Paper 1 — Theory of Computer Systems
What is Paper 1 actually testing?
Think of Paper 1 as the "under the hood" paper. It's not really asking you to
anything with a computer — it's asking whether you understand
how a computer system is built and how it functions, from the way a single
character gets turned into binary, all the way up to how your phone talks to a
web server on the other side of the world. It's a knowledge-and-understanding-heavy
paper, though it still expects you to apply that knowledge to real-life ICT contexts
rather than just recite facts.
Paper 1 — Key Facts
Duration: 1 hour 45 minutes | Marks: 75 |
Weighting: 50% of the IGCSE | Calculator: Not permitted |
Grade range covered: A* to G
The six topics Paper 1 covers
Every question on Paper 1 is drawn from Topics 1 through 6 of the syllabus, and — importantly — each question is dropped into its own real-world ICT scenario, rather than being asked abstractly.
Topic 1Data Representation
Topic 2Data Transmission
Topic 3Hardware
Topic 4Software
Topic 5The Internet and its Uses
Topic 6Automated and Emerging Technologies
How the paper is structured
It's a written paper made up of short-answer and structured questions —
meaning you'll see a mix of one-line factual answers and longer, multi-part questions
that build on each other. You answer directly on the question paper (there's no
separate answer booklet), and critically, every question is compulsory — there's
no "answer 3 out of 5" choice like you might get in some other subjects. That means you
genuinely need to revise the whole syllabus, not just your favourite topics.
The three Assessment Objectives (AOs)
Every mark on Paper 1 (and Paper 2) is assigned to one of three AOs. Understanding these
is one of the most underrated revision tricks — it tells you
a question wants before you even fully read it.
| AO | What it means | What this looks like in a question |
|---|
| AO1 | Demonstrate knowledge and understanding of principles and concepts | "State", "Define", "Identify" — recall a fact or definition |
| AO2 | Apply knowledge and understanding to analyse problems | "Calculate", "Explain why", "Describe how" — use the fact in a given scenario |
| AO3 | Provide solutions by evaluating, making judgments, and presenting conclusions | "Compare", "Evaluate", "Justify your answer" — weigh options and conclude |
Why this matters
If a question says "Define," and you write three sentences with an example and an evaluation,
you're not getting extra marks — you're just running out of time. Match your answer
and to the AO the command word signals.
The maths skills Paper 1 assumes you have
Because there's no calculator, and because data representation is a whole topic, you're
expected to be comfortable — — with:
- Basic arithmetic (add, subtract, multiply, divide)
- Boolean operators (AND, OR, NOT — these come back hard in Topic 10 on Paper 2, but the logic starts here)
- Converting between binary, denary (normal decimal), and hexadecimal number systems
- Counting, totalling, and rounding — the unglamorous skills that quietly cost marks if you're rusty
Practice Question 1
Q: How many topics does Paper 1 cover, and roughly what do they have in common as a group?
Practice Question 2
Q: A question on Paper 1 says "Explain why fibre-optic cable is used instead of copper cable for a long-distance connection." Which AO is this mainly testing, and what does that tell you about how to answer it?
Paper 2 — Algorithms, Programming and Logic
What is Paper 2 actually testing?
If Paper 1 is "how does a computer work," Paper 2 is "can you think like a programmer."
This paper cares less about facts and more about your ability to break a problem down,
design a solution, and express that solution as a clear, logical sequence of steps — whether
that's an algorithm, a flowchart, a database query, or a logic circuit.
Paper 2 — Key Facts
Duration: 1 hour 45 minutes | Marks: 75 |
Weighting: 50% of the IGCSE | Calculator: Not permitted
The four topics Paper 2 covers
Topic 7Algorithm Design and Problem-Solving
Topic 8Programming
Topic 9Databases
Topic 10Boolean Logic
Same skeleton as Paper 1, same three AOs
Structurally, Paper 2 is a mirror of Paper 1: a written paper of short-answer and structured
questions, all compulsory, answered directly on the paper, no calculator, and marked against the
same AO1 / AO2 / AO3 framework — except here, AO2 and AO3 tend to show up as "design/write this
algorithm" and "evaluate this program/solution" rather than "explain this hardware choice."
| AO | What it means on Paper 2 |
|---|
| AO1 | Knowledge and understanding of computer science principles and concepts |
| AO2 | Applying knowledge to a given context — including computational or programming problems |
| AO3 | Providing solutions by computer systems, making reasoned judgments, and presenting conclusions |
The big one: the final scenario question
This is the single most distinctive feature of Paper 2, and it's worth building your whole
revision strategy around it. The last question on Paper 2 is an unseen scenario worth 15 marks
— nearly a fifth of the entire paper's marks in one question. You'll be given a brand-new
real-world context you haven't seen before, and asked to write a complete algorithm using
either pseudocode or actual program code to solve it.
