← Revision N5 Computing Science  ·  James Gillespie's
CS  ·  Revision  ·  Section A

Translator or Compiler?
Decision Drill

Computer Systems revision Approx 30–40 min 8 scenarios  ·  justification practice
Recap: An interpreter translates and runs code line-by-line as the program executes; a compiler translates the whole program before it runs, producing object code or an executable.  → Full lesson: CS8 — Translators
How to use this drill: Read each scenario carefully — the clue words are in the detail. Select Interpreter or Compiler, then write a justification that uses evidence from the scenario. Do not just name a translator; connect it to what the scenario actually says. Reveal the model answer to check your reasoning.
Your choices and justifications are saved automatically.
Section A — Translator or Compiler?

Eight scenarios. Select a translator, justify your choice using the scenario, then check the model answer. Scenarios 5 and 8 are marked DISCUSS — either answer can be correct if well-justified.

Scenario 1 of 8 Finished game for distribution

A games studio has spent two years developing a 3D adventure game. The finished product will be sold on PC gaming platforms and downloaded by customers as an installer. The game must run smoothly at high frame rates, and customers should not have access to the source code.

Expected: Compiler A compiler is suitable. It translates the whole program before execution, so the finished game runs quickly without translation overhead on each launch — important for maintaining high frame rates. The game is distributed as an installer: customers receive only the compiled executable, not the original source code, protecting the studio's intellectual property.
Scenario 2 of 8 Learning Python while developing

A Higher Computing Science pupil is writing a sorting algorithm in Python for the first time. She has been adding a few lines at a time, running the program after each change, and checking immediately where errors appear so she can fix them before continuing.

Expected: Interpreter An interpreter is suitable. It translates and executes the code one instruction at a time as the program runs, so the pupil can test a few lines immediately after writing them without needing to compile the whole program first. Errors are reported as the code is executed, making it straightforward to locate and fix mistakes during active development.
Scenario 3 of 8 Medical device microcontroller

A company has finished writing embedded software for a pacemaker device. The software must respond to sensor readings within milliseconds. It must also fit within the device's very limited memory, and the company's algorithms must remain confidential — patients will never see the source code.

Expected: Compiler A compiler is required. Compiled code runs directly as machine code with no translation overhead, giving the fastest possible response time — critical when the software must react to sensor readings within milliseconds. The compiled executable is compact, better suited to the pacemaker's limited memory, and only the binary is installed in the device: the source code is never distributed to patients or third parties.
Scenario 4 of 8 Data analyst testing scripts

A business analyst is exploring a new sales dataset. He writes a short script to filter and group the data, runs it, checks the output, adjusts two or three lines, and runs it again. He repeats this cycle many times throughout the afternoon as he experiments with different approaches.

Expected: Interpreter An interpreter is suitable. The analyst is in a rapid test-and-adjust cycle — writing a short section, running it immediately, checking the result, and changing a few lines. An interpreter executes code without needing to compile the whole script first, giving instant feedback after each small adjustment. This suits a workflow based on frequent, small changes rather than producing a finished program.
Scenario 5 of 8 Beta-stage app with performance complaints Discuss

A startup team is midway through developing a new project management app. They are actively fixing bugs and releasing updated builds to 50 beta testers each week. Several testers have reported that the app feels sluggish when loading large projects.

Expected: Either — if justified using the scenario If choosing Interpreter: The team is still in active development, fixing bugs and pushing weekly updates. An interpreter supports rapid testing — bugs can be found and the code re-run immediately without recompiling between every fix.

If choosing Compiler: Beta testers have reported sluggish performance, which is a specific problem to solve. Compiled code runs without translation overhead, which could reduce loading times for large projects. Weekly release builds can be compiled each time.

Exam note: A weak answer says only "a compiler is faster" or "an interpreter is better for testing" without linking to the scenario. A strong answer connects the choice to the sluggishness complaint or the active bug-fixing cycle — whichever choice is made.
Scenario 6 of 8 Mobile app for the App Store

A developer has finished building a cycling navigation app for iPhone. She is submitting the finished app to the Apple App Store for distribution to thousands of users. The app must run efficiently on mobile hardware, and users will receive only the installed app — not the underlying code.

Expected: Compiler A compiler is suitable. The finished app is translated before distribution, producing an executable that runs efficiently on iPhone hardware without translation overhead on each launch. Distribution through the App Store means users receive only the compiled binary — the source code remains private to the developer.
Scenario 7 of 8 Live classroom demonstration

A teacher is introducing Python conditional loops to a class. He is typing short programs directly into the Python interactive shell on the projector, pressing Enter after each line to show pupils the immediate output. The programs are not being saved or distributed — this is a live demonstration only.

Expected: Interpreter An interpreter is in use. The interactive shell translates and executes each instruction as it is entered, producing immediate output after each line — this real-time feedback is what makes the live demonstration effective for teaching. There is no compiled program; the purpose is instruction-by-instruction execution with visible results shown instantly on the projector.
Scenario 8 of 8 Automation scripts with frequent updates Discuss

A freelance developer has written a set of daily automation scripts for a logistics company. The scripts process order data every morning and are considered complete — but the client expects to request small changes every few weeks as their processes evolve. The client has also asked that the scripts complete as quickly as possible to meet tight daily deadlines.

Expected: Either — if justified using the scenario If choosing Compiler: Speed is a stated requirement. Compiled code runs directly as machine code with no translation overhead, helping the scripts complete within the tight daily deadline. When the developer makes changes every few weeks, a new compiled version can be delivered to the client.

If choosing Interpreter: Small changes are expected every few weeks. With an interpreter, the developer edits the source code and the client runs the updated script immediately — no recompilation or redeployment step is needed, making changes quicker to apply.

Exam note: A strong answer links directly to either the speed requirement or the frequent-change expectation — not just a general statement about compilers being "faster" or interpreters being "easier to update." Both details are in the scenario; use whichever one you choose to defend.
Marker's eye view — why candidates lose marks

SQA course reports consistently identify the same pattern: candidates can define what a compiler and interpreter are, but lose marks when asked to recommend one for a scenario. The most common error is writing a general advantage — "a compiler is faster" — without connecting it to any detail in the question. A marker needs to see that you have read the scenario: "a compiler is suitable because the program needs to run quickly and be distributed to customers as an executable."

The second common error is vague language: "it is better," "it is more efficient," "it suits the situation." These phrases tell the marker nothing specific. Use precise vocabulary — translation overhead, executable, source code, line-by-line execution, testing phase — and attach each term to a clue word from the scenario.

For the two Discuss scenarios: there is no single correct answer, but there is a mark-winning approach. Name your choice, link it to one specific detail from the scenario, and do not waffle. A focused two-sentence justification scores better than a paragraph that tries to cover everything.