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Edexcel GCSE Computer Science (1CP2) Exam Questions

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4 questions · 12 marks

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1Short 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.

2Describe2 marksMemory Management Swap Remove

A program is stored on secondary storage before it is run.

Describe how the operating system manages memory when a program is started.

[2 marks]
Mark scheme

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

  • The program (and its data) is copied/loaded from secondary storage into main memory/RAM (1) so that the CPU can fetch/execute its instructions (1)
  • An area of main memory is allocated/reserved for the program (1) that is large enough to hold the program and its data (1)
  • The operating system checks that there is enough free main memory (1) before the program can be started/loaded, otherwise it cannot run/an error is reported (1)
  • The operating system keeps a record of the memory addresses used by the program (1) so that its instructions and data can be found when it runs (1)

Allow 'loaded into RAM', 'stored in memory' and 'put into main memory' as equivalent to copied into main memory.

A single statement that the program is loaded/stored in main memory, with no linked development, can be given one mark only.

Do not accept descriptions of the CPU fetching/executing instructions that do not refer to the operating system loading or allocating memory.

Do not accept responses about virtual memory (moving processes to secondary storage) or about which process runs next on the CPU.

Do not accept the program being run from secondary storage/hard disk.

Example answers and how they were marked
Full marks2/2

The operating system copies the program and its data from secondary storage into main memory so that the CPU can fetch and execute its instructions.

Why: Copying the program and data into main memory (1) linked to the CPU fetching/executing instructions (1).

Some marks1/2

The operating system loads the program into main memory.

Why: The program is copied/loaded into main memory (1), but there is no linked development of how or what this leads to, so only one mark is given.

No marks0/2

The CPU fetches the program's instructions from main memory and executes them one at a time.

Why: This describes the fetch-decode-execute cycle, not the operating system loading or allocating memory, which is the Do not accept line; no creditworthy point is made.

3Calculate2 marksBinary Shifts Swap Remove

Computers manipulate binary patterns.

Complete the table with the result of applying the shift to the binary pattern.

[2 marks]
Binary patternShift8-bit binary result
1000 0001Logical shift right by 1
Mark scheme

Award one mark for each correct nibble in the correct order:

  • 0100 (1)
  • 0000 (1)

0 marks if the response is not 8-bit binary.

Example answers and how they were marked
Full marks2/2

0100 0000

Why: Every bit moves 1 place right, with 0s in from the left: both nibbles are correct (2).

Some marks1/2

0100 0001

Why: A slip in the last bit. The first nibble is correct (1); the second is not.

No marks0/2

0000 0010

Why: Shifts the bits the wrong way. Neither nibble is correct.

4Discuss6 marksTranslators Swap Remove

A student is writing a program in a high-level language. The student runs the program after every small change to check that it works.

Discuss whether the student should use an interpreter or a compiler while writing and testing the program.

Your answer should include:

  • how each translator deals with a syntax error
  • how much of the program is translated at a time
  • how this affects the student's testing.
[6 marks]
Mark scheme

Indicative content

How each translator deals with a syntax error

  • An interpreter stops as soon as it finds a syntax error and displays an error message.
  • With an interpreter, the lines before the error have already been executed, so the student can see how far the program got before it stopped.
  • A compiler reports errors at the end of translation, so the student gets a list of all the syntax errors in the program in one go.

How much of the program is translated at a time

  • An interpreter translates one line at a time and executes each line immediately.
  • A compiler translates the whole program in one go before any of it is run.
  • A compiler produces object code, so after every change the whole program must be compiled again before the student can run it.
  • An interpreter produces no object code, so the student does not have to wait for the whole program to be translated before it runs.

How this affects the student's testing

  • An interpreter suits this student because the program can be run straight away after each small change.
  • The interpreter stops at the first error found, so the student fixes that error and runs the program again, but may only find the next error on the next run.
  • Reporting every error at the end of compilation means the student can fix several errors at once, but cannot run the program until the whole program compiles.
  • The student should use an interpreter while testing, and compile the finished program once it works.

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)

Level 3 responses must relate the way each translator works to the student's testing, not just describe the two translators.

Do not accept answers about run-time or logic errors where no comparison of the translators is made.

Example answers and how they were marked
Full marks6/6

The student should use an interpreter while testing. An interpreter translates one line at a time and executes each line straight away, so as soon as the student has made a small change the program can be run without waiting for the whole program to be translated. If there is a syntax error, the interpreter stops at that line and displays an error message, and the lines before it have already been executed, so the student knows exactly where the problem is. A compiler translates the whole program in one go and only reports the errors at the end, so the student would get a list of all the syntax errors, but could not run any of the program until the whole program compiled successfully.

Why: Explains how each translator deals with a syntax error, how much is translated at a time (one line executed immediately against the whole program at once) and links both to the student's testing, with a conclusion. Level 3.

Some marks4/6

An interpreter translates one line at a time and stops when it finds an error, so the student can see where the error is. A compiler translates the whole program and reports all the errors at the end. The interpreter is better for testing because the student can run the program straight away after a change.

Why: Adequate: correct points about error reporting and one line at a time, with a recommendation, but the effect on testing is only asserted rather than reasoned through, so the linkage is not sustained. Level 2.

Some marks1/6

The student should use a compiler because it translates the program one line at a time and stops at the first error, which makes testing quicker.

Why: The roles of the two translators are reversed, so the answer only makes a basic point about testing more quickly. Level 1.

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

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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

Build a paper on this topic 18
Data Protection Act 14 questions Impact of AI 4 questions

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