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Edexcel GCSE Computer Science (1CP2) Exam Questions

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5 questions · 13 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

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.

3Short recall2 marksEmbedded Systems Swap Remove

A digital camera contains an embedded system.

Give two functions that the embedded system performs in the digital camera.

[2 marks]
Mark scheme

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

  • Focus the lens/autofocus (1)
  • Control the shutter (speed) (1)
  • Control the flash/decide when the flash is needed (1)
  • Measure the light level to set the exposure/the aperture (1)
  • Stabilise the lens/image stabilisation (1)
  • Zoom the lens in and out (1)
  • Detect a face/smile (1)

Do not accept 'take a photograph'/'take a picture'/'capture an image', as taking photographs is the function of the camera, which is given in the question.

Do not accept 'press the button' as this is an action of the user, not a function performed by the embedded system.

Do not accept vague answers such as 'use the camera', 'turn the camera on and off' or 'make the camera work', which do not name a function that the embedded system performs.

Example answers and how they were marked
Full marks2/2

It focuses the lens and decides when the flash should fire.

Why: Focus the lens (1) and control the flash (1).

Some marks1/2

It controls the zoom and takes a picture when the button is pressed.

Why: Zoom the lens credited (1); 'takes a picture' is not accepted because taking photographs is the function of the camera, which is given in the question, and 'press the button' is the user's action, not a function of the embedded system.

No marks0/2

It takes a picture when the button is pressed and it makes the camera work.

Why: No mark: 'takes a picture' repeats the camera's function given in the question, 'press the button' is an action of the user, and 'makes the camera work' is too vague to name a function.

4Calculate3 marksAdding Binary Numbers Swap Remove

Binary patterns can represent numbers.

(a)

Complete the table to show the 8-bit result of the binary addition.

[2 marks]
1286432168421
11011011
11011100
Mark scheme

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

  • 1011 (1)
  • 0111 (1)

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

Ignore a carry shown beyond the eighth bit.

Example answers and how they were marked
Full marks2/2

1011 0111

Why: 219 + 220 = 439, which needs 9 bits; the 8 bits that are kept are both correct (2).

Some marks1/2

0000 0111

Why: Forgets to carry the 1s. The second nibble is correct (1); the first is not.

No marks0/2

1101 1111

Why: Never carries. Neither nibble is correct.

(b)

State the name of the error that occurs when this addition is carried out.

[1 mark]
Mark scheme

Award one mark for:

  • overflow (error) (1)
Example answers and how they were marked
Full marks1/1

Overflow

Why: The result needs more bits than are available (1).

No marks0/1

Underflow

Why: A near miss: the result is too big for 8 bits, not too small.

No marks0/1

A syntax error

Why: A syntax error is a mistake in a program's code, not in arithmetic.

5Discuss6 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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