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Edexcel GCSE Computer Science (1CP2) Exam Questions

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3 questions · 5 marks

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1Multiple choice1 markTranslators Swap Remove

A compiler translates source code into machine code.

Identify why a compiled program can be run on a computer that does not have the compiler installed.

[1 mark]
  • AThe code is translated again each time it is run
  • BThe code is translated one line at a time
  • CThe object code is saved as a separate file
  • DThe source code is saved with the program
Mark scheme
  • C The object code is saved as a separate file (1)
  • The only correct answer is C. The correct answer is the object code is saved as a separate file.
  • A is not correct because a compiled program is not translated again when it is run
  • B is not correct because translating one line at a time is how an interpreter works
  • D is not correct because the source code is not needed to run a compiled program
Example answers and how they were marked
Full marks1/1

C The object code is saved as a separate file

Why: Selected the saved object code, which can be run without the compiler being present (1).

No marks0/1

D The source code is saved with the program

Why: Near miss: it is the object code, not the source code, that is saved and run on another computer.

No marks0/1

B The code is translated one line at a time

Why: Confuses a compiler with an interpreter: a compiled program is translated as a whole and is not translated again when it is run.

2Describe2 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.

3Explain2 marksTranslators Swap Remove

A program can be translated by a compiler or by an interpreter.

Explain why a compiled program usually runs faster than an interpreted program.

[2 marks]
Mark scheme

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

  • The compiler translates the whole program into machine code before it is run (1) so no translation is needed while the program is executing (1)
  • The machine code/object code is already produced before execution (1) so the CPU can carry out the instructions directly without translating them (1)
  • The compiled program does not need an interpreter at run time (1) so no time is spent translating each line before it is executed (1)

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

A statement that translation happens before execution, with no linked reason for faster running, earns 1 mark only.

Do not accept 'faster to run' or 'quicker' on its own without a reason linked to translation before/during execution.

Do not accept 'compiled code is optimised' or 'compilation takes less time' without linking this to translation before execution/at run time.

Do not accept answers about the compiler being installed or available.

The question asks why a compiled program usually runs faster, so answers must refer to when translation happens, not just general performance claims.

Example answers and how they were marked
Full marks2/2

The compiler translates the whole program into machine code before it is run, so the CPU does not have to translate each line during execution.

Why: Translation before execution (1) linked to no translation needed during the run, so faster (1).

Some marks1/2

The compiler translates the whole program first.

Why: Pre-translation point (1) but no link to faster running.

No marks0/2

A compiled program runs faster because the compiler is installed on the computer.

Why: Compiler being installed does not make execution faster; no credit.

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