Time management tip
You're expected to spend 30 minutes on this one question alone — that's nearly a third
of your total exam time. If you're still deep in earlier questions with 30 minutes left on the
clock, that's your cue to move on and come back if there's time. Practising past-paper scenario
questions is one of the highest-value things you can do
before the real exam.
You don't need to memorise exact syntax
This is genuinely good news, and a lot of students don't realise it until too late. The syllabus
explicitly says knowledge of programming language syntax is not examined — what's being
tested is your . When you write pseudocode, you're not expected to reproduce the exact
syntax shown in the syllabus guide word-for-word — your answer just needs to be clear enough that
a competent programmer could read it and understand exactly what you mean.
That said, there's still a "house style" worth following so your pseudocode reads cleanly:
- Keywords in UPPERCASE — e.g.
IF, REPEAT, PROCEDURE
- Identifiers (variable/procedure names) in mixed case — e.g.
NumberOfPlayers
Example of the expected pseudocode "house style":
PROCEDURE CheckScore(NumberOfPlayers)
IF NumberOfPlayers > 10 THEN
OUTPUT "Too many players"
ELSE
REPEAT
OUTPUT "Enter score"
UNTIL NumberOfPlayers = 0
ENDIF
ENDPROCEDURE
Flowcharts and logic gates: symbols are not optional
Unlike pseudocode syntax, where you have flexibility, flowchart symbols and logic gate
symbols are standardised and you're expected to use the exact ones from the syllabus —
an oval for start/end, a rectangle for a process, a diamond for a decision, and the correct
AND/OR/NOT/NAND/NOR/XOR gate shapes for logic circuits. Drawing your own "creative" version
of a decision box can cost you marks even if your logic is correct, because the examiner is
also checking that you know the standard conventions.
Note
This is the flip side of the "syntax doesn't matter" rule above — that rule applies to
, not to . Flowcharts and logic gates have one
correct symbol set, and it's worth drilling until it's automatic.
The maths skills Paper 2 assumes you have
Paper 2 draws on a slightly wider set of maths skills than Paper 1, because algorithms often involve real calculations:
- Add, subtract, multiply, divide
- Averages, random numbers, decimals, fractions, percentages, and ratios
- Both positive and negative integers, and real numbers
- Arithmetic and Boolean operators
- Binary, denary, and hexadecimal number systems
- Counting, totalling, and rounding
Standard algorithms you're expected to know cold
Two searching algorithms and two sorting algorithms come up repeatedly across past papers,
and you're expected to be able to trace through them step-by-step, not just name them:
| Type | Algorithm |
|---|
| Searching | Linear search, Binary search |
| Sorting | Bubble sort, Insertion sort |
Practice Question 1
Q: You're told your Paper 2 pseudocode answer doesn't exactly match the syntax in the official syllabus guide. Does that mean you'll lose marks? Why or why not?
Practice Question 2
Q: The final question on Paper 2 is worth 15 marks and involves a context you've never seen before. How should you time your exam to account for this, and what form can your answer take?
Exam Tips — Traps and What Examiners Look For
Common Mistake #1
Writing an AO1-style one-word answer to an AO3 command word like "Evaluate" or "Justify."
These questions want you to weigh up more than one point of view and reach a conclusion —
a single sentence rarely earns full marks here.
Common Mistake #2
Panicking about "getting the pseudocode syntax exactly right." You don't need to. Focus your
revision time on getting the correct — the sequencing, the conditions, the loop
boundaries — rather than memorising the syllabus's exact pseudocode reference sheet word for word.
Common Mistake #3
Running out of time on Paper 2 because the final 15-mark scenario question was left too late.
Since it's worth 20% of the paper's marks and needs real thinking time, practise finishing your
earlier questions with at least 30 minutes left on the clock.
Common Mistake #4
Freehand, "creative" flowchart or logic gate symbols. Examiners mark against the standard
symbol set — a wonky home-made symbol for a decision box can lose you a mark even when your
underlying logic is perfect.
What examiners actually look for
- Command words matched correctly to the length and depth of your answer
- Working shown for any number-system conversions or calculations, not just a final answer
- Pseudocode/algorithms that a stranger could follow line-by-line without guessing your intent
- Answers placed in the specific real-world context given, not generic textbook definitions