Edexcel GCSE Computer Science (1CP2) Exam Questions

• A Decodes instructions (1)
• The only correct answer is A. The correct answer is Decodes instructions.
• B is not correct because the arithmetic logic unit performs arithmetic operations
• C is not correct because main memory stores data and instructions
• D is not correct because registers temporarily store data being processed

Award one mark for each of:

• 5 × 1024^3 / 5 × 1024 × 1024 × 1024 / 5 × 2^30, for the number of bytes (1)
• A fully correct expression with × 8 to convert bytes to bits, in any order, e.g. 5 × 1024^3 × 8, 8 × 5 × 2^30 (1)

Accept 5 × 1 073 741 824 × 8.

Accept 5 × 2^33 or 42 949 672 960 as a fully correct expression (2 marks).

Do not accept 5 × 1000^3 × 8, which uses decimal multiples.

Do not accept ÷ 8, which converts bits to bytes.

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

• A compiler produces object code/machine code/an executable (file) (1) whereas an interpreter produces no object code/translated file (1)
• A compiler produces a machine code file (1) that can be run on its own/without the compiler/translator being present (1)
• An interpreter produces no object code/file (1) because it translates and executes each line instead of saving translated code (1)
• The compiler's output can be saved/stored (1) and run again later, while interpreted code has to be translated again each time it is run (1)

Allow binary for machine code.

Allow executable/an executable for object code.

Do not accept responses about translating the whole program, reporting errors or the speed of execution.

Do not accept 'the interpreter translates/executes one line at a time' on its own: this is how it translates, not what it produces. It earns the development only when linked to no object code/translated file being produced.

Do not accept the interpreter producing object code/an executable.

Indicative content

The output of each type of translator

• A compiler translates the whole program in one go and produces object code.
• The object code is saved as an executable file, which is already in machine code so the processor can run it directly.
• An interpreter does not produce object code, so no translated file exists for the company to save and sell.
• An interpreter translates one line at a time and executes it immediately, but that translation is not kept.

Whether the program has to be translated each time it is run

• Compiled code is translated once, so the executable can be run as many times as the customer likes without being translated again.
• If the source code is edited, the whole program has to be compiled again to produce a new executable.
• An interpreted program is translated again every time it is run, so a customer who runs the program often waits for translation at every run.
• An executable runs faster than interpreted code because it is already in machine code.

What the customer needs on their computer to run the program

• A customer who installs the executable needs no compiler on their computer, so the program will run straight away.
• If the company supplied the source code instead, the customer would need an interpreter installed, and it would have to be an interpreter for their type of computer.
• A customer given only the executable does not have the source code, so cannot change the program.

Conclusion

• A compiler is the better choice for this company, because the executable can be sold and the customer runs it without it being translated again and without being given the source code.
• Using an interpreter would mean supplying the source code to customers and translating the program on every run.

Levels

• Level 0 (0 marks): No rewardable content.
• Level 1 (1–2 marks): Basic, independent points are made, showing elements of understanding of key concepts/principles of computer science. (AO1) The discussion will contain basic information with little linkage between points made or application to the context. (AO2)
• Level 2 (3–4 marks): Demonstrates adequate understanding of key concepts/principles of computer science. (AO1) The discussion shows some linkages and lines of reasoning with some structure and application to the context. (AO2)
• Level 3 (5–6 marks): Demonstrates comprehensive understanding of key concepts/principles of computer science to support the discussion being presented. (AO1) The discussion is well developed, with sustained lines of reasoning that are coherent and logically structured, and which clearly apply to the context. (AO2)

Level 3 responses must cover all three bullets for this company's program, including translating once rather than on every run, and reach a conclusion.

Do not accept 'a compiler fixes errors' (a compiler reports syntax errors at the end of translation, it does not fix them) or 'a compiler is easier to use' with no link to output, translation or the customer. Do not accept answers about translating to assembly language.