A-LevelComputer ScienceData representation9618/12 · Oct/Nov 2023 · Q36 Marks

State one difference between a kibibyte and a megabyte.

(a)State one difference between a kibibyte and a megabyte.[1]
(b)(i)Convert the denary value into a 12-bit two's complement binary integer. -196 Answer[1]
(b)(ii)Convert the Binary Coded Decimal (BCD) into denary. 100001100101 Answer[1]
(b)(iii)Convert the unsigned binary integer into denary. 000111010110 Answer[1]
(c)Identify one practical application of BCD and justify why BCD is used in this application. Application Justification[2]

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2023). The mark or mark type is shown in brackets.

[1] (a) Either: kibibyte = 1,024 bytes // 2^10 bytes and megabyte = 1000 kilobytes // 1 000 000 bytes // 10^3 kilobytes // 10^6 bytes. Or: kibi is binary prefix and mega is denary prefix.
[1] (b)(i) 1111 0011 1100
[1] (b)(ii) 865
[1] (b)(iii) 470
[2] (c) Application: An application that performs financial / banking calculations. Justification: because it is difficult to represent decimal values exactly in normal binary and financial transactions use only two decimal places and must be accurate, no accumulating errors. OR Application: Electronic displays, e.g. calculators, digital clocks. Justification: because visual displays only need to show individual digits and conversion between denary and BCD is easier. OR Application: The storage of the date and time in the BIOS of a PC. Justification: because conversion with denary is easier.

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