SST 2020 Computing P1 Solution

1 2020 SEC 4 COMPUTING PRELIM EXAM MARKING SCHEME Qn 1 Marking Scheme / Answer Marks (a) Roles arithmetic logic unit • address bus • control unit • data bus • process register • RAM • ROM • Description • Data storage space that is extremely fast but small. It is physically located inside the processor and cannot be changed without changing the processor. • Transports required memory location from processor to memory; uni-directional • Where data and instructions are stored temporarily so that they can be quickly accessed by the processor when needed. • Part of the processor that follows instructions and decides when data should be stored, received or transmitted by different parts of the computer. Qn 2 Marking Scheme / Answer (a) American Standard Code for Information Interchange (b) 716 = 1112 C16 = 11002 (7C)16 = 11111002 (c) 10111002 = 26 + 24 + 23 + 22 = 64 + 16 + 8 + 4 = 9210 (d) 109 / 16 = 6 R 13 13 / 16 = 0 R 13 (109)10 = 6D16 (e) IPv4 uses 4 bytes IPv6 uses 16 bytes Qn 3 Marking Scheme / Answer (a) - Positive: Technology has provided better videos, simulations and collaboration tools for lessons to be more engaging and relevant. - Positive: Open sharing of information has made education accessible to all, even learners from disadvantaged backgrounds. - Negative: Students’ attention spans are getter shorter as they are more distracted by technology and social media.

2 - Negative: Students are more prone to gaming and internet addiction. - Negative: Students are more prone to cyberbullying (b) Similarity: Both are computer programs that copy themselves and sends copies of themselves to other programs or computers. Difference: A worm does not need to attach itself to an existing program while a virus does. Qn 4 Marking Scheme / Answer (a) Access Control / Authorisation Authentication Understanding of Private Policies Biometrics ✓ Cloud Services ✓ Encryption ✓ Firewalls ✓ Passwords ✓ Social Networking sites ✓ (b) 2FA stands for two-factor authentication. It is a form of authentication that uses evidence from something the user knows And something the user owns. Qn 5 Marking Scheme / Answer Inputs: - Name of Runner, - Gender of Runner (Girl or Boy) - Timing of Runner Processes: - For each gender compare the timing of students and find the name of student with minimum timing, and the respective timing itself. - Store all data in array/list - Sort data into each gender Qn 6 Marking Scheme / Answer (a) - Shared resources: a network allows a group of computers to make use of shared resources such as printers or files. - Shared internet access: depending on the network’s configuration, every user who logs on to the network may have access to the internet. - Shared software: Software can be stored on the central server of a network and deployed to other computers over a network. - Shared storage: Data files can be stored on a central server for ease of access and backup purposes. - Communication: Computers in the same network are often able to share instant messages and emails for communication.

3 (b) - Wireless has higher mobility of users, who can move about freely within the range of the wireless network. - It is easier to add new devices to the network as the router can be easily configured. - Wireless is more organised without cables. (c) - Wireless is generally slower due to lower bandwidth and possible interference from radio waves or microwaves - Wireless is less secure and reliable due to intrusion by hackers. Qn 7 Marking Scheme / Answer (a) Device I: Hub Device II: Bridge (b)(i) - A network interface card provides the hardware interface to enable the transfer of data between a device and a network. - An NIC may connect to a network physically or wirelessly. (b)(ii) A SSID is a string of up to 32 bytes that identifies a wireless access point (WAP) all the devices connected to it. (b)(iii) - A packet is a unit of broken-up data - containing a header with information about the source and destination that are needed for transmission. Qn 8 Marking Scheme / Answer (a) COUNTA (b) PPMT (c) CEILING (d) HLOOKUP Qn 9 Marking Scheme / Answer Error 1: Line 3 Correction 1: Odd = 0 Error 2: Line 6 Correction 2: If Num MODULO 2 = 0 Error 3: Line 10 Correction 3: (Indentation should be 4 spaces less) Counter = Counter + 1 Error 4: Line 11 Correction 4: UNTIL Counter = 20 Qn 10 Marking Scheme / Answer (a)

4 Correct use of NOT gate – 1 mark Correct use of AND gate – 1 mark Correct use of OR gate – 1 mark (b) A D T P Q R S X 0 0 0 1 1 0 1 1 0 0 1 1 1 0 1 1 0 1 0 1 0 0 0 0 0 1 1 1 0 1 0 1 1 0 0 0 1 0 0 0 1 0 1 0 1 0 0 0 1 1 0 0 0 0 0 0 1 1 1 0 0 1 0 1 1 Column 1 Mark (c) ((NOT A) AND (NOT D)) OR (D AND T) Qn 11 Marking Scheme / Answer Suggested answer O(N2) FOR x ← 1 to N, inclusive FOR y ← x+1 to N, inclusive IF WsMarks[x] > WsMarks[y] AND WsMarks[x] > (30 * 0.75) OUTPUT WsMarks[x] ENDIF NEXT NEXT Keywords (correct + capitalization Overall presentation OR Suggested answer O(N) max_so_far ← -1 FOR x ← N to 1, inclusive IF WsMarks[x] > max_so_far AND WsMarks[x] > (30 * 0.75) OUTPUT WsMarks[x] max_so_far ← WsMarks[x] ENDIF NEXT

5 Keywords (correct + capitalization Overall presentation Qn 12 Marking Scheme / Answer Suggested Answer O(N3)

6 Three for-loops (2pt each) Check and Output solution Overall presentation OR Suggested Answer O(N2) Two for-loops (2pt each) Calculate a2 + b2 Calculate c Check and output solution Overall presentation

7 Qn 13 Marking Scheme / Answer (a) L a b OUTPUT [0, 0, 0, 0] [1, 0, 0, 0] 1 1 [1, 1, 0, 0] 0 2 2 [1, 1, 1, 0] 1 [1, 2, 1, 0] 0 3 3 [1, 2, 1, 1] 2 [1, 2, 3, 1] 1 [1, 3, 3, 1] 0 4 3 [1, 3, 3, 4] 2 [1, 3, 6, 4] 1 [1, 4, 6, 4] 0 5 3 [1, 4, 6, 10] 2 [1, 4, 10, 10] 1 [1, 5, 10, 10] 0 6

8 10 (One column one mark) (b) The algorithm is used to calculate the Binomial Coefficient of the k+1 th term of (x + y)N, or the value of NCK