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Edexcel GCSE Computer Science (1CP2) Exam Questions

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2 questions · 4 marks

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1Describe2 marksCompression Swap Remove

Data can be compressed using lossy or lossless compression.

Describe one difference between lossy compression and lossless compression.

[2 marks]
Mark scheme

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

  • Lossy compression permanently removes/discards some of the data (1) whereas lossless compression keeps all of the original data so the file can be restored/rebuilt exactly (1)
  • Lossy compression cannot reproduce/recreate the original file exactly (1) whereas lossless compression can decompress the file back to its original form (1)
  • Lossy compression can make a file smaller than lossless compression (1) because more of the original data is removed/discarded (1)
  • Lossy compression is used for images/sound/video (1) whereas lossless compression is used where all the original data must be kept, such as program files (1)

Allow one mark for a correct statement about one type of compression only, e.g. 'lossy compression permanently removes some data', with no comparison or development.

Do not accept 'lossy compression loses quality' on its own unless it states that data/information is removed or lost permanently.

Do not accept 'lossy is better' or 'lossless is safer' with no described difference.

Do not award a smaller file size on its own; it must be linked to data being removed or to no data being lost.

Example answers and how they were marked
Full marks2/2

Lossy compression permanently removes some of the data, whereas lossless compression keeps all of the original data so the file can be restored exactly.

Why: Linked difference: lossy permanently removes data (1) and lossless keeps all data so the file is restored exactly (1).

Some marks1/2

Lossy compression permanently removes some of the data.

Why: A correct statement about one type only (1), with no comparison to lossless or development, so the second mark is not earned.

No marks0/2

Lossless compression removes the data that is not needed so the file is smaller, but lossy compression keeps every bit of the data.

Why: The two types are the wrong way round; no creditworthy point, so no marks.

2Explain2 marksUnits & Conversion Swap Remove

A server stores a large amount of data.

The capacity of the server is 16 TiB. Explain one benefit of giving the capacity in tebibytes rather than in bytes.

[2 marks]
Mark scheme

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

  • The capacity is easier to read/write (1) because a tebibyte is 1024^4 bytes so the same capacity in bytes would have many more digits (1)
  • The number is shorter (1) because writing 16 TiB instead of 17 592 186 044 416 bytes uses far fewer digits (1)
  • There is less chance of making a mistake when copying the value (1) because a long byte count of many digits is easy to mistype (1)

For both marks, the expansion must follow/associate with the statement and must refer to the number of digits/length of the value.

Allow 'fewer digits'/'shorter number'/'less chance of error' on its own for the first mark; the second mark needs the linked reason that a tebibyte is 1024^4 bytes, so the value in bytes would be very long/have many more digits.

Do not accept 'it is bigger'/'tebibytes are larger' on its own, as this does not give a benefit of using them.

Do not accept 'easier' on its own without saying what is easier, e.g. fewer digits/shorter number.

Do not accept 'because tebibytes are used for large storage' without a reason about the number of digits/readability.

Example answers and how they were marked
Full marks2/2

It is easier to read because 16 TiB has fewer digits than the same capacity written in bytes, which would be a very long number.

Why: Point that the number is easier to read (1); linked reason that the byte count would have many more digits (1).

Some marks1/2

It uses fewer digits.

Why: States the benefit of fewer digits (1); no linked reason about a tebibyte being 1024^4 bytes so the byte count is very long (0).

No marks0/2

Because a tebibyte is bigger than a byte.

Why: States a fact about the unit, which the mark scheme does not accept on its own; no point about fewer digits or readability, so no mark.

Questions by topic

2.1 Binary

Build a paper on this topic 58
Adding Binary Numbers 6 questions Binary and Hexadecimal Basics 10 questions Binary Shifts 6 questions Binary to Denary Conversion 6 questions Binary to Hexadecimal Conversion 6 questions Denary to Binary Conversion 6 questions Denary to Hexadecimal Conversion 6 questions Denary to Negative Binary Conversion 6 questions Hexadecimal to Binary Conversion 6 questions

2.2 Data representation

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Character Sets 18 questions Images 19 questions Sound 19 questions

2.3 Data storage and compression

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Compression 18 questions Units & Conversion 6 questions

3.1 Hardware

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Embedded Systems 17 questions Fetch Decode Execute Cycle 15 questions Primary Memory 15 questions Secondary Memory 15 questions Stored Program Computers 15 questions

3.2 Software

Build a paper on this topic 124
File Management 18 questions Memory Management 16 questions Peripheral Management 11 questions Process Management 12 questions Purpose & Function of Operating Systems 17 questions Software Basics 13 questions User Management 18 questions Utility Software 19 questions

3.3 Programming languages

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Low and High Level Languages 19 questions Translators 18 questions

4.1 Networks

Build a paper on this topic 138
Addressing 16 questions LANs & WANs 16 questions Network Speed 5 questions Packet Switching 16 questions Protocols & Layers 17 questions The Internet 16 questions Topologies 17 questions Wired Connections 17 questions Wireless Connections 18 questions

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