2022 ACSBR Computing P1 Solutions

Anglo-Chinese School (Barker Road) Preliminary Examination 2022 16 Secondary 4 Express Computing 7155/01 Anglo-Chinese School (Barker Road) PRELIMINARY EXAMINATION 2022 SECONDARY FOUR EXPRESS COMPUTING PAPER 1 ANSWER KEY

Anglo-Chinese School (Barker Road) Preliminary Examination 2022 17 Secondary 4 Express Computing 7155/01 1 The diagram show four types of computer or network identifiers and eight examples that they could be represented on the right. Draw one line between each identifier to its correct representation. Identifiers Example of Representation • 2001:db8::20:17:bad:c0de • 55 IPv4 • • H4-7G-09-E0-D2-5Z (invalid due to G and Z characters) MAC • • 129.126.67.97 Port number • • 3A (invalid as port number is only denary) IPv6 • • 108.F5.153.AF (invalid as IPv4 only has denary numbers) • F4-7B-09-E0-D3-54 • 2010:db8::20::b2d:134 (invalid as IPv6 should have no more than one set of double colons) [4]

Anglo-Chinese School (Barker Road) Preliminary Examination 2022 18 Secondary 4 Express Computing 7155/01 2 (a) Convert the binary number 101 1011 into a denary and hexadecimal number. Denary: 91 Hexadecimal: 5B [2] (d) Convert the denary number 1698 into hexadecimal number. Show your working. Divide by 16 1698 2 2 106 10 A 6 6 6 0 6A2 [2] (e) Explain why hexadecimal numbers are commonly used to represent binary numbers. Hexadecimal format is quite compact and thus much easier to read/understand compared to the long binary strings of 1's and 0's No marks for single point of short/compact or easy to read [1]

Anglo-Chinese School (Barker Road) Preliminary Examination 2022 19 Secondary 4 Express Computing 7155/01 3 Computer memory is measured in terms of the number of bytes. (c) (i) Explain what is meant by the term byte? A byte is a unit of data made up of eight bits. [1] (ii) State the number of bytes in 5 mebibytes (MiB). 5 × 1024ଶ = 5,242,880 bytes [1] (d) (i) Optical and solid-state are two common types of storage media. Give two differences between these two types of storage media. 1 Data is stored as very small pits or indentations that can be read or written by a laser for optical media. For solid -state, data is stored in electronic circuits called “flash memory” that have no moving parts 2 Optical media are vulnerable to scratches and fingerprints while solid -state media are not as vulnerable to drops, mechanical shocks, scratches or fingerprints. [2] (ii) State another type of storage media. Magnetic [1] Cloud storage not accepted as cloud storage are also classified as magnetic or solid- state storage at server end. 4 Data collection is the first of four stages in the data life cycle. (a) Describe any two data collection activities. 1 Any of the two activities: performing int