MSHS 2020 Computing P1 Solution

Class/ Index Number / Centre Number/ ‘O’ Level Index Number / Name MARIS STELLA HIGH SCHOOL PRELIMINARY EXAMINATIONS SECONDARY FOUR COMPUTING 7155 Paper 1 Written 26 August 2020 2 hours Candidates answer on the Question Paper No Additional Materials are required. SOLUTION For Examiner’s Use 80

2 This document consists of 14 printed pages. 1 Draw a line between the description and the correct spreadsheet function. Description Function CEILING Returns the kth largest number in range RAND Returns the largest number out of the numbers in the given range or cell references RANDBETWEEN Returns a random number greater than or equal to zero and less than one HLOOKUP Rounds up a number to an exact number of significance LARGE Search for data in a row and returns associated data in the same column. MAX [5] 2 (a) A sports event company uses a digital camera attached to a drone to video their events from the sky. The video is stored as it is captured, on a device that is attached to the drone. Circle the most suitable type of media to store the video. (i) Optical Magnetic Solid State [1] (ii) Give two reasons to justify your choice. Three from: • It has no moving parts so it will be durable as the drone moves/ able to withstand large impact/ less prone to data loss from shaking/impact • It is small/compact so it can easily fit onto the device • It is light so it will not be difficult to lift for the drone • It can hold a large amount of data needed for the video/film footage • Uses less power so drone battery will last longer • Solid state provides faster access/transfer of data than the other two [2] Comment: To earn each mark, state one characteristic of storage media + explain how this characteristic makes it suitable (1m) Unacceptable: Solid state is portable (characteristic stated) but no explanation provided.

3 3 Insert three of the following words about different types of software in the correct place in each scenario below. public domain software proprietary software open courseware shareware freeware (a) Ali’s company requires productivity software that can be used in his business for emailing customers, creating orders, and tracking of the company’s profits and losses. He would also like regular customer support and updates from the software company that owns the source code of the software. The most suitable category of software for this usage is proprietary software (b) Mingxuan wants to learn more about Python programming during the school holidays. He wants to enrol for free online lessons provided by a university’s website that contains videos and training materials for his learning. The most suitable category of software for this usage is open courseware (c) Sharon wants to purchase accounting software for her company’s use. She wants to try out a few features of the software before making a decision whether to purchase the full version. The most suitable category of software for this usage is shareware [3] 4 Five statements about interpreters and compilers are shown in the table below. Tick ( ü ) to show whether the statement refers to an interpreter or to a compiler. Statement Interpreter Compiler Translates the entire program in one go. √ Takes one statement at a time and executes it. √ Program runs at a faster speed because translation was completed earlier. √ Stops the translation process as soon as the first error is encountered. √ Syntax errors are detected before program runs. √ [5]

4 5 (a) Convert the positive whole denary number 388 into a 12-bit binary number. Divide (398)10 successively by 2 until the quotient is 0: 388 / 2 = 194 with 0 remainder 194 / 2 = 97 with 0 remainder 97 / 2 = 48 with 1 remainder 48 / 2 = 24 with 0 remainder 24 / 2 = 12 with 0 remainder 12 / 2 = 6 with 0 remainder 6 / 2 = 3 with 0 remainder 3 / 2 = 1 with 1 remainder 1 / 2 = 0 with 1 remainder 000110000100 [2] (b) Convert this binary pattern into hexadecimal. 1 0 1 1 0 0 1 0 1 0 0 1 0 1 1 0 B296 [4] (c) RGB codes are one example of where hexadecimal numbers are preferred to binary numbers. Give two reasons to explain so. • hexadecimal numbers are more compact than binary numbers/ the number of digits used to represent a given hexadecimal number is fewer than in binary • uses less storage than binary numbers / a small number of hex digits can represent more data • quick and easy to convert between hexadecimal numbers and binary • easier to identify values using hexadecimal • easier to spot errors using hexadecimal [2] (d) State another two ways in which hexadecimal numbers are used to represent data. • Colour codes / Colour in HTML / CSS • Error messages • Locations in memory • Memory dump / debugging • IPv6 address (Unacceptable: IP address, version not stated) • ASCII / Unicode • Assembly language • URL • M.A.C Addresses [2]

5 6 Complete the following paragraphs by filling in the missing words about networks. A local area network is a network of computing devices connected within a small geographical area, typically within the same building, such as in an office. A wide area network is a network of computing devices covering across multiple geographical locations, such as those between a main office in a country and branch offices in other countries. In an office, there would typically be many client/node computers that initiate connections to request for resources and services from a centralised computer to perform operations. This computer which fulfils these requests is known as a server as it centrally manages resources and services. This type of network is more secure/safe than a peer-to-peer network as access rights are centrally controlled. X efficient [5] 7 A program asks the user for a string and prints out the string in reverse order. For example, “Computing” returns a result of “gnitupmoC”. For each test case condition below, write down one expected input and one expected output. Test Case 1 for Normal Conditions Expected Input “Apple” Expected Output “elppA” Test Case 2 for Boundary Conditions Expected Input ““ Expected Output “” Test Case 3 for Erroneous Conditions Expected Input -50 / “-50” / [1,2,3] Expected Output Invalid input. A string is expected. Comments: No marks if student leaves out “” (normal conditions) No marks for single character (boundary conditions) Message should be meaningful on expected type required. (erroneous condition) [6]

6 8 Personal information needs to be kept safe from unauthorised access. Explain how the following industries verify personal information. For each industry, identify the authentication method and explain how it is implemented to verify user identity. (a) Online banking services by banks (i) Authentication Method: Two-factor authentication [1] (ii) How it is implemented: Any two: • Users are issued a security token/device for them to access online banking OR • User registers his phone/email address as a 2FA device. • There are two levels of authentication where user first confirms identity by providing a secret password or personal identification number (PIN) to the website • This is followed by a one-time password (OTP) generated from the security token or a mobile phone that the user owns, which has to be keyed into the website • OTP is single-use only/expires after a short duration [2] (b) Passport checking by Immigrations Department (i) Authentication Method: Biometrics [1] (ii) How it is implemented: Any two: • A user is identified though measuring a physical trait/characteristic • This characteristic is unique • Thumbprint or retina eye scan or facial recognition may be used • Data is