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Edexcel GCSE Computer Science (1CP2) Exam Questions

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3 questions · 9 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.

2Short recall2 marksStored Program Computers Swap Remove

The central processing unit (CPU) contains an arithmetic logic unit (ALU).

State two types of operation carried out by the ALU.

[2 marks]
Mark scheme

Award one mark for any of the following up to a maximum of two marks:

  • An arithmetic operation, e.g. addition/subtraction/multiplication/division (1)
  • A logical operation, e.g. comparing two values (is A > B?) / using AND, OR, NOT (1)

Do not accept decoding instructions, fetching instructions or controlling the timing of the CPU, as these are carried out by the control unit.

Example answers and how they were marked
Full marks2/2

It carries out arithmetic operations such as addition and subtraction, and logical operations such as comparing two values to see if one is greater than the other.

Why: Arithmetic operation (1) and logical operation (1).

Some marks1/2

It adds numbers together and works out the result.

Why: Arithmetic operation, addition (1). No logical operation.

No marks0/2

It decodes the instructions that have been fetched from main memory.

Why: Decoding and fetching are the control unit's role; the mark scheme's do-not-accept line covers this.

3Discuss6 marksPrimary Memory Swap Remove

A school is buying new computers for its IT room. The computers the technician has ordered have 16 GB of RAM and a large hard drive.

Discuss why main memory (RAM) is needed for programs to run on these computers.

Your answer should include:

  • the role of RAM in the stored program concept
  • what happens to a program when it is opened
  • why the CPU cannot execute a program directly from secondary storage.
[6 marks]
Mark scheme

Indicative content

the role of RAM in the stored program concept

  • In the von Neumann stored program concept, a program's instructions and the data it uses are held together in main memory.
  • RAM holds the instructions and data of the program that the CPU is currently processing.
  • The CPU fetches each instruction from RAM during the fetch-decode-execute cycle, so a program must be in RAM before it can be run.
  • RAM is directly accessible by the CPU, so instructions can be fetched quickly enough for the CPU to keep working.

what happens to a program when it is opened

  • When a program is opened, a copy of its instructions and data is transferred from secondary storage, such as the hard drive, into RAM.
  • The operating system loads the program into RAM so that the CPU can start fetching and executing its instructions.
  • When the program is closed, it is removed from RAM, and the space it used is free for another program.
  • If a computer does not have enough RAM, the program may not open, or another open program has to be closed first.

why the CPU cannot execute a program directly from secondary storage

  • Secondary storage, such as a hard disk drive, is much slower to access than RAM.
  • The CPU can process instructions much faster than secondary storage can supply them, so the CPU would have to wait and would not be working at full speed.
  • RAM is fast electronic memory with no moving parts, so data can be read from it in a fraction of the time taken by a magnetic hard disk drive.
  • Running the school's programs directly from secondary storage would make the computers in the IT room very slow to use.

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 both the role of RAM in the stored program concept and the speed difference between RAM and secondary storage, with a reason such as the CPU having to wait for instructions.
  • Answers that make only basic, independent points, such as what RAM is, that a program is copied into RAM when it is opened, or that RAM is faster than a hard drive, without linking them to explain why the CPU would have to wait for instructions, are limited to Level 1.
  • Do not accept statements that RAM is permanent storage, that RAM replaces secondary storage, or that secondary storage is read-only.
Example answers and how they were marked
Full marks6/6

The computers need RAM because of the von Neumann stored program concept, in which the instructions of a program and the data it uses are both held in main memory. When a student opens a program on one of the new computers, the operating system copies it from the hard drive into RAM. The CPU then fetches each instruction from RAM in the fetch-decode-execute cycle, so the program must be in RAM before it can be run. The CPU cannot execute a program directly from secondary storage because a hard disk drive is much slower than RAM. It has moving parts and a much lower transfer rate, so the CPU would often have nothing to do while it waited for the next instruction. RAM is fast electronic memory that the CPU can read directly, which is why 16 GB of RAM lets the school run several programs at once and still keep the CPU working at full speed.

Why: Comprehensive understanding: the stored program concept is explained (instructions and data held in main memory), the program being opened is linked to it, and the speed difference is developed with the reason that the CPU would wait for instructions, all applied to the school's computers. Level 3.

Some marks2/6

RAM is the main memory of the computer. It stores the programs and data that are being used at the moment. When you open a program it is copied into RAM, and the CPU fetches instructions from RAM. RAM is faster than the hard drive, so a program runs better from RAM. Having 16 GB means the school can have more programs open at once.

Why: Basic, independent points only: what RAM is, that a program is copied into RAM when it is opened, that the CPU fetches instructions from RAM, and that RAM is faster than a hard drive. None is linked to the stored program concept or developed to explain why the CPU would have to wait for instructions, so Level 1, 2 marks.

No marks0/6

RAM is the permanent storage inside the computer, like a hard drive. The school needs 16 GB of RAM so that all the students' files can be saved permanently. When a program is opened, it is copied from RAM to the CPU. The CPU cannot execute from secondary storage because secondary storage is read-only.

Why: No creditworthy points. RAM is described as permanent storage, files are said to be saved permanently in RAM, a program is said to be copied from RAM to the CPU, and secondary storage is said to be read-only. All are the misconceptions listed in the Do not accept guidance, so Level 0.

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