Edexcel GCSE Computer Science (1CP2) exam questions

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6 questions · 19 marks

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1Short recall1 markPrimary Memory Swap Remove

Computers use RAM to store the data and instructions that are in use.

Name the term used to describe memory that loses its contents when the power is switched off.

[1 mark]

Mark scheme

Award one mark for:

Volatile (1)

Allow volatile memory / it is volatile.

Do not accept non-volatile, ROM, RAM or temporary/short term memory on their own, as these are not the term asked for.

Example answers and how they were marked

Full marks1/1

Volatile

Why: Correct term for memory that loses its contents when the power is switched off (1).

No marks0/1

Temporary memory

Why: Describes what such memory does but is not the term asked for; 'temporary memory' is on the Do not accept line, so no mark.

No marks0/1

Non-volatile

Why: Non-volatile memory keeps its contents when the power is switched off, the opposite of what the question describes; it is explicitly not accepted.

2Describe2 marksSecondary Memory Swap Remove

Computers use secondary storage.

Describe the role of secondary storage.

[2 marks]

Mark scheme

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.

Example answers and how they were marked

Full marks2/2

Secondary storage stores programs and data that are not currently in use so that they can be loaded into RAM when they are needed.

Why: Role point (1) linked to loading into RAM when needed (1).

Some marks1/2

It stores files and programs that are not currently in use.

Why: Correct role on its own earns one mark (1); no linked development, so the second mark is not awarded.

No marks0/2

It holds the data and instructions the CPU is working on so the computer runs faster.

Why: Describes primary storage/RAM and a speed benefit, which the mark scheme does not accept; no role of secondary storage is given.

3Describe2 marksSecondary Memory Swap Remove

A laptop uses a solid state drive (SSD) for secondary storage.

Describe how data is stored on a solid state drive.

[2 marks]

Mark scheme

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.

Example answers and how they were marked

Full marks2/2

A current is used to force electrons through a barrier so that they become trapped, and a cell with a trapped charge or a cell with no trapped charge represents a 1 or a 0.

Why: Linked description: a current forces electrons through a barrier (1) and trapped/not trapped charge represents 1s and 0s (1).

Some marks1/2

The data is stored in flash memory chips.

Why: Gives the creditworthy point that data is stored on flash memory chips (1) but does not develop it, e.g. by saying the data is held as electrical charges or by describing trapped electrons.

No marks0/2

The data is stored as magnetised areas on a spinning platter.

Why: This describes magnetic storage, which the mark scheme says not to accept for a solid state drive.

4Explain2 marksFetch Decode Execute Cycle Swap Remove

The von Neumann architecture is used in most computers.

Explain one feature of the von Neumann stored program concept.

[2 marks]

Mark scheme

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

The instructions/program instructions and data are stored together in main memory/RAM (1) so the CPU can fetch each instruction (from its address) and execute it (1)
The instructions/program instructions are held in main memory/RAM (1) rather than being built into/part of the hardware, so the computer does not need to be rewired/rebuilt to run a different program (1)
The next instruction to be executed/instruction is held in main memory/RAM (1) so the CPU can fetch it using its address before it is decoded and executed (1)

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

A point/statement on its own can only earn one mark.

Do not accept a response that only refers to data being stored in main memory/RAM without referring to the instructions/program instructions.

Do not accept instructions/programs being stored on the hard disk/backing store.

Do not accept 'the program is stored in memory' without saying that it is the instructions/program instructions that are stored there.

Example answers and how they were marked

Full marks2/2

Both the instructions of the program and the data it uses are stored together in the same main memory, so the CPU can fetch each instruction in turn and execute it.

Why: Linked point (1) and reason (1).

Some marks1/2

The instructions of the program are stored in main memory.

Why: Point only (1); no linked reason about fetching/executing the instructions.

No marks0/2

The program is stored on the hard disk and is copied into the CPU when it is run.

Why: Misconception covered by the 'Do not accept' line: the instructions must be stored in main memory/RAM, not on the hard disk/backing store, for the CPU to fetch them.

5Discuss6 marksFetch Decode Execute Cycle Swap Remove

A small robotics company is designing a new robot. The robot's computer uses von Neumann architecture. The engineers are explaining how programs are stored and run.

Discuss how the von Neumann stored program concept and main memory (RAM) are used during the fetch-decode-execute cycle.

Your answer should include:

what is meant by the stored program concept
the role of RAM in the cycle
why the stored program concept is useful.

[6 marks]

Mark scheme

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)

Example answers and how they were marked

Full marks6/6

The von Neumann stored program concept means that both the program instructions and the data are stored together in the same main memory, RAM. During the fetch-decode-execute cycle, the CPU fetches an instruction from RAM, decodes it in the control unit, and then executes it. The program counter holds the address of the next instruction, and this address is sent along the address bus to RAM. RAM then returns the instruction along the data bus to the CPU. RAM is volatile, so it only holds the program while the robot is powered on. The stored program concept is useful because the robot's computer can run different programs without changing any hardware; new instructions can simply be loaded into RAM. This makes the computer general-purpose and flexible.

Why: Comprehensive understanding: defines stored program concept, explains RAM role with PC, address bus and data bus, applies to robot, and gives benefits. Sustained lines of reasoning. Level 3.

Some marks3/6

The stored program concept is when instructions and data are stored in RAM. The CPU fetches instructions from RAM. The program counter keeps the address of the next instruction. RAM holds the program. The benefit is that you can change the program without rewiring the computer.

