SRSS 2020 P1 Solution

1 Serangoon Secondary Computing Sec 4E 2020 Preliminary Exams (Marking scheme) Q1a) [4 m] Logic gates Boolean Values A B X 0 0 1 0 1 1 A B X 0 0 0 1 1 1 A B X 0 1 0 1 1 0 A B X A B X A B X A B X

2 Q1b) [5m] X = (A OR (NOT B NAND C)) AND (A NOR B) Q1c) [4 m] A B C D (NOT B) E (D NAND C) F (A OR E) G (A NOR B) X (F AND G) 0 0 0 1 1 1 1 1 0 0 1 1 0 0 1 0 0 1 0 0 1 1 0 0 0 1 1 0 1 1 0 0 1 0 0 1 1 1 0 0 1 0 1 1 0 1 0 0 1 1 0 0 1 1 0 0 1 1 1 0 1 1 0 0 B A C X

3 Q2) [5 m] (a) The network interface card is the hardware interface that enables the transfer of data between a device and a network. (b) The network switch is a device that constructs a single network by connecting two similar networks together. (c) The modem is a device responsible for modulating and demodulating digital data when data is transmitted over long distances. (d) The router is a device that forwards packets between separate networks. (e) The network hub is a device that transmits received packets to all connected devices. Q3a) [4 m] Any 2 social benefits from: • Enabled communication between people without face-to-face meetings. • Enabled students to learn from home through the use of online learning tools and virtual classrooms tools. • Allowed people to entertain themselves while staying at home (e.g. mobile gaming communities, live video streaming etc) • Keep people updated with latest news. • Encourages community driven efforts that benefits the society during the lockdown (e.g. donation drives, food distribution drives etc) • Any other relevant answers. Any 2 economic benefits from: • Allowed business to reach out to customers through online marketing and social media when retail businesses were required to shutdown. • Reduced business costs from overseas travel with the use of cheap and effective video conferencing tools in place of face-to-face meetings. • Enabled consumers to spend, borrow, invest and save money through electronic applications without the need for face-to-face interactions. • Create job opportunities such as online food delivery and delivery. • Any other relevant answers. Q3b) [2 m] Any 2 negative impacts from: • People are easily misled by the spreading of rumours and false information online. • Cyberattacks and cybercrimes targeted at vulnerable groups of people lead to loss of money. • Increase in cyber addiction rates which may lead to deficiency in real-life social skills and abandoning of responsibilities. • Excessive screen time may lead to health problems (e.g. insomnia, eyestrain, increased anxiety etc). • Any other relevant answers

4 Q4a) [2 m] (1 0 0 1 0 1 1 0)2 = 21 + 22 + 24 + 27 = 2 + 4 + 16 + 128 = 150 Q4b) [2 m] Denary Quotient Remainder 459 28 11 (B) 28 1 12 (C) 1 0 1 459 = 1CB16 Q4c) [3 m] Any 3 relevant points from: • Represented by 3 bytes of data (6 hexadecimal digits); 1 byte of data to repres