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Edexcel GCSE Computer Science (1CP2) Exam Questions

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4 questions · 8 marks

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1Describe2 marksStored Program Computers Swap Remove

A computer is based on the von Neumann stored program concept.

Describe how the CPU uses main memory (RAM) during the fetch-decode-execute cycle.

[2 marks]
Mark scheme

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.

Example answers and how they were marked
Full marks2/2

The program's instructions and the data it uses are both held in the same main memory (RAM), so the CPU can fetch the instructions and the data it needs from that one memory.

Why: Linked point (1) that instructions and data are stored together in main memory, with the development (1) that the CPU fetches both from the same memory.

Some marks1/2

The CPU fetches the instructions from main memory so that they are processed more quickly.

Why: The first point earns (1) for the CPU fetching instructions from main memory. The second statement is a benefit (speed), which the 'Do not accept benefits' line rules out, so it earns nothing.

No marks0/2

The control unit decodes each instruction and the ALU carries out the calculations.

Why: Both statements name CPU components without saying what is stored, fetched or written, which the mark scheme tells examiners not to accept, so neither earns a mark.

2Describe2 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.

3Explain2 marksFetch Decode Execute Cycle Swap Remove

The CPU carries out the fetch-decode-execute cycle.

Explain one reason why the address bus is used in the fetch stage of the fetch-decode-execute cycle.

[2 marks]
Mark scheme

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

  • The address bus carries the address of the next instruction (1) so the CPU can locate/fetch it from main memory/RAM (1)
  • The address bus carries the address of the memory location to be read (1) so the instruction/data stored there can be located/accessed (1)
  • The CPU needs to know where the next instruction is stored (1) so the address bus sends the address to main memory/RAM (1)

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

Allow 'from the program counter/PC' as part of the point for one mark, e.g. the address bus carries the address from the program counter (1), but the second mark needs the destination or purpose (e.g. to locate/fetch the instruction in main memory/RAM).

Do not award the second mark for naming the program counter/PC alone.

Do not accept answers that say the address bus carries data/instructions from main memory to the CPU, as these travel on the data bus.

Do not accept answers that say the address bus stores the address.

Do not allow an answer that only restates that the address bus carries addresses without saying which address or why it is needed.

Example answers and how they were marked
Full marks2/2

The address bus carries the address of the next instruction from the program counter to main memory, so that the CPU can locate the instruction that is to be fetched.

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

Some marks1/2

The address bus carries the address of the next instruction from the program counter.

Why: Point only (1); the second mark is not awarded because the destination/purpose of locating or fetching the instruction is missing.

No marks0/2

It carries the instruction from main memory back to the CPU so that it can be decoded.

Why: Misconception: instructions travel on the data bus, which the mark scheme's Do not accept line covers.

4Explain2 marksSecondary Memory Swap Remove

A hard disk drive stores data on a spinning magnetic platter.

Explain how data is read from a magnetic hard disk.

[2 marks]
Mark scheme

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

  • The read/write head moves over the surface of the platter (1) and detects whether each area of the disk is magnetised (1)
  • The platter spins/rotates (1) so the read/write head can pass over the whole surface/tracks of the disk (1)
  • The pattern of magnetised and non-magnetised areas detected by the read/write head (1) is read as binary 1s and 0s (1)
  • The drive head detects the direction of magnetisation of each area (1) so the data can be read as binary (1)

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

Allow one mark for stating that data is read magnetically / that the read/write head detects the magnetisation of the disk without a linked reason.

Do not accept answers that describe how data is written to the disk, such as the head magnetising the platter, rather than how it is read.

Do not accept 'a laser reads the pits and lands' - this describes optical storage, not magnetic storage.

Example answers and how they were marked
Full marks2/2

The platter rotates so the read/write head passes over the whole surface of the disk and it detects whether each area is magnetised or not. The pattern of magnetised areas is then read as 1s and 0s.

Why: Linked point (1) rotation of the platter with reason (1) the head reaches the whole surface, and the second line about magnetised areas is also present.

Some marks1/2

The read/write head detects the magnetic charges on the disk.

Why: Allow line (1): states the head detects the magnetisation of the disk, but gives no linked reason (e.g. the platter rotating so the head covers the whole surface), so only one mark.

No marks0/2

A laser shines onto the disk and reads the pits and lands, then the data is sent to the CPU.

Why: Describes optical storage. Do not accept 'a laser reads the pits and lands' - a magnetic disk is read by a head detecting magnetisation.

Questions by topic

2.1 Binary

Build a paper on this topic 58
Adding Binary Numbers 6 questions Binary and Hexadecimal Basics 10 questions Binary Shifts 6 questions Binary to Denary Conversion 6 questions Binary to Hexadecimal Conversion 6 questions Denary to Binary Conversion 6 questions Denary to Hexadecimal Conversion 6 questions Denary to Negative Binary Conversion 6 questions Hexadecimal to Binary Conversion 6 questions

2.2 Data representation

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Character Sets 18 questions Images 19 questions Sound 19 questions

2.3 Data storage and compression

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Compression 18 questions Units & Conversion 6 questions

3.1 Hardware

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Embedded Systems 17 questions Fetch Decode Execute Cycle 15 questions Primary Memory 15 questions Secondary Memory 15 questions Stored Program Computers 15 questions

3.2 Software

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File Management 18 questions Memory Management 16 questions Peripheral Management 11 questions Process Management 12 questions Purpose & Function of Operating Systems 17 questions Software Basics 13 questions User Management 18 questions Utility Software 19 questions

3.3 Programming languages

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Low and High Level Languages 19 questions Translators 18 questions

4.1 Networks

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Addressing 16 questions LANs & WANs 16 questions Network Speed 5 questions Packet Switching 16 questions Protocols & Layers 17 questions The Internet 16 questions Topologies 17 questions Wired Connections 17 questions Wireless Connections 18 questions

4.2 Network security

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Network Security Risks 18 questions Preventing Network Security Risks 18 questions

5.1 Environmental

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E-waste 17 questions Manufacturing Technology 19 questions

5.2 Ethical and legal

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Data Protection Act 17 questions Impact of AI 18 questions Intellectual Property 18 questions Software Licences 18 questions

5.3 Cybersecurity

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Malware 18 questions Social Engineering 18 questions

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