O-LevelComputer ScienceData Representation2210/13 · Oct/Nov 2024 · Q115 Marks

Data can be measured using different units of storage.

(a)Tick (✔) one box to show which of the following is the largest unit of data storage. A tebibyte (TiB) B pebibyte (PiB) C mebibyte (MiB) D gibibyte (GiB)[1]
(b)A computer has primary storage. Give one example of primary storage. Explain the purpose of your chosen example. Example Explanation[3]
(c)(i)All data is converted to binary to be processed by a computer. Calculate the binary number for the denary number 175. Show all your working.[2]
(c)(ii)Give the binary number for the given hexadecimal numbers. 15 2D 091 Working space[3]
(d)Binary integers can be added together. Add the two binary integers using binary addition. Show all your working. Give your answer in binary. 11100011 +11001100[4]
(e)Calculate the denary number for the two's complement binary integer 10001110. Show all your working.[2]

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2024). The mark or mark type is shown in brackets.

[1] B
[3] One mark for correct example. Two marks for matching explanation. RAM: To store data/instruction that is currently in use; To store software/programs that are currently in use; For volatile storage // to store data temporarily; To allow data to be accessed directly by the CPU/processor // To allow data to be stored closer to the CPU/processor. ROM: To store the BIOS; To store the bootstrap/bootloader; To store start-up instructions; To store the firmware; For non-volatile storage // to store data permanently; To store data/instructions that should not change (unless needed). Cache: To store frequently used instructions/data; For volatile storage // to store data temporarily
[2] One mark for valid working, for example: 128 + 32 +8+4+2+1; One mark for correct answer: 10101111
[3] 0001 0101; 0010 1101; 0000 1001 0001
[4] One mark for each correct nibble; One mark for method of working, for example: carries; One mark for identification of overflow. Addition: 11100011 + 11001100 = 110101111
[2] One mark for correct working, for example: flip and add; One mark for correct denary: -114

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