-level program traces, write out your working
Some questions say "show your working" and award marks for it, so a correct answer alone may not get full credit
Underline or box your final answer so the examiner can find it
Attempt every question
Examiners report that even the hardest Paper 2 algorithm questions contain accessible marks, such as declaring variables, setting up a loop or returning a value
In Paper 4, students who skipped an earlier part could still gain marks on later parts, for example by calling a subroutine they had not managed to write
A blank answer is guaranteed to score zero
Worked Example
A photographer emails high-resolution photographs to a client. The client prints the photographs as large posters.
Explain why the photographer should not use lossy compression for these files.
[2]
Answer:
Weak answer (0 marks): "Lossy compression removes data from the file to make it smaller. It is used for images and sound."
This only describes lossy compression and never mentions the photographs or the posters.
Strong answer (2 marks):
Lossy compression permanently removes data from the file, so the original image cannot be restored [1 mark]
The posters are printed at a large size, so the lost detail would make them visibly lower in quality [1 mark]
The second mark is only available because the answer links the lost data to the client printing large posters.
Examiner Tips and Tricks
Before you write, underline the scenario details in the question; aim to use at least one of them in every answer that is worth more than 1 mark
When you finish a question, check that every point you have written is a new point, not the question reworded, because each mark needs a separate, creditworthy idea
Common mistakes that lose marks
These mistakes all appear in Cambridge examiner reports for 9618, most of them in more than one series
Mistake | Why it loses marks | Instead |
|---|---|---|
Describing a concept without linking it to the scenario | Application (AO2) marks need the scenario | Name the scenario in your answer and explain the effect on it |
| Without brackets, only |
|
|
| Use |
| The value never reaches the calling code | Use |
Using | The question asked for values to be passed in | Use the parameters given in the subroutine header |
Writing in pencil and then going over it in ink | Scanned scripts pick up both, and illegible answers score nothing | Plan on a blank page and cross the plan out |
Squeezing a corrected answer into the original space | The examiner may not be able to read it | Write it on a blank page and add a note such as "see additional page 1" |
Giving more answers than the question asks for | Only the first answers up to the number asked for are marked, and only the first answer in each numbered space | Give exactly the number asked for, one per numbered space |
Paper 4: how do you lose marks on evidence?
In Paper 4, marks can only be given for what is in the evidence document
Examiner reports highlight these problems:
Code pasted as a screenshot instead of copied as text, which can be unreadable (especially on a dark integrated development environment (IDE) background)
Code cut off at the edge of the page, or the start of a subroutine missing
Test screenshots that do not show the input data, so the examiner cannot check that the output matches it
Paste code as text, check that every line is visible, and make sure each test screenshot shows both the input and the output
How to revise for each paper
Each paper needs a different kind of practice:
Paper 1: learn definitions precisely, then practise applying them to unfamiliar scenarios
Paper 2: write pseudocode by hand under timed conditions, using the Insert
Paper 3: practise the multi-step methods (floating-point normalisation, Boolean algebra, Karnaugh maps, Dijkstra's algorithm) until each step is automatic
Paper 4: write and test full programs on a computer in your chosen language, and practise filling in an evidence document
See the guide for each paper for its question types, plus the command words and pseudocode pages:
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