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Edexcel GCSE Computer Science (1CP2) Exam Questions

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3 questions · 9 marks

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1Multiple 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.

2Describe2 marksTranslators Swap Remove

Source code can contain syntax errors.

Describe how a compiler and an interpreter differ in the way they deal with syntax errors.

[2 marks]
Mark scheme

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

  • The compiler reports all syntax errors after translation has finished (1) whereas the interpreter stops at the first error it finds (1)
  • The interpreter reports a syntax error as soon as it finds one (1) and does not translate/execute any more of the program (1)
  • The compiler continues translating after an error (1) and reports the errors at the end (1)
  • The interpreter stops translating when it reaches an error (1) but the compiler finishes translating before reporting errors (1)

Do not accept answers about fixing/correcting errors or about object code.

Do not award 'the compiler finds more errors' without saying errors are reported at the end.

Example answers and how they were marked
Full marks2/2

A compiler reports all the syntax errors at the end of translation, whereas an interpreter stops and reports the error as soon as it finds one.

Why: Compiler reports errors at the end (1) and interpreter stops/reports at the first error (1).

Some marks1/2

An interpreter stops translating when it finds a syntax error.

Why: Interpreter stops at the first error (1); no comparison with when the compiler reports errors.

No marks0/2

A compiler reports a syntax error immediately, before translating the rest of the program.

Why: Reverses the compiler's behaviour; it finishes translating before reporting errors.

3Discuss6 marksFile Management Swap Remove

A small business has one computer with a single hard disk. Two employees save documents and photographs to it every day. The operating system manages the disk.

Discuss why the operating system needs to manage where files are stored on the disk.

Your answer should include:

  • how the operating system allocates disk space when a file is saved
  • how the operating system keeps track of each file
  • what could happen if the operating system did not manage files
[6 marks]
Mark scheme

Indicative content

Allocating space

  • The operating system checks that there is enough free space before a file is saved, so a large photograph does not make the save fail.
  • The operating system finds free space on the disk and allocates it to the new file, so the file's data has somewhere to be written.
  • Disk space is allocated so that a file is not written on top of data that already belongs to another file.
  • When a file is deleted, the operating system marks its space as free so it can be used again by the next document that is saved.

Keeping track

  • The operating system keeps a record of the name, size and location of every file, so it knows where each file is stored.
  • The record is updated whenever a file is saved, renamed or deleted, so it still matches what is on the disk.
  • The operating system uses this record to find a file again, so an employee can open a document or photograph that was saved earlier.
  • The record lets the operating system tell the two employees' documents and photographs apart, even though they are all on the same disk.

Without this management

  • Two files could be given the same space, so one document would overwrite another and the work would be lost.
  • The operating system would not know where a file is stored, so a saved document could not be found and opened again.
  • Space used by deleted files might never be freed, so the disk would fill up and new files could not be saved.

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 cover both the allocation of space and the tracking of files, with at least one consequence of no management linked to its cause. Reference to a file being split across blocks that are not next to each other, or to the record holding the location of each block, is Level 3 detail and is not required.

Basic, unlinked points with no application to the business's documents or photographs, and a consequence such as 'files would be lost' with no cause given, are limited to Level 1; to reach Level 2 a point must be linked to a reason (for example, the record is kept so a document can be found again) and be applied to the context. Do not accept defragmentation, process scheduling, user management, peripheral management, or backup and antivirus scanning, as file management.

Example answers and how they were marked
Full marks6/6

Before a document is saved, the operating system checks that there is enough free space on the single disk, so a large photograph cannot make the save fail. It then finds free space and allocates it to the new file, making sure it does not write over data that already belongs to another file. The operating system keeps a record of the name, size and location of every file and updates it whenever a file is saved or deleted. It uses this record to find a file again, so an employee can open a document that was saved earlier. Without this, the two employees could be given the same space, so one document would overwrite the other, or the operating system would not know where a file is stored and the business could not find its work again.

Why: Covers both allocation (free space check, free space given to the file, no overwriting) and tracking (record of name, size and location, updated on save, used to find the file), applies it to the business's single disk and its two employees' documents and photographs, and links the consequences of no management to their causes: Level 3.

Some marks2/6

The operating system decides where on the disk a file is saved. It also keeps a record of where each file is stored. Without this, files would be lost.

Why: Two basic points are made: space is allocated when a file is saved, and a record of where each file is stored is kept. Neither is linked to a reason, there is no application to the business's documents and photographs, and 'files would be lost' is given with no cause: Level 1, top of the level.

Some marks1/6

The operating system puts files in the right place so the disk does not get full. It also defragments the disk to make the files smaller.

Why: One basic point about the operating system placing files on the disk so it does not fill up (Level 1). Defragmentation is not file management and does not make files smaller, so it is not credited: Level 1.

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