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 up to two marks for a linked description such as:

• The program's instructions (and the data it uses) are held in main memory/RAM (1) so the CPU fetches both the instructions and the data from that one memory (1)
• The CPU fetches the next instruction from main memory/RAM (1) using the address of the memory location that holds it (1)
• The CPU reads/fetches data from main memory/RAM (1) when an instruction needs it and writes the result back to main memory/RAM (1)
• The program's instructions are held in main memory/RAM while the program runs (1) and the CPU fetches them one at a time/one after another to be decoded and executed (1)

Allow 'memory' for main memory/RAM.

Allow 'gets' for fetches/reads.

For both marks, the development must say what the CPU does with the contents of main memory (fetches/reads/writes), not just that main memory is used.

Do not accept answers about the program being stored in secondary storage, such as on a hard drive, or about it being loaded from there.

Do not accept benefits such as the computer running faster or being easier for the user.

Do not accept naming CPU components (control unit, arithmetic logic unit, registers) or buses on their own, without saying what is stored or fetched.

Do not accept 'the computer stores data' on its own, without a link to the instructions of a program.

Indicative content

Magnetic storage

• A magnetic hard disk drive stores data on a magnetic platter that spins, with a read/write head on an actuator arm that moves over its surface.
• The read/write head magnetises small areas of the platter to represent binary 1s and 0s, and reads the magnetic pattern back when the data is needed.
• The data is held on concentric tracks that are divided into sectors. (Accept data being stored magnetically without further detail, but a vague 'it uses a magnet' is not enough for this point.)
• The platter and the read/write head are sealed inside the drive unit because of the precision needed.

Solid state storage

• A solid state drive stores data in flash memory chips and has no moving parts.
• A large electric current forces electrons through a barrier and traps them in a floating gate; the presence or absence of this trapped charge represents a 1 or a 0. (Accept either convention for which charge state represents a 1 and which represents a 0.)
• The charged cells are detected to read the data back. (Accept: the data can be erased and rewritten by applying a new current.)
• As there is no disk to spin to the correct position and no arm to move, data can be read from and written to solid state storage very quickly.

Suitability for the company's video files

• A magnetic HDD has a very large capacity and is generally cheaper per gigabyte than an SSD of the same capacity, which suits a company that stores many large video files.
• An SSD has very fast read/write speeds, so the company's large video files open and save quickly while they are being edited.
• An SSD has no moving parts, so it is more durable if the company's computers are carried between filming locations.
• A magnetic HDD could store finished videos as an archive and an SSD could hold the project being edited, so the company gets high speed while editing and low-cost capacity for storage.

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)

Additional guidance

• Level 3 answers must give accurate accounts of how data is stored on both magnetic and solid state storage and sustain a line of reasoning that applies at least one of them to the company's video files. An answer that covers only one storage type, or that describes both types without any application to the company, cannot go above Level 2.
• Do not accept descriptions of optical storage (pits and lands, a laser) as magnetic or solid state storage, and do not accept 'magnetic storage uses a laser' or 'solid state storage is volatile' or 'solid state storage is RAM'.