Edexcel GCSE Computer Science (1CP2) Exam Questions

Award one mark for any of the following up to a maximum of two marks:

• An arithmetic operation, e.g. addition/subtraction/multiplication/division (1)
• A logical operation, e.g. comparing two values (is A > B?) / using AND, OR, NOT (1)

Do not accept decoding instructions, fetching instructions or controlling the timing of the CPU, as these are carried out by the control unit.

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

• The processor/CPU can only execute machine code/binary instructions (1) so the assembly instructions must be converted into machine code before the program can run (1)
• Each assembly instruction/mnemonic matches/corresponds to one machine code instruction (1) so each line must be replaced with the machine code the processor executes (1)
• The program is written using mnemonics (1) that must be translated into machine code for the processor to carry out the instructions (1)
• The hardware/processor does not understand assembly language directly (1) so it must be translated into machine code that the processor can execute (1)

Do not accept 'assembly language is a low-level language'.

Do not accept 'it is hard to understand' or 'it is not English'.

Do not accept benefits, such as 'machine code runs faster' or 'the program will run more quickly'.

Do not accept 'an assembler/a translator converts it' on its own, with no reference to the processor only being able to execute machine code/binary.

Do not accept responses about high-level languages or about compilers/interpreters.

Indicative content

What a device driver is and how the operating system uses it

• A device driver is a program that controls a peripheral device such as a graphics tablet by communicating with the operating system.
• The driver translates instructions from the operating system into signals that the graphics tablet understands, and passes the artist's pen movements back to the operating system.
• The operating system loads the driver into memory when the tablet is connected, so that it can then send data to the tablet and receive input from it.
• Without a driver the operating system cannot control the tablet, so the tablet does not work.

Why each peripheral needs its own driver

• Every make and model of peripheral uses its own set of commands, so a driver is written for that particular device.
• The drivers already installed for the studio's older tablets do not work with the new model, even though both are graphics tablets.
• An operating system includes drivers for many common devices, but it does not have one for a brand new model.
• The correct driver means the pen movements are received by the computer in the form the drawing program expects.

What must be done before an artist can use a new tablet

• The new tablet is supplied with its driver on a disc or as a download, and it must be installed on each computer.
• The operating system may need to be updated so that it recognises the new model.
• The driver must be enabled or selected for the tablet once it is installed.
• Drivers are updated later to fix faults or to improve performance.
• If the correct driver is not installed, the tablet does not work or some of its features are not available.

Additional guidance

• Level 3 responses must explain why a driver is specific to a device and what must be done before an artist can use a new tablet, as well as describing what a driver is, all applied to the studio.
• Responses that only state what a driver is, or that state a driver must be installed without explaining why the tablet needs its own driver, are limited to Level 1.
• Accept 'software', 'program' or 'set of instructions' for a driver.
• Do not accept a device driver described only as a cable or a physical connection.
• Do not accept the claim that all drivers are already built into the operating system, or that one driver works for every graphics tablet.

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)

Indicative content

How each translator deals with a syntax error

• An interpreter stops as soon as it finds a syntax error and displays an error message.
• With an interpreter, the lines before the error have already been executed, so the student can see how far the program got before it stopped.
• A compiler reports errors at the end of translation, so the student gets a list of all the syntax errors in the program in one go.

How much of the program is translated at a time

• An interpreter translates one line at a time and executes each line immediately.
• A compiler translates the whole program in one go before any of it is run.
• A compiler produces object code, so after every change the whole program must be compiled again before the student can run it.
• An interpreter produces no object code, so the student does not have to wait for the whole program to be translated before it runs.

How this affects the student's testing

• An interpreter suits this student because the program can be run straight away after each small change.
• The interpreter stops at the first error found, so the student fixes that error and runs the program again, but may only find the next error on the next run.
• Reporting every error at the end of compilation means the student can fix several errors at once, but cannot run the program until the whole program compiles.
• The student should use an interpreter while testing, and compile the finished program once it works.

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 relate the way each translator works to the student's testing, not just describe the two translators.

Do not accept answers about run-time or logic errors where no comparison of the translators is made.