Edexcel GCSE Computer Science (1CP2) Exam Questions

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

• A read/write head moves over the surface of the disk (1) to read/write data by detecting or changing the magnetic alignment of areas of the surface (1)
• The head magnetises areas of the disk surface in different directions (1) so each area represents a binary 1 or 0 (1)
• Data is stored on concentric circles called tracks (1) which are divided into sectors (1)

Allow one mark for tracks/concentric circles on their own.

For the second mark in the first two bullets, the response must refer to the magnetic alignment/charge being detected or changed, not just that the head reads/writes data.

Do not award a mark for 'it is magnetic' or 'it stores data in binary' with no description of how the data is stored.

Do not accept descriptions of optical storage (e.g. a laser, pits and lands) or solid state storage (e.g. electric charges in chips).

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

• Carries out arithmetic operations/calculations, such as addition or subtraction (1) so that the result can be stored in a register (1)
• Carries out logical operations, such as comparing two data items (1) to see which one is greater/larger (1)
• Compares two data items (1) to decide whether a condition is true / which path a program takes next (1)

Allow the result of an arithmetic or logical operation being held/stored in a register, but only where the operation is named.

Do not accept answers that say the ALU stores data or results without naming an operation (registers/main memory store data).

Do not accept answers about controlling components, decoding instructions or timing (that is the control unit or the clock).

Do not award credit for 'it processes data' on its own; an arithmetic or a logical operation must be named.

An example on its own, e.g. 'it adds two numbers', does not earn a second mark; the second mark needs a linked development.

Indicative content

Why secondary storage is needed

• Secondary storage is non-volatile, so it keeps the operating system, applications and students' work when the power is turned off.
• It stores programs and files that are not currently in use, so they are not lost when the computer is switched off.
• It provides a larger capacity than primary storage for files such as students' work, videos and photographs.
• It allows each computer to keep many students' files and the software the school has installed.

The difference between primary and secondary storage

• Primary storage (RAM) is volatile and directly accessible by the CPU; secondary storage is non-volatile and not directly accessible by the CPU.
• RAM holds the data and instructions currently in use; secondary storage holds data and programs long term.
• Primary storage is faster but smaller and more expensive per gigabyte; secondary storage is slower but larger and cheaper.
• The school's computers need both: RAM to run the operating system and applications, and secondary storage to keep them when the computer is switched off.

A suitable type of secondary storage for the school's computers and a reason why it is suitable

• A solid state drive (SSD) is suitable because it has no moving parts, so it is durable and quiet, and has fast read/write speeds, which helps the computers start up quickly.
• A magnetic hard disk drive (HDD) is suitable because it is cheap and offers a very large capacity, which is useful for storing many students' files.
• Either type could be used; a small SSD for the operating system and applications plus a large HDD for files would balance speed and cost.

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

• Award credit for a type of secondary storage only when a reason is given that is linked to the school's computers; a named type alone (e.g. 'SSD') is not creditworthy. Do not accept RAM as secondary storage or the claim that secondary storage is the same as RAM. Do not accept CD/DVD/Blu-ray as the main storage for the school's computers because their capacity is too low and write speeds are slow.
• For Level 3, the answer must cover all three bullets and apply at least one point to the school's computers. A 6-mark answer is well developed with sustained reasoning and a justified choice; a 5-mark answer covers all three but with limited development or application. Comparisons of speed and cost between primary and secondary storage are creditworthy as part of the difference.

Indicative content

Stored program concept

• Instructions and data are stored together in the same main memory (RAM).
• Instructions are fetched one at a time from memory and executed in sequence.
• The program can be changed by loading different instructions into RAM.
• The CPU can only execute instructions that are in main memory.

Role of RAM

• RAM holds the program instructions and the data being used.
• The address of the next instruction is held in the program counter (PC).
• The instruction is fetched from RAM using the address bus.
• The data bus carries the instruction from RAM to the CPU.
• RAM is volatile, so programs are lost when power is off.
• RAM is directly accessible by the CPU, unlike secondary storage.

Benefits

• The same hardware can run many different programs.
• Programs can be loaded and changed quickly.
• No need to rewire the computer for a new task.
• Makes general-purpose computers possible.

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)