CWSS 2020 Computing P1 Solution

COMMONWEALTH SECONDARY SCHOOL PRELIMINARY EXAMINATION 2020 COMPUTING Paper 1 (Theory) Sec 4 E/4NA Mark Scheme Qn Answer Marks 1 Statement Register Main Memory Secondary Storage Data is lost during power interruption ✔ ✔ Non-volatile memory ✔ Slowest accessing speed ✔ Storage space directly used by the arithmetic logic unit and the control unit ✔ Used to transfer large amounts of data from one device to another ✔ 2 Licence Description Free and Open Source • • Software that is free for use for a period after which users will need to pay a fee to continue to use it. Public Domain • • Software where unauthorised copying of it is prohibited and its source code is kept secret. Freeware • • Software that is available as “lite” version where users may use at no cost. Shareware • • Software that is available for users to use, copy, study and modify. Proprietary • • For intellectual property that have expired or simply surrendered. 3 (a) (i) 8910 = 6410 + 1610 + 810 + 110 = 26 + 24 + 23 + 20 = 010110012 3 (a) (ii) 910 = 10012 and B16= 10112 Thus, 9B16 = 1001 10112 = 12810 + 1610 + 810 + 210 + 110 = 15510 9B16 = 16 x 9 + 11 = 15510 1

Qn Answer Marks 3 (a) (iii) 11102 = 8 + 4 + 2 and 01012 = 4 + 1 = 1410 = 510 = E16 = 516 Thus, 111001012 = E516 3 (b) (i) Unicode can encode more characters of different languages than ASCII. 3 (b) (ii) RGB colour codes, memory dumps, network address, ASCII and Unicode, URL Encoding (Any TWO) 4 Wired: Network devices are connected by a physical medium such as cables. Wireless: Signals are transmitted in the form of electromagnetic waves such as radio waves and microwaves. Wired: Less convenient when expansion required as additional wiring will be needed. Wireless: Network can be expanded easily with existing equipment. Wired: Less convenient to use as equipment needs to be connected by cables at all time. Wireless: More convenient as one can work from any location within the wireless network’s coverage area. (Any TWO) 5 (a) (i) 1. Technology and software have been able to reduce the time, cost and effort needed for payments, investments, fundraising, trading and/or data analytics for both business and individuals. 2. Algorithmic trading which is the study and refinement of algorithms to make trading decisions at speed not possible by human being can generate profits at a speed and frequency that is impossible for a human trader. 3. Artificial intelligence can be used to calculate interest rates and home values by using historical pricing charts to develop a model that more accurately predicts the financial future by taking numerous factors into account. 4. As computers can handle large volumes of information, they can take over the manual work of analyzing data and creating meaningful reports and so will be more efficient in tasks such as detecting and preventing fraud.

Qn Answer Marks 5. The use of software and technology allows for easier communication and collaboration among employees in the financial sector which in turn results in the generation of more profit for the financial institutions. (ANY TWO) (Marks to be awarded if key phrases (bold and underlined) are used.) 5 (a) (ii) 1. Cyberattacks and ease of obtaining false information on the Internet has made some people more vulnerable to financial scams and other get-rich-quick schemes. 2. Cyberattacks such as phishing and pharming can result in money loss or fraudulent activities. 3. Technology has replaced huge number of jobs in the financial sector. As such, many workers in the financial sector have lost their jobs. 4. Data stored in database of financial institutions such as banks may be corrupted, hacked or lost. This can result in loss of important data or data leakage. 5. Over-dependence on technology can lead to banking activities coming to a standstill during power outage or cyberattack such as denial-of-service. (ANY TWO) (Marks to be awarded if key words/phrases (bold and underlined) are used.) 5 (b) (i) 1. Human error Accidental damage to storage device can happen during transportation. Accidental overwriting of data can happen when multiple users are working on the same file. 2. Power Failure Data can be lost when power supply is interrupted during the process of writing from the volatile memory (e.g. RAM) onto the non-volatile storage device (e.g. hard disk) 3. Hardware failure or damage Storage device can fail due to overuse, manufacturing defects or damage. 4. Malicious software or viruses

Qn Answer Marks Malicious software or viruses may damage or corrupt data. (ANY ONE) (Marks to be awarded if key words/phrases (bold and underlined) are used.) 5 (b) (ii) 1. Make regular backups of data 2. Use adequate protection when handling/transporting storage devices. 3. Set up rules when collaborating so as to prevent accidental overwriting of data. 4. Use backup power supply or UPS (Uninterruptible Power Supply) so that the storage device can complete the writing of data in case of power failures. 5. Check storage devices regularly and replace them immediately when signs of failure are detected. 6. Install anti-virus and perform regular scans for viruses. 7. Avoid opening emails from unknown sources/suspicious web links. (ANY ONE) (Marks to be awarded if key words/phrases (bold and underlined) are used.) 6 (a) Inputs: - Name of the required primary school - A list of student names together with the name of their primary school Outputs: - Name of students from that primary school - Number of students from that primary school Processes required: - Search for all students from that primary school - Count the number of students who are from that primary school 7 (a) NOR 7 (b) A B X 0 0 1 0 1 1 1 0 1 1 1 0

Qn Answer Marks 7 (c) X = (D AND NOT T AND L) OR (NOT D AND T AND NOT L) 8 (a) num1 = 10 num2 = 20 (Any values such that num1 < num2) 8 (b) (i) num1 num2 OUTPUT “Enter first number” 1 “Enter second number” 10 “Enter first number” 20 “Enter second number” 5 TRUE 8 (b) (ii) The algorithm checks if num1 is divisible by num2. (optional: It will display TRUE if num1 is divisible by num2 and display FALSE if num1 is not divisible by num2.) 8 (c) (i) Name of validation check: Presence check Description: To check that the user has entered a value for each input, num1 and num2. Name of validation check: Format check Description: To check that the user has entered only numbers for each input, num1 and num2 (ANY ONE) 1 for name 1 for description 8 (d) Test case condition Test data Normal condition 20, 2 Error condition a, b D T L D AND NOT T [1m] AND L [1m] X NOT D AND T [2m] AND NOT L [1m] OR [1m]

9 (a) Advantage: • Program runs at a faster speed as translation has been done beforehand. • Compiler is not required to run the program after compilation is complete. Syntax errors are detected before program is run. (Any ONE) Disadvantage: • Changes to source code require recompilation before taking effect. • Does not offer interactive mode. (Any ONE) 9 (b) Python, Scratch (Any ONE) 10 (a) A5: Text B2: Percentage E9: Currency 10 (b) (i) PPMT 10 (b) (ii) (a) SUM 10 (b) (ii) (b) $B$9 11 - Initialisation of three counters for highest score (highest), highest score index (h_index) and total score of all students (total) [before loop] - Loop management for reading scores of 20 students - Input and store in list scores of 20 students (at start of loop) - Validate scores (within 0 and 100) - Totalling all students’ scores - Checking for highest score… - … updating highest score if highest score is found - … updating highest score index if highest score is found - Calculating average score of all students (outside of loop) - Outputting average score of all students (outside of loop) - Outputting index of highest score (outside of loop)

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