Edexcel GCSE Computer Science (1CP2) Exam Questions

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

• (Storage that is) non-volatile / keeps its data when the power is turned off (1)
• (Storage that is) used to store programs and data/files (for later use) (1)
• (Storage that is) not directly accessible by the CPU / not directly accessed by the CPU (1)

Allow both the non-volatile point and the stores programs and data point from one sentence if each idea is clearly stated, e.g. 'non-volatile storage that holds programs and data'.

Allow accessed via the CPU / must be copied into RAM before the CPU can use it for the third point.

Do not accept volatile / loses its data when the power is turned off.

Do not accept a description of primary storage, such as RAM or ROM.

Do not accept capacity.

Do not accept an example device on its own (e.g. hard disk drive).

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

• Data is stored on (flash) memory chips/cells (1) as a pattern of electrical charges (1)
• A current/voltage forces electrons through a barrier (1) so that they are trapped (or not trapped) to hold/represent a value (1)
• Cells with a trapped charge and cells with no trapped charge (1) represent 1s and 0s/binary (1)
• The trapped charge remains when the power is turned off (1) so the data is not lost/it is non-volatile (1)

Do not accept responses that describe magnetic storage, e.g. magnetised platters, spinning disks or read/write heads, or optical storage, e.g. lasers, pits and lands.

Do not award a mark for 'it is solid state' or 'it has no moving parts' without a description of how the data is stored.

Do not award a mark for restating the stem, e.g. 'a laptop uses an SSD' or 'an SSD uses flash memory'.

'Data is stored as electrical charges' on its own, with no reference to memory chips/cells or to how the charge is held, earns a maximum of one mark (1).

A response that only describes electrons being trapped, with no link to how the value/data is represented, earns one mark (1). The second mark needs a link such as trapped and not trapped charge representing 1s and 0s, or the trapped charge being kept so the data is not lost.

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.

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

• The CPU can only fetch/read instructions from main memory/RAM (1) so the instructions of a running program must be copied/loaded into RAM before they can be executed (1)
• RAM is faster to access than secondary storage (1) so the instructions can be fetched quickly enough for the CPU to execute them (1)
• The CPU needs the instructions in RAM to fetch and execute them (1) because the fetch-decode-execute cycle reads each instruction from main memory/RAM (1)
• The address of the next instruction is sent to RAM on the address bus (1) so the instruction can be transferred to the CPU/registers for decoding/execution (1)

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

Allow the point and reason in either order if they are linked.

Do not accept answers that only say the CPU needs instructions, or that RAM is faster, without linking this to fetching/executing the instructions.

Do not accept answers that only say RAM holds data and instructions without linking this to the fetch-decode-execute cycle.

Do not accept 'RAM is permanent/non-volatile storage, so the instructions are kept safe' - RAM is volatile.

The response does not need to name the address bus or the fetch stage for full marks; a linked reason that explains why instructions must be in RAM (for example, the CPU can only fetch from RAM, or RAM is faster than secondary storage) is enough.