Languages, translators and IDEs – GCSE Computer Science exam questions with mark scheme

1Grade 1–32 marks

Give two characteristics of a high-level language. [2]

Any one from: uses English-like keywords / statements; easier for humans to read / write / understand / debug / maintain (than low-level code); one statement translates into many machine-code instructions; portable / not tied to one type of processor (hardware-independent); must be translated (by a compiler or interpreter) before the CPU can run it; programmer does not need to manage memory / registers directly. Reject 'easy' or 'simple' with no qualification. Easier to read and easier to write count as one point(1)
A second, different characteristic from the list(1)
Answer: e.g. English-like; portable across processors
Examiner tip: 'Easy' on its own is too vague. Say it is easy to read or write because it uses English-like words.

2Grade 4–54 marks

Describe two differences between a compiler and an interpreter. [4]

First difference – compiler side, e.g. translates the whole program in one go / produces an executable (object code) file that runs without the compiler or source code / reports all errors after translating the whole program / compiled program runs faster as it is already translated(1)
…matching interpreter side of the same difference, e.g. translates and runs one line (statement) at a time / produces no executable, so the interpreter (and source code) is needed every time the program runs / stops at the first error it finds, so errors are easier to locate / runs more slowly as each line is translated every time it runs(1)
Second, different difference – compiler side (from the list above)(1)
…matching interpreter side of the second difference. Each side may be credited on its own if correct, but the same difference cannot be credited twice(1)
Answer: e.g. Compiler translates the whole program at once, whereas an interpreter translates and runs one line at a time. Compiler produces an executable file, whereas an interpreter produces no executable, so it is needed every time the program runs.
Examiner tip: Each difference needs both sides (compiler … whereas interpreter …) to get both marks.

3Grade 4–53 marks

(a) Give one example of a low-level language. [1]

(b) Explain why a programmer might choose to write a program in a low-level language. [2]

(a) Assembly language / machine code; allow a named assembly language (e.g. LMC, ARM / x86 assembly). Reject 'binary' alone(1)
(b) Any two from: gives direct control of the hardware / memory / registers / specific processor features; program runs faster / more efficiently (fewer instructions, so it executes quickly); program uses less memory / is smaller; suitable where resources are limited or hardware-specific code is needed, e.g. embedded systems, device drivers; allow: no (or minimal) translation needed / machine code runs directly on the CPU(1)
(b) Second, different reason from the list (an expansion of the first point, e.g. direct control so the code runs faster, also earns this mark)(1)
Answer: (a) Assembly language; (b) direct hardware control, so the code can be faster and more memory-efficient
Examiner tip: An 'explain' question needs a reason plus its effect, e.g. direct control of the hardware, so the code runs faster.

4Grade 4–54 marks

Describe two features of an IDE that help a programmer find and fix errors. [4]

Feature 1 identified, from: error diagnostics / error messages; breakpoints; stepping (step through line by line); variable watch / trace; run-time environment; debugger / debugging tools (if the description says what it does, e.g. step through, breakpoints, watch values); allow translator if linked to reporting (syntax) errors; allow syntax highlighting or line numbers if linked to spotting / locating errors. Do not award auto-complete / auto-indent / code completion (these help avoid errors rather than find them)(1)
Feature 1 described, e.g. error diagnostics highlight the line containing an error and explain what is wrong; breakpoints pause the program at a chosen line; stepping runs one line at a time; watch shows variable values as the program runs; run-time environment lets the program be run and tested inside the IDE so run-time errors and output can be seen; syntax highlighting colours keywords so mistyped keywords stand out; line numbers let the programmer go straight to the line named in an error message; translator reports syntax errors (with line numbers) when the code is translated(1)
Feature 2 identified (different from feature 1)(1)
Feature 2 described(1)
Answer: e.g. error diagnostics (highlight and explain errors); breakpoints (pause to inspect variables)
Examiner tip: Pick tools that help find errors, such as error diagnostics or breakpoints, and say what each one does; auto-complete or auto-indent help you avoid errors rather than find them, so choose a debugging tool instead.

5Grade 6–74 marks

A games company is about to sell a new game to customers.

Explain whether the company should give customers a compiled version of the game or the source code to be interpreted. [4]

Recommends the compiled version (only award if at least one valid reason is given; no marks for recommending source code)(1)
Customers do not need a translator (compiler / interpreter) installed to run the game; allow: customers just run the executable file(1)
The source code is not given out, so it cannot easily be copied, stolen or changed (protects the company's intellectual property / stops cheating by editing the code)(1)
The compiled game runs faster because it is already translated (no translation while it runs); allow: errors have already been found during compilation(1)
Answer: Compiled: no translator needed, source code is protected, and it runs faster.
Examiner tip: Link each point to this scenario, i.e. customers and protecting the game's code. Generic compiler facts score less.

6Grade 4–53 marks

(a) Explain why programs written in a high-level language need to be translated. [2]

(b) Give one reason why a programmer might use an interpreter rather than a compiler while they are still writing and testing a program. [1]

(a) The CPU / processor can only execute machine code / binary(1)
(a) …so the high-level source code must be converted into machine code before (or while) it runs(1)
(b) Any one from: it stops at the line where an error occurs, so errors are easier to find; the program can be run / tested without translating the whole program first (quicker to test small changes); can run code that still contains errors in later lines(1)
Answer: (a) The CPU only understands machine code, so the high-level code must be turned into machine code. (b) e.g. it stops at the line with the error, making debugging easier.
Examiner tip: In (a) say what the CPU can run (machine code), not just that it 'can't understand' the program.

Still losing marks on this topic?

Book a free introductory session and we'll find exactly which step is costing you.

Book a free intro