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2.3.1Units and file size calculations

Edexcel GCSE Computer Science (1CP2) · Data › Data storage and compression

Practise Units and file size calculations. 11 exam-style questions plus unlimited generated ones on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.

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Quick recall

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State the number of bits in a nibble.
4
Write these units in order of size, starting with the smallest.
gibibyte   byte   tebibyte   mebibyte   kibibyte   nibble
nibble, byte, kibibyte, mebibyte, gibibyte, tebibyte
Convert 3 bytes into bits.
24

Sample questions

Written for this site in the style of Edexcel exam questions. They are not taken from real past papers.

Question 1Easy3 marks
(a) Identify the smallest unit of data.[1]
  • Byte
  • Nibble
  • Kibibyte
  • Bit
(b) State the number of bits in a nibble.[1]
(c) State the number of bytes in one kibibyte (KiB).[1]
Show the answer and mark scheme
(a) Answer: Bit
(b) Answer: 4
  • 4
(c) Answer: 1024
  • 1024
Question 2Medium4 marks
A student's project folder contains:
  • a report of 768 KiB
  • 12 photos of 2.5 MiB each
  • a video of 1.25 GiB
(a) Calculate the total size of the folder in MiB. Show your working.[3]
(b) State whether the folder will fit on an empty 1 GiB USB flash drive. Give a reason for your answer.[1]
Show the answer and mark scheme
(a) Answer: 1310.75 MiB
  • report: 768 ÷ 1024 = 0.75 MiB
  • photos: 12 × 2.5 = 30 MiB and video: 1.25 × 1024 = 1280 MiB
  • total: 1310.75 (MiB)
(b) Answer: No: 1310.75 MiB > 1024 MiB (the video alone is 1.25 GiB).
  • no, because 1310.75 MiB is more than 1 GiB (1024 MiB) / the video alone is larger than 1 GiB
Question 3Hard4 marks
A hard disk drive is sold as '2 TB'. The manufacturer uses 1 TB = 1,000,000,000,000 bytes.
(a) Construct an expression to calculate the capacity of the drive in tebibytes (TiB).
You do not need to do the calculation.[2]
(b) The value of the expression is about 1.82. Explain why a computer's operating system may report the capacity of this drive as less than 2.[2]
Show the answer and mark scheme
(a) Answer: 2,000,000,000,000 ÷ (1024 × 1024 × 1024 × 1024)
  • 2,000,000,000,000 / 2 × 10004 (bytes)
  • ÷ 10244 / ÷ (1024 × 1024 × 1024 × 1024)
(b) Answer: The label uses 1 TB = 1012 bytes; the OS counts in TiB (10244 bytes), which are bigger units, so it shows about 1.82.
  • the manufacturer uses decimal multiples (1 TB = 1012 bytes) but the operating system reports the size in binary multiples (1 TiB = 10244 bytes)
  • a tebibyte is larger than a terabyte, so the same number of bytes is a smaller number of TiB (about 1.82)

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