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Edexcel GCSE Computer Science (1CP2) Exam Questions

Build a practice paper from 604 exam-style questions, each with its mark scheme and example answers. Print it, or answer it on paper and then open the mark schemes. Or browse the questions by topic.

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4 questions · 6 marks

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1Multiple choice1 markStored Program Computers Swap Remove

Identify the function of the control unit in the fetch-decode-execute cycle.

[1 mark]
  • ADecodes instructions
  • BPerforms arithmetic operations
  • CStores data and instructions
  • DTemporarily stores data being processed
Mark scheme
  • A Decodes instructions (1)
  • The only correct answer is A. The correct answer is Decodes instructions.
  • B is not correct because the arithmetic logic unit performs arithmetic operations
  • C is not correct because main memory stores data and instructions
  • D is not correct because registers temporarily store data being processed
Example answers and how they were marked
Full marks1/1

A Decodes instructions

Why: Correct option: the control unit decodes instructions during the fetch-decode-execute cycle (1).

No marks0/1

C Stores data and instructions

Why: Main memory stores data and instructions, not the control unit; this is a common distractor, so no mark.

No marks0/1

B Performs arithmetic operations

Why: Arithmetic operations are performed by the ALU, not the control unit; a common confusion between CPU components, so no mark.

2Multiple choice1 markCharacter Sets Swap Remove

ASCII is a character set used for representing text.

Identify the number of bits used to encode each character in ASCII.

[1 mark]
  • A6
  • B7
  • C8
  • D16
Mark scheme
  • B 7 (1)
  • The only correct answer is B. The correct answer is 7 bits.
  • A is not correct because 6 bits give only 64 different characters
  • C is not correct because 8 bits are used by extended ASCII to give 256 characters
  • D is not correct because 16 bits give 65 536 different characters, which is far more than the 128 in ASCII
Example answers and how they were marked
Full marks1/1

B 7

Why: B is the only correct answer: each ASCII character is encoded using 7 bits (1).

No marks0/1

C 8

Why: Near miss scoring 0: 8 bits is extended ASCII, and the scheme's C line says extended ASCII, not ASCII, is not the answer.

No marks0/1

A 6

Why: Misconception scoring 0: 6 bits give only 64 different characters, so it cannot be ASCII.

3Describe2 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.

4Describe2 marksTranslators Swap Remove

A high-level program must be translated into machine code before it can be run.

Describe how a compiler and an interpreter differ in when the translated code is executed.

[2 marks]
Mark scheme

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

  • The interpreter executes each line as soon as it has been translated (1) so translation and execution happen together/at the same time (1)
  • The compiler translates the whole program first (1) and the machine code is run later/separately (1)
  • The interpreter translates the code and runs it while the program is running (1) whereas the compiler does not run the code it produces (1)
  • The compiler produces translated code that is executed only after all the translation has finished (1) but the interpreter executes each line immediately (1)

Allow 'translates one line at a time' where it is linked to executing each line immediately.

Do not accept answers that only state that a compiler is faster/an interpreter is slower, without reference to when execution happens.

Do not accept answers that only give object code, error reporting or portability, without reference to when execution happens.

Do not accept the compiler executing the program as it translates it.

Example answers and how they were marked
Full marks2/2

The compiler translates the code first and the program is executed afterwards, but the interpreter executes each line as soon as it has been translated.

Why: Compiler translates the whole program first and it is executed afterwards (1) and interpreter executes each line as soon as it is translated (1).

Some marks1/2

The interpreter executes each line immediately after translating it.

Why: Correct interpreter timing (1); no comparison with when the compiler's translated code is executed.

No marks0/2

The compiler executes the program line by line as it translates it.

Why: Reverses the two translators; a compiler does not execute the program it translates, so no mark.

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