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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

An interpreter translates high-level code differently from a compiler.

Identify what an interpreter does immediately after translating a line of code.

[1 mark]
  • AExecutes the line
  • BProduces the object code
  • CSaves the line to a file
  • DTranslates the next line
Mark scheme
  • A Executes the line (1)
  • The only correct answer is A. The correct answer is that the interpreter executes the line.
  • B is not correct because an interpreter does not produce object code; that is what a compiler does
  • C is not correct because an interpreter does not save the translated code to a file
  • D is not correct because the interpreter executes the current line before it translates the next line
Example answers and how they were marked
Full marks1/1

A Executes the line

Why: Selected the line being executed straight after translation, which is how an interpreter works (1).

No marks0/1

D Translates the next line

Why: Near miss: the interpreter executes the translated line first and only then moves on to translate the next line, so no mark.

No marks0/1

B Produces the object code

Why: Confuses interpretation with compilation: object code is produced by a compiler, not an interpreter, so no mark.

2Describe2 marksTranslators Swap Remove

A high-level program must be translated into machine code before it can be run.

Describe how a compiler and an interpreter differ in when the translated code is executed.

[2 marks]
Mark scheme

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

  • The interpreter executes each line as soon as it has been translated (1) so translation and execution happen together/at the same time (1)
  • The compiler translates the whole program first (1) and the machine code is run later/separately (1)
  • The interpreter translates the code and runs it while the program is running (1) whereas the compiler does not run the code it produces (1)
  • The compiler produces translated code that is executed only after all the translation has finished (1) but the interpreter executes each line immediately (1)

Allow 'translates one line at a time' where it is linked to executing each line immediately.

Do not accept answers that only state that a compiler is faster/an interpreter is slower, without reference to when execution happens.

Do not accept answers that only give object code, error reporting or portability, without reference to when execution happens.

Do not accept the compiler executing the program as it translates it.

Example answers and how they were marked
Full marks2/2

The compiler translates the code first and the program is executed afterwards, but the interpreter executes each line as soon as it has been translated.

Why: Compiler translates the whole program first and it is executed afterwards (1) and interpreter executes each line as soon as it is translated (1).

Some marks1/2

The interpreter executes each line immediately after translating it.

Why: Correct interpreter timing (1); no comparison with when the compiler's translated code is executed.

No marks0/2

The compiler executes the program line by line as it translates it.

Why: Reverses the two translators; a compiler does not execute the program it translates, so no mark.

3Explain2 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.

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