Why: Adequate understanding: correct basic points about stored program concept and RAM, with some linkage, but little development or application to the robot's fetch-decode-execute cycle. Level 2.

Some marks1/6

The von Neumann stored program concept is that the CPU uses RAM to store the program. The fetch-decode-execute cycle fetches, decodes and executes. RAM is random access memory. The benefit is that it is fast.

Why: Basic independent points only; no real linkage or application to the robot. Level 1.

6Discuss6 marksStored Program Computers Swap Remove

A college is replacing the computers in its IT suite. The technician tells the students that the new computers use the von Neumann stored program concept.

Discuss the von Neumann stored program concept and the role of the CPU and main memory (RAM) in the fetch-decode-execute cycle.

Your answer should consider:

the role of main memory (RAM)
the role of the CPU components (control unit, arithmetic logic unit, registers and clock)
the role of the address, data and control buses.

You do not need to consider how clock speed affects performance.

[6 marks]

Mark scheme

Indicative content

Stored program concept

The stored program concept means that the program instructions and the data the program is using are both held in the same main memory (RAM).
The CPU fetches an instruction from main memory, the control unit decodes it and the instruction is executed, and this is repeated in the fetch-decode-execute cycle.
The program is stored as a set of binary instructions, so a different program can be run on the college's new computers by loading different instructions into RAM rather than by changing any hardware.
Instructions are usually carried out one at a time, in the order in which they are stored, which is suitable for the computers in the IT suite that each run one piece of software at a time.

Main memory (RAM)

Main memory (RAM) holds the instructions and the data that the CPU is currently using.
RAM is directly accessible by the CPU, so the required instruction or item of data can be fetched quickly during the fetch stage of the cycle.
RAM can be read from and written to while a program is running, so the results produced by the students' work can be stored back into memory.
RAM is volatile, so its contents are lost when the power is turned off, and the college's computers will have empty RAM each time they are started.

CPU components

The control unit decodes each instruction and coordinates the timing and control of the other parts of the CPU, so it directs the fetch-decode-execute cycle.
The arithmetic logic unit (ALU) carries out arithmetic operations and logical comparisons on the data, for example working out a student's total mark in a spreadsheet.
Registers are small, fast storage locations inside the CPU that hold the address of the next instruction, the instruction being decoded and the data being worked on.
The clock sends a regular signal that synchronises the actions of the CPU, so each step of the cycle is carried out in time with the clock.

Buses

The address bus is one way, from the CPU to main memory, and carries the address of the memory location that the CPU wants to read from or write to.
The data bus carries the instruction or the data between the CPU and main memory, so it is used to bring an instruction to the CPU in the fetch stage.
The control bus carries control signals such as read and write, so the CPU can tell main memory whether it is reading an instruction or writing data.

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 responses must cover the role of main memory (RAM) and the role of the CPU components or the buses during the fetch-decode-execute cycle, as well as the stored program concept.
Do not accept RAM described as being inside the CPU, or as non-volatile, or any point about how clock speed affects performance, because the question excludes it.

Example answers and how they were marked

Full marks6/6

The von Neumann stored program concept means that the program instructions and the data the program is using are both held in the same main memory (RAM). This means each of the college's new computers can run any piece of software simply by loading a different set of instructions into its RAM, with no change to the hardware. The CPU fetches an instruction from RAM, the control unit decodes it and the instruction is executed, and this repeats in the fetch-decode-execute cycle. RAM holds the instructions and data that the CPU is currently using and is directly accessible by the CPU, so they can be fetched quickly, but it is volatile, so the contents are lost when a computer is switched off at the end of the day. During the fetch stage, the address bus carries the address of the instruction in RAM, the data bus carries the instruction back to the CPU, and the control bus carries the control signals, such as read, that tell main memory what to do. Registers inside the CPU hold the address of the next instruction and the data being worked on, the clock sends a regular signal so that every step of the cycle happens in time, and the ALU carries out the arithmetic and logical operations needed by the students' work in the IT suite.

Why: Level 3: accurate stored program concept linked to loading software on the college's computers, the role of RAM including volatility, and the roles of the address, data and control buses, registers, clock and ALU, all applied to the situation.

Some marks3/6

The stored program concept means that the program instructions and the data the program is using are stored together in the same memory. The CPU fetches an instruction from main memory, decodes it and then executes it. Main memory (RAM) holds the instructions and data that the CPU is using and it can be read from and written to, so the CPU can get at them quickly. RAM is volatile, so its contents are lost when the computer is switched off.

Why: Level 2: an adequate account of the stored program concept and the role of RAM, with one line of reasoning (fetch, decode, execute) and the volatility point, but no coverage of the CPU components or the buses and no application to the college's computers, so it stays at the lower end of Level 2.

Some marks1/6

In von Neumann architecture the CPU fetches and decodes instructions one at a time. RAM is the memory inside the CPU that stores the program so that it is not lost when the computer is switched off. The clock speed makes the CPU faster so the fetch-decode-execute cycle runs more quickly.

Why: Level 1: one basic point about the CPU fetching and decoding instructions from memory; RAM is wrongly placed inside the CPU and described as non-volatile and the clock speed point is excluded by the question, so neither is credited.

Edexcel GCSE Computer Science (1CP2) Exam Questions

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2.1 Binary

2.2 Data representation

2.3 Data storage and compression

3.1 Hardware

3.2 Software

3.3 Programming languages

4.1 Networks

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