Edexcel GCSE Computer Science (1CP2) Exam Questions

• A Blu-ray Disc (1)
• The only correct answer is A. The correct answer is Blu-ray Disc.
• B is not correct because a CD stores less data than a Blu-ray Disc, up to about 700 MB
• C is not correct because a DVD stores less data than a Blu-ray Disc, up to about 4.7 GB (single-layer) or 8.4 GB (dual-layer)
• D is not correct because magnetic tape is not an optical storage medium

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

• It controls the motors/rotors (1) so that the drone can take off, hover, turn and land (1)
• It keeps the drone stable/level automatically (1) by taking readings from a sensor (accelerometer/gyroscope/GPS) (1)
• It receives signals from the remote control (1) and changes the speed of the motors to steer the drone (1)
• It monitors the battery level (1) and brings the drone back to the ground before the battery runs out (1)

The development must relate to the function given in the point.

Accept a named function that the embedded system controls, e.g. 'it keeps the drone level', as the first mark (1).

Award the second mark only when the development gives a specific outcome or detail of that function, e.g. 'so that the drone can take off, hover, turn and land' or 'by changing the motor speeds to keep it level'.

Do not award the second mark for a generic outcome such as 'so it works', 'so it can fly' or 'so the drone moves'.

A bare 'it controls the motors so it can fly' therefore earns the first mark only.

Allow any other specific function of a drone that is carried out by the embedded system.

Do not accept 'it flies the drone' / 'it is the drone's brain' / 'it makes the drone work' without a named function being controlled.

Do not accept answers that describe the user or the remote control flying the drone with no function carried out by the embedded system.

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

• A temperature sensor measures/reads the temperature in the greenhouse (1) which the processor compares with the value stored in the system (1)
• The heater is switched on (1) when the temperature reading goes below the value stored in the system (1)
• A fan/vent/window is opened/a cooler is switched on (1) when the temperature reading goes above the value stored in the system (1)
• The temperature is checked/measured continuously (1) so the heater/fan is switched on or off as soon as the temperature changes (1)

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

Allow one mark for a correct point on its own without a linked reason, e.g. 'a temperature sensor measures the temperature'.

Do not award 'the embedded system controls/keeps the temperature correct' as this repeats the question.

Do not accept naming a device without saying what it does, e.g. 'the greenhouse has a thermostat'.

Indicative content

Fetching and decoding an instruction

• The register that holds the address of the next instruction (the program counter) contains the address of the instruction to be fetched.
• This address is sent to main memory (RAM) and the instruction is copied from main memory into a register inside the CPU.
• The program counter is updated so that it holds the address of the next instruction in the program.
• The control unit decodes the instruction that has been fetched, working out which operation is required and which data or registers are needed.
• The control unit sends control signals to coordinate the other components as the instruction is carried out.
• The control unit decides what happens next, for example after a comparison it decides whether the next instruction is the following one or a jump.

The arithmetic logic unit (ALU) executes an instruction

• The control unit directs the arithmetic logic unit (ALU) to carry out the operation.
• The ALU performs arithmetic operations such as addition, subtraction, multiplication and division, for example adding two values in a program written by the class.
• The ALU performs logical operations such as comparing two values to see if they are equal or whether one is greater than the other.
• The result of the operation carried out by the ALU is passed back and stored in a register.
• The ALU operates on data that has been fetched from main memory; it does not fetch the instruction and it does not decide which instruction is next.

Registers

• Registers are small, very fast memory locations inside the CPU.
• They hold the data, addresses and results that the CPU is working on during the cycle.
• Registers are used in every stage of the cycle, not only when the ALU produces a result.
• Because registers are inside the CPU they can be read and written much faster than main memory during the cycle.

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)
• A Level 3 answer must link the roles of all three components to the fetch, decode and execute stages. An answer that links only one component to a stage, with the other points listed separately, is Level 1 (1–2 marks); an answer that links two of the components to stages is Level 2 (3–4 marks). A point repeated under more than one heading is credited once only.
• Accept 'the program counter', 'the address register' or 'a register holding the address of the next instruction' as the register that holds the address of the next instruction. Do not accept 'the control unit performs the calculations', 'the ALU controls the timing of the CPU' / 'the ALU sends the clock signal' or 'registers are in main memory (RAM)'.