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Edexcel GCSE Computer Science (1CP2) Exam Questions

Build a practice paper from 631 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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5 questions · 7 marks

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1Multiple choice1 markCompression Swap Remove

Identify the definition of lossy compression.

[1 mark]
  • AData is removed only while the file is being transmitted
  • BData is permanently removed to reduce the file size
  • CData is restored exactly when it is decompressed
  • DData is stored using a dictionary of repeated patterns
Mark scheme
  • B Data is permanently removed to reduce the file size (1)
  • The only correct answer is B. The correct answer is data is permanently removed to reduce the file size.
  • A is not correct because the data removed by a lossy algorithm is not restored after transmission
  • C is not correct because that describes lossless compression, where the original file is rebuilt exactly
  • D is not correct because dictionary encoding is a lossless method that records repeated patterns once
Example answers and how they were marked
Full marks1/1

B Data is permanently removed to reduce the file size

Why: Correct option (1).

No marks0/1

C Data is restored exactly when it is decompressed

Why: Near miss: this describes lossless compression, so no mark.

No marks0/1

A Data is removed only while the file is being transmitted

Why: Misconception that compression only applies during transmission; the data is removed permanently, so no mark.

2Multiple choice1 markUnits & Conversion Swap Remove

A computer stores data in binary.

Identify the number of bits in one kibibyte.

[1 mark]
  • A1024
  • B8000
  • C8192
  • D8 388 608
Mark scheme
  • C 8192 (1)
  • The only correct answer is C. The correct answer is 8192.
  • A is not correct because 1024 is the number of bytes in a kibibyte
  • B is not correct because 8000 is the number of bits in 1000 bytes
  • D is not correct because 8 388 608 is the number of bits in a mebibyte
Example answers and how they were marked
Full marks1/1

C 8192

Why: Correct: one kibibyte is 1024 bytes and 1024 × 8 = 8192 bits (1).

No marks0/1

A 1024

Why: Near miss: 1024 is the number of bytes in a kibibyte, not the number of bits (0).

No marks0/1

B 8000

Why: Typical misconception: uses 1000 bytes for a kibibyte, giving 1000 × 8 = 8000 bits (0).

3Short recall1 markCompression Swap Remove

A company backs up its files to an external hard drive.

Give one reason why the company compresses the files before backing them up.

[1 mark]
Mark scheme

Award one mark for any of the following:

  • More files/data can be stored (in the same storage space) (1)
  • The files take up less storage space (1)
  • The backup is quicker/faster to complete (1)
  • Less data needs to be transferred to the backup device (1)

Do not accept 'makes the files more secure' or 'encrypts the files'.

Example answers and how they were marked
Full marks1/1

The compressed files take up less storage space, so more files can be backed up.

Why: The files take up less storage space (1).

No marks0/1

It reduces the amount of disk fragmentation.

Why: Near-miss: compression does not reduce disk fragmentation.

No marks0/1

It encrypts the files so they are safer if the drive is stolen.

Why: Misconception: compression does not encrypt files, and security is not accepted.

4Short recall2 marksUnits & Conversion Swap Remove

A solid state drive has a capacity of 5 gibibytes.

Give an expression to calculate the number of bits in 5 gibibytes. You do not need to do the calculation.

[2 marks]
Mark scheme

Award one mark for each of:

  • 5 × 1024^3 / 5 × 1024 × 1024 × 1024 / 5 × 2^30, for the number of bytes (1)
  • A fully correct expression with × 8 to convert bytes to bits, in any order, e.g. 5 × 1024^3 × 8, 8 × 5 × 2^30 (1)

Accept 5 × 1 073 741 824 × 8.

Accept 5 × 2^33 or 42 949 672 960 as a fully correct expression (2 marks).

Do not accept 5 × 1000^3 × 8, which uses decimal multiples.

Do not accept ÷ 8, which converts bits to bytes.

Example answers and how they were marked
Full marks2/2

8 × 5 × 2^30

Why: 5 × 2^30 is the number of bytes (1) and × 8 converts bytes to bits (1).

Some marks1/2

5 × 2^30

Why: Correct number of bytes using the binary multiple 2^30 (1), but no conversion to bits.

No marks0/2

5 × 1000^3 × 8

Why: Uses decimal 1000^3 instead of binary 1024^3, so the expression is not fully correct; no creditworthy point.

5Explain2 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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