ZHSS 2020 Computing P1 Solution

Setter: Mr. Calvin Heng Vetter: Mr. Low Kee Ley This question paper consists of 13 printed pages including this cover page. ZHONGHUA SECONDARY SCHOOL PRELIMINARY EXAMINATION 2020 SECONDARY 4 EXPRESS Candidate’s Name Class Register Number MODEL ANSWER TOS COMPUTING 7155/01 Paper 1 18 September 2020 2 hours Additional Materials: NIL READ THESE INSTRUCTIONS FIRST Write your index number and name on all the work you hand in. Write in dark blue or black pen on both sides of the paper. You may use a pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Answer all the questions. Write your answers in this question booklet. Give non-exact numerical answers correct to 3 significant figures, or 1 decimal place in the case of angles in degrees, unless a different level of accuracy is specified in the question. The use of a scientific calculator is expected, where appropriate. You are reminded of the need for clear presentation in your answers. At the end of the presentation, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. The total number of marks for this paper is 80. For Examiner’s Use:

2 1 (a) Convert 8 bits into GB. 8 bits = 1 byte 1byte x 10-3 x 10-3 x 10-3 = 1.00 x 10-9 GB (3sf) KB MB GB [1] (b) Convert 64 Terabytes into KB. 64 x 103 x 103 x 103 = 64 x 109 = 6.40 x 1010 KB (3sf) GB MB KB [1] 2 Draw a line to match the terms to its correct description. Terms Description DoS Attack l Cookie l l A small piece of data used by websites to store personal information on a user’s web browser. Encryption l l Hidden program that secretly collects personal information. Phishing l l Flooding network with useless traffic, making the network slow or inaccessible. Software piracy l l Sending fake or spoof emails. Spyware l [4]

3 3 Fill in the blanks with the helping words. ALU APPLICATION RAM CPU ROM UTILITY (a) RAM is high speed, volatile memory. (b) The accumulator stores intermediate results of calculations in the ALU . (c) Antivirus software is an example of UTILITY a software. (d) ROM tells the CPU how to boot up. [4] 4 Fiona is a graphic designer for a publishing company. The image editing software that she uses represents each unique colour as a six digit hexadecimal code. (a) As a power of 16, how many possible unique colours could Fiona use? (workings must be shown clearly) 6 digits of 16 possibilities: = 16 x 16 x 16 x 16 x 16 x 16 = 16,777,216 colours [2] (b) Explain one benefit to programmers of using hex codes to represent the different colours. It would be easier to remember the hexadecimal code for a particular colour BECAUSE Hexadecimal codes are shorter and more convenient to handle than the binary equivalent. [2]

4 5 The use of technology has impacted our lives in many areas. Describe two advantages and two disadvantages of the impact of technology on healthcare. Advantage 1 Telemedicine – use of video conferencing and other technology for doctors to provide medical consultations and diagnoses over the internet. Advantage 2 Use of robots to dispense medicine and performance of other menial tasks. Disadvantage 1 Misuse of medical information from the internet leading to potentially dangerous decisions based on incorrect diagnoses. Disadvantage 2 Some people find the use of robots and other technology impersonal and distrust the ability of machines to provide proper healthcare. [4]

5 6 Access to a computer system is becoming more sophisticated. One area of major development is in user authentication. (a) Describe what is authentication and how it works? It is the process of verifying the identity of a user. It requires the user to prove his identity by providing evidence from categories such as a password; or use of a mobile phone; and or smart phone or body part (e.g. face). [2] (b) One way to conduct authentication is to use two-factor authentication. Explain how two-factor authentication works using a one-time-password (OTP) on the users’ mobile phone. To access the computer system, the user has to confirm his identity by providing a secret password. The system generates a one-time password (OTP) and sends it to the user on his mobile phone. The user then enters this OTP to gain access. [2] (c) Suggest another way to implement two-factor authentication. Using a security token (hardware device that has a small screen and a few buttons, issued by the website/business concern. The security token generates the OTP and the user enters this OTP to gain access. [2]

6 7 Besides optical technology storage devices, name two other types of external storage technologies found in a computer system. List their corresponding example and describe each of them in terms of their advantage and disadvantage. Type 1 : MAGNETIC STORAGE Example: HARD DISKS Description Advantage: Cheap, Reliable, Huge Capacity, Easy to transport. Disadvantage: Heavy. Takes up space. Sensitive to heat, vibration. {Any 1 Advantage and 1 Disadvantage} [3] Type 2 : SOLID STATE DEVICE Example: THUMB DRIVE Description: Advantage: Small form factor – Easy to transport, Very large storage capacities (hundreds of gigabytes) Disadvantage: Expensive, Delicate, Easily misplaced due to small size. {Any 1 Advantage and 1 Disadvantage} [3]

7 8 Study the Boolean statement: Q = (NOT A AND B) OR (NOT B and C) (a) Complete the truth table for the Boolean statement above. A B C NOT A NOT A * B NOT B NOT B * C Q 0 0 0 1 0 1 0 0 0 0 1 1 0 1 1 1 0 1 0 1 1 0 0 1 0 1 1 1 1 0 0 1 1 0 0 0 0 1 0 0 1 0 1 0 0 1 1 1 1 1 0 0 0 0 0 0 1 1 1 0 0 0 0 0 [2] (b) Draw a logic circuit for the Boolean statement above. [4] A B C Q

8 9 Dr Heng records a patient’s temperature once an hour for six hours. Any time the temperature is > 37C, an incidence of fever is recorded. The average of all temperatures taken is calculated at the end. (a) Before you complete the trace table, calculate the average temperature (to one decimal place) using the following test data: 36, 36, 38.5, 37, 38, 36 Expected result = _36.9__________ (b) Complete the trace table using the temperatures above. Line Pseudocode 010 temp ß 0 020 fever ß 0 030 total ß 0 040 hour ß 1 050 WHILE hour < 7 060 OUTPUT “Enter Temp: “ 070 temp ß USERINPUT 080 IF temp > 37 THEN 090 fever ß fever + 1 100 END IF 110 total = total + temp 120 hour = hour + 1 130 ENDWHILE 140 average ß ROUND(total/hour, 1) # round to 1 decimal place 150 OUTPUT “Average Temp: “, average 160 OUTPUT “Fever Incidents: “, fever temp fever total hour average OUTPUT 0 36 36 38.5 37 38 36 0 1 2 0 36 72 110.5 147.5 185.5 221.5 1 2 3 4 5 6 7 31.6 Enter Temp: Enter Temp: Enter Temp: Enter Temp: Enter Temp: Enter Temp: Average Temp: 31.6 Fever incidents: 2 Grade by columns. Deduct 1 mark for each incorrect column. [5] (c) Is the algorithm correct? If not, write your change to the pseudo-code below so that it gives the correct results. NO. Line 040 change to hour ß 0 and while hour < 6 Line 140 average <- round(total/(hour-1), 1) [1]

9 {state position and code change} 10 The spreadsheet below shows the information of a shopping list. (a) The spreadsheet above contains: _18_ rows and _6_ columns. [1] (b) The most likely function used in cell E4 is: [1