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Edexcel GCSE Computer Science (1CP2) Exam Questions

Build a practice paper from 659 exam-style questions, each with its mark scheme and example answers. Print it, or answer it on paper and then open the mark schemes. Or browse the questions by topic.

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3 questions · 6 marks

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1Describe2 marksTranslators Swap Remove

Source code can contain syntax errors.

Describe how a compiler and an interpreter differ in the way they deal with syntax errors.

[2 marks]
Mark scheme

Award up to two marks for a linked description such as:

  • The compiler reports all syntax errors after translation has finished (1) whereas the interpreter stops at the first error it finds (1)
  • The interpreter reports a syntax error as soon as it finds one (1) and does not translate/execute any more of the program (1)
  • The compiler continues translating after an error (1) and reports the errors at the end (1)
  • The interpreter stops translating when it reaches an error (1) but the compiler finishes translating before reporting errors (1)

Do not accept answers about fixing/correcting errors or about object code.

Do not award 'the compiler finds more errors' without saying errors are reported at the end.

Example answers and how they were marked
Full marks2/2

A compiler reports all the syntax errors at the end of translation, whereas an interpreter stops and reports the error as soon as it finds one.

Why: Compiler reports errors at the end (1) and interpreter stops/reports at the first error (1).

Some marks1/2

An interpreter stops translating when it finds a syntax error.

Why: Interpreter stops at the first error (1); no comparison with when the compiler reports errors.

No marks0/2

A compiler reports a syntax error immediately, before translating the rest of the program.

Why: Reverses the compiler's behaviour; it finishes translating before reporting errors.

2Explain2 marksTranslators Swap Remove

A programmer writes a program in a high-level language. The program is translated by a compiler.

Explain why a compiler must translate the whole program before any of it can be executed.

[2 marks]
Mark scheme

Award up to two marks for a linked explanation such as:

  • The compiler produces object code/machine code for the whole program (1) so there is no complete executable until every line has been translated (1)
  • The compiler translates all the source code before producing the object code (1) so the program cannot start until translation has finished (1)
  • The compiler checks the whole program for errors during translation (1) so all of the source code must be read before an executable can be produced (1)

For both marks, the expansion must follow/associate with the statement.

Allow 'in one go'/'all at once' for the translation point, but this does not earn the second mark unless it is linked to why the program cannot be executed until translation has finished.

A statement that the whole program is translated, with no linked reason about when the program can be executed, earns 1 mark only.

Do not accept 'a compiler is faster' or 'compiled code runs faster' on its own; this does not explain why translation must finish before execution.

Do not accept 'it translates and runs the program one line at a time', as this describes an interpreter.

Example answers and how they were marked
Full marks2/2

A compiler produces object code for the whole program, so there is no complete executable until every line has been translated.

Why: Object code for the whole program (1) linked to there being no complete executable until every line is translated (1).

Some marks1/2

A compiler translates the whole program in one go.

Why: Translation of the whole program only (1); no linked reason about when the program can be executed, so the second mark is not awarded.

No marks0/2

A compiler translates and runs the program one line at a time, so it stops when it finds an error.

Why: Confuses a compiler with an interpreter; nothing about translating the whole program before execution, so no creditworthy point.

3Explain2 marksLow and High Level Languages Swap Remove

A programmer writes the same program in a low-level language and in a high-level language.

Explain one reason why the program written in the low-level language may run faster.

[2 marks]
Mark scheme

Award up to two marks for a linked explanation such as:

  • The programmer can choose the most efficient instructions/registers to use (1) so the program completes its task in fewer steps (1)
  • The programmer can optimise the code for the processor (1) because low-level instructions give direct control of registers/memory (1)
  • Each low-level instruction maps to one machine code instruction (1) so fewer instructions are executed than for the equivalent high-level code (1)
  • The translated code is smaller (1) so fewer instructions are fetched from memory and executed (1)

For both marks, the expansion must follow/associate with the statement.

Do not accept 'it is low-level' / 'it is closer to machine code' / 'low-level code is faster' on its own without a reason why it makes the program run faster.

Do not accept 'high-level code has to be translated' / 'high-level code is interpreted' on its own without saying why that makes the program slower.

Do not accept 'the code is smaller' on its own without saying that this means fewer instructions are fetched/executed.

Do not accept 'it is easier to write' or 'quicker to type' as a reason for faster execution.

Example answers and how they were marked
Full marks2/2

The programmer can choose the most efficient instructions and registers to use so the program completes its task in fewer steps.

Why: Linked point (1) of choosing efficient instructions/registers and reason (1) that the task is completed in fewer steps, so it runs faster.

Some marks1/2

Each low-level instruction maps to one machine code instruction so the program is shorter to type.

Why: Point (1) that one low-level instruction maps to one machine code instruction, but being shorter to type does not explain why the program runs faster, so no second mark.

No marks0/2

Because it is closer to machine code.

Why: 'Closer to machine code' alone gives no reason why that makes the program run faster, and the mark scheme does not accept it on its own.

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5.3 Cybersecurity

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