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Edexcel GCSE Computer Science (1CP2) Exam Questions

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4 questions · 11 marks

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1Multiple choice1 markCharacter Sets Swap Remove

Characters are encoded using 7-bit ASCII.

Identify the number of different characters that can be represented using 7-bit ASCII.

[1 mark]
  • A64
  • B127
  • C128
  • D256
Mark scheme
  • C 128 (1)
  • The only correct answer is C. The correct answer is 128.
  • A is not correct because 6 bits give only 64 different combinations
  • B is not correct because 127 is the largest 7-bit value, not the number of characters that 7 bits can represent
  • D is not correct because 256 characters need 8 bits, as used by 8-bit extended ASCII
Example answers and how they were marked
Full marks1/1

C 128

Why: Selects the only correct option (1): 7 bits give 2 to the power of 7, which is 128 different characters.

No marks0/1

D 256

Why: Near miss scoring 0: 256 is the number of characters that 8 bits give in extended ASCII, not 7-bit ASCII.

No marks0/1

B 127

Why: Misconception scoring 0, the off-by-one error the examiners' report describes: 127 is the largest 7-bit value, but 7 bits give 128 different characters.

2Short recall2 marksStored Program Computers Swap Remove

Computers use the von Neumann stored program concept.

Define the term stored program concept.

[2 marks]
Mark scheme

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

  • Program instructions are stored in main memory/RAM (1)
  • The data used by the program is stored in main memory/RAM (1)
  • The CPU fetches/reads instructions from main memory to execute them (1)
  • The program can be run without the instructions being input again (1)

Allow 'the program is stored in memory' for one mark.

Do not accept answers about programs being stored on secondary storage, such as a hard disk or USB memory stick.

Do not accept answers that only describe the von Neumann architecture (e.g. having a CPU and memory) without stating that instructions are stored in main memory.

Example answers and how they were marked
Full marks2/2

Both the program instructions and the data the program uses are held in the same main memory, and the CPU fetches these instructions from memory to execute them.

Why: Instructions stored in main memory (1) and the CPU fetches instructions from memory to execute them (1).

Some marks1/2

Program instructions are stored in main memory.

Why: Instructions stored in main memory (1). No second point about data being stored in the same memory or about the CPU fetching instructions.

No marks0/2

The program is saved on the hard disk so that it can be loaded into RAM when the user runs it.

Why: A near-miss about secondary storage, which the mark scheme says not to accept; the stored program concept is about instructions being held in main memory.

3Short recall2 marksCompression Swap Remove

Images and sound can be stored using lossy compression.

Define the term lossy compression.

[2 marks]
Mark scheme

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

  • Reduces the size of a file (1)
  • Permanently removes/loses some data (1)
  • The original file cannot be recreated/restored exactly (1)

Allow 'some data is deleted/discarded and cannot be recovered' for the second mark.

Do not award the first mark where the response also states that no data is lost.

Do not accept 'removes repeated data' (this describes lossless compression).

Example answers and how they were marked
Full marks2/2

Lossy compression reduces the size of a file by permanently removing some data, so the original cannot be restored exactly.

Why: Reduces the size of a file (1); permanently removes some data (1); maximum two marks awarded.

Some marks1/2

It makes a file smaller.

Why: Reduces the size of a file (1); no reference to data being permanently lost.

No marks0/2

It makes a file smaller without losing any of the data.

Why: States that no data is lost, which describes lossless compression; the first mark is not awarded.

4Discuss6 marksUtility Software Swap Remove

A small graphic design company keeps all of its project files on one desktop computer. The computer's hard disk has failed and some files have been lost. The owner has been told to use backup software.

Discuss the backup strategy the company should use.

Your answer should include:

  • the types of backup that could be used
  • where and how often backups should be made
  • how the backups would be used if the hard disk failed again.
[6 marks]
Mark scheme

Indicative content

Types of backup that could be used

  • A full backup copies all of the company's project files every time it is run, so the whole set of files is held together in one backup.
  • A full backup takes longer to make and needs more storage space than an incremental backup.
  • An incremental backup copies only the files that have changed since the previous backup, so it is quicker to run each evening.
  • Restoring from incremental backups needs the last full backup plus every incremental backup made since, which takes longer and is more complex.
  • A weekly full backup with nightly incremental backups can be suitable for the company when the reason is explained using the properties of the two types.

Where and how often backups should be made

  • Backups should be kept on a separate device and, ideally, at a different location, so that a fire or theft in the office cannot destroy the computer and the backups together.
  • Backups should be made regularly, for example every evening, so that at most one day's design work would be lost.
  • Cloud storage can hold copies off-site automatically, without the owner taking a disk home.
  • An external hard disk or USB flash drive can be used as the backup medium, with a copy kept away from the office.

How the backups would be used if the hard disk failed again

  • If the hard disk fails again, the backup software is used to restore the latest full backup and any later incremental backups onto a replacement disk.
  • The restored project files allow the company to carry on working and meet its clients' deadlines.
  • The backups should be tested by restoring a file so that the company knows the backup is usable before it is needed.
  • Backup software does not repair the failed hard disk itself, so a replacement disk is still needed.

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 requires all three bullets to be developed and applied, including both types of backup (or a justified combination) and a restoration sequence; a response that describes only a full backup cannot reach Level 3.

An answer that explains only one type of backup with at most a brief location or frequency point and no developed restoration is Level 1 (1–2 marks). Credit one off-site point only: cloud storage, an external disk kept elsewhere and 'a different location' are the same point. Do not accept that backup software repairs a failed hard disk or recovers files that were never backed up; an answer that only makes this claim is Level 0. An unsupported weekly-full/nightly-incremental recommendation is not credited.

Example answers and how they were marked
Full marks6/6

The company should make a full backup once a week and incremental backups every evening. A full backup copies every project file, so the whole set is held in one place, but it takes a long time and a lot of space. An incremental backup copies only the files that have changed since the last backup, so it is quick enough to run each night. The backups should be copied to an external hard disk that the owner takes home, or uploaded to cloud storage, so that a fire or a theft cannot destroy the computer and the backups together. Backing up every evening means that at most one day's design work would be lost. If the hard disk fails again, the backup software is used to restore the latest full backup and then each incremental backup onto a new disk, so the company can carry on meeting its clients' deadlines.

Why: Level 3: full and incremental backups are explained and applied to a weekly and nightly schedule (AO1); off-site storage and the restore sequence onto a replacement disk are developed and clearly tied to the hard disk failure (AO2).

Some marks2/6

The company should back up its files to an external hard disk. A full backup copies all of the files, so the project files can be restored if the hard disk fails again. The backup should be kept in a different room in case there is a fire.

Why: Level 1: names a full backup and briefly links it to restoring files, and gives a weak location point, but there is no incremental backup, frequency or developed restore sequence, so the points remain basic and independent.

No marks0/6

Backup software repairs the hard disk when it fails, so the company will not lose anything and can open the files again.

Why: Level 0: the only claim is that backup software repairs the failed hard disk and prevents all loss, which the mark scheme does not accept; no valid type, location, frequency or restoration point is made.

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