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Edexcel GCSE Computer Science (1CP2) Exam Questions

Build a practice paper from 693 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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3 questions · 6 marks

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1Short recall2 marksUnits & Conversion Swap Remove

Data storage is measured in binary multiples.

Define the term bit.

[2 marks]
Mark scheme

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

  • A binary digit (1)
  • Has the value 0 or 1 (1)
  • The smallest unit of data storage (1)
  • A single 0 or 1 (1)

Allow binary digit/binary place value for binary digit

Allow a single binary digit for a single 0 or 1

Do not accept a group of 8 bits/half a nibble of 4 bits, which describe a byte or a nibble

Do not accept a binary number/binary on its own

Example answers and how they were marked
Full marks2/2

A binary digit that can have the value 0 or 1.

Why: A binary digit (1) and has the value 0 or 1 (1).

Some marks1/2

It is the smallest unit of data storage.

Why: Smallest unit of data storage (1), but does not state that it is a binary digit or that it has the value 0 or 1.

No marks0/2

A group of 8 bits.

Why: Describes a byte, not a bit; no creditworthy point and named in the Do not accept line.

2Describe2 marksCompression Swap Remove

Photographs are often saved as JPG files.

Describe how lossy compression reduces the size of a photograph.

[2 marks]
Mark scheme

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

  • Some data is removed permanently (1) choosing detail that people are least likely to notice (1)
  • Small changes in colour/shade are discarded (1) so fewer different values need to be stored (1)
  • Similar pixels are stored as one value (1) so there are fewer values in the file (1)
  • Fine detail is removed (1) so fewer bits are needed to store each area (1)

Do not accept answers that say repeated patterns are stored once / no data is lost.

Example answers and how they were marked
Full marks2/2

It permanently removes some of the pixel data that the human eye is unlikely to notice, such as small colour changes.

Why: Linked point: data removed permanently (1) and development: detail least noticeable (1).

Some marks1/2

Some of the data in the photograph is removed permanently.

Why: States permanent removal of data (1); no linked development is given (1).

No marks0/2

It finds repeated pixels and stores them once, so no data is lost.

Why: Describes lossless compression, not lossy; no credit.

3Explain2 marksCompression Swap Remove

Files can be compressed using lossy or lossless compression.

Explain one difference between lossy compression and lossless compression.

[2 marks]
Mark scheme

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

  • Lossy compression permanently removes some data (1) whereas lossless compression does not remove any data (1)
  • With lossy compression the original file cannot be recreated exactly (1) but with lossless compression it can (1)
  • Lossy compression can produce a smaller file/a higher compression ratio (1) whereas lossless compression keeps all of the data so compresses less (1)

For both marks, the expansion must follow/associate with the statement.

Allow 'removes data' for 'permanently removes data'.

A correct statement about only one type of compression, with no contrast, earns one mark.

Do not accept a reversed statement such as 'lossless compression loses data and lossy compression does not'.

Do not accept 'lossy makes the file smaller' on its own, because lossless compression also reduces the file size; the answer must say that data is removed.

Do not accept 'lossy is worse quality' on its own without saying data is removed.

Example answers and how they were marked
Full marks2/2

Lossy compression removes some data permanently, but lossless compression keeps all of the data.

Why: Lossy removes data permanently (1) and contrasts with lossless keeping all data (1).

Some marks1/2

Lossy compression removes some of the data.

Why: A correct statement about one type of compression with no contrast earns one mark (1); no contrasting statement about lossless compression is given.

No marks0/2

Lossless compression removes data so the file is smaller, but lossy compression keeps all the data.

Why: Reversed statement: lossless keeps all the data and lossy removes it, so no mark is awarded.

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