Edexcel GCSE Computer Science (1CP2) Exam Questions

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

• Stores programs (including the operating system) and data that are not currently in use (1) so that they can be loaded into RAM/main memory when needed (1)
• Keeps files/programs/data when the power is turned off (1) which happens because it is non-volatile (1)
• Stores files/data for backup or archiving (1) so that they can be recovered if the originals are lost/corrupted (1)

A correct role on its own earns one mark; the second mark requires a linked development.

Accept either order if both the role and the link are given.

Do not accept 'it is non-volatile' on its own, unless it is linked to keeping data when the power is turned off.

Do not accept answers that only name a storage type (magnetic, optical, solid state) without describing a role.

Do not accept responses that describe primary storage/RAM, e.g. storing the data/instructions the CPU is currently working on, or that secondary storage makes the computer run faster.

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

• It is a computer/processor built into a larger device (1) to carry out a single dedicated task/function (1)
• It is a combination of a processor, memory and input/output in one unit (1) that controls the device it is part of (1)
• It is a computer that forms part of another device (1) so it is not used as a general purpose computer (1)

Allow 'forms part of another device' or 'inside another device' for the first mark.

Do not award the second mark for a separate fact that is not linked to the first point, e.g. 'It is built into a device and it uses little power' would earn only the first mark (1).

Do not accept 'a small computer' on its own, with no reference to being part of another device or performing a dedicated task.

Do not accept 'a computer that controls a device' on its own, with no reference to it being built into/part of a larger device or carrying out a dedicated task.

Do not accept 'it performs a single dedicated task' on its own, with no reference to it being built into/part of a larger device.

Do not accept descriptions of a general purpose computer, e.g. 'it can run many different programs' or 'new software can be installed'.

Do not accept 'it is a system that is embedded in another system' as this repeats the term in the question.

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

• Decodes/interprets/translates the instruction (1) to work out what the instruction is/what operation is required (1)
• Sends control signals to the other components (1) so that the correct component carries out the instruction (1), e.g. the ALU/main memory
• Controls the fetch of the instruction from main memory (1) because the address of the next instruction is sent via the address bus (1)
• Controls the fetch of the next instruction from main memory (1) by sending a control signal/read signal to main memory (1)

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

For the decode point, 'decodes the instruction' alone gains 1 mark; a second mark needs the purpose of decoding, i.e. working out what the instruction is/what operation is required.

Do not accept 'it controls the CPU' on its own, without naming a task in the cycle.

Do not accept 'it fetches the instruction from memory' on its own, as this describes the fetch step rather than the control unit's role; credit only if linked to controlling/signalling the fetch.

Do not accept carrying out arithmetic/logical operations, as these are carried out by the ALU, or holding the address of the next instruction, as this is the program counter.

Do not accept storing the instruction in a register (e.g. MAR/MDR), as this is not the role of the control unit.