Computer Systems revisionApprox 25–35 min6 scenarios · justification practice
Recap: This section mixes every Computer Systems topic: translators, computer structure, text, graphics, numbers and security. Work out which topic each scenario is testing before you choose.
→ Full lesson: CS10 — Past Paper Practice
How to use this drill: Each scenario comes from a different part of the unit and has its own two choices. Justify each answer with a detail from the scenario, as you would in the exam. Reveal the model answer to check your reasoning.
Your choices and justifications are saved automatically.
Section E — Mixed CS
6 scenarios. Choose an answer, justify it using the scenario, then check the model answer.
Scenario 1 of 6Selling a finished app
A developer has finished a puzzle game and will sell it to customers. It must run quickly, and customers must not see the source code.
Expected: Compiler
A compiler. It translates the whole program once, before it runs, so the finished game runs without any translation overhead. Customers receive only the compiled program, so they never see the source code.
Scenario 2 of 6Reading a value
A value stored in memory is being copied into the processor.
Expected: Data bus
The data bus. The value itself travels along the data bus. The address bus is only used to say which location is being read.
Scenario 3 of 6Emoji in messages
A school's new messaging app must let pupils send emoji and write in their home languages.
Expected: UnicodeUnicode. With 16 bits per character it can represent 65,536+ characters, including emoji and the characters of other languages. Extended ASCII is limited to 256 characters.
Scenario 4 of 6Resizable diagram
A diagram of a bicycle made of lines and ellipses must be shown on a phone and also printed on an A2 poster.
Expected: Vector
A vector graphic. The diagram is made of objects (lines and ellipses) with attributes, so it can be redrawn at any size without becoming pixelated.
Scenario 5 of 6Shop prices
A shop's system stores prices such as £3.49 and £12.99 in binary.
Expected: Floating pointFloating point. The prices have a fractional part, so they are real numbers. Floating point stores them as a mantissa and an exponent.
Scenario 6 of 6Wi-Fi on a train
A passenger logs in to their bank on a train's public Wi-Fi. Anyone else on the train could capture the signals being sent.
Expected: EncryptionEncryption. Other passengers may capture the data, but if it is encrypted they cannot understand it without the key. A firewall would not stop the data being captured on the way.
Marker's eye view — why candidates lose marks
In mixed papers, the hardest part is working out which topic a question is testing. Underline the key words first — "sold to customers", "both directions", "emoji", "resized", "decimal", "intercepted" — then pick the topic.
Every justification should have two parts: a fact about your choice and a link to the scenario. A fact with no link, or a link with no fact, usually scores 1 mark out of 2.