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Edexcel GCSE Computer Science (1CP2) Exam Questions

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3 questions · 14 marks

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1Explain2 marksEmbedded Systems Swap Remove

An engine control unit (ECU) in a car is an embedded system.

Explain one benefit of using an embedded system for the engine control unit instead of a general purpose computer.

[2 marks]
Mark scheme

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

  • (The ECU) is more reliable/less likely to crash (1) because it only runs the one program/has a single purpose (1)
  • (The ECU) cannot be affected by other software/viruses (1) because it cannot run other software/it can only run the program it was made for (1)
  • (The ECU) is cheaper (1) because it has limited processing resources/less memory/simple components (1)
  • (The ECU) uses less power (1) because it has limited processing resources/a simpler processor (1)
  • (The ECU) is smaller (1) because it has fewer components/less memory than a general purpose computer (1)

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

A suitable benefit stated on its own earns one mark.

Do not accept a description or a location given as the reason, e.g. 'because it is part of the car', 'because it is inside the engine', 'because it is embedded'.

Do not accept a description of an embedded system on its own as the benefit, e.g. 'it does one specific job' or 'it is part of the car'.

Do not accept 'it is faster'/'it has a more powerful processor' as embedded systems have limited processing resources.

Example answers and how they were marked
Full marks2/2

It is more reliable than a general purpose computer (1) because it only runs the one program so it will not crash and stop the engine working (1).

Why: Benefit stated (1) with a linked reason (1); the reason shows why only running one program makes it reliable.

Some marks1/2

It is more reliable (1) because it is part of the car's engine (1).

Why: Only the benefit earns a mark (1); being part of the car is a location, not a linked reason why it is reliable.

No marks0/2

It is faster than a general purpose computer (0) because it is embedded in the engine (0).

Why: Misconception that an embedded system is faster; embedded systems have limited processing resources, so neither point nor reason is creditworthy.

2Discuss6 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.

3Discuss6 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.

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

Build a paper on this topic 56
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

Build a paper on this topic 77
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

Build a paper on this topic 124
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

Build a paper on this topic 37
Low and High Level Languages 19 questions Translators 18 questions

4.1 Networks

Build a paper on this topic 138
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

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