ZHSS 2018 P1

Setter: Mr. Calvin Heng Vetter: Mr. Low Kee Ley This question paper consists of 14 printed pages including this cover page. ZHONGHUA SECONDARY SCHOOL PRELIMINARY EXAMINATION 2018 SECONDARY 4 EXPRESS Candidate’s Name Class Register Number COMPUTING 7155/01 Paper 1 13 September 2018 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 Define the term ‘computer’. [3] _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ It is said that the modern smartphone is a computer. From your definition above, describe two areas where the smartphone meets the requirements of the definition. [2] _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________

3 2 Number Systems. All workings must be shown clearly. (a) Convert the Hexadecimal number 4D to Denary: [2] _____________________________________________________________ (b) Convert the Binary number 101011110101 to Hexadecimal: [2] _____________________________________________________________ (c) Convert the Denary number 844 to Hexadecimal: [2] _____________________________________________________________ (d) Convert the Binary number 1010111111001000 to Denary: [2] _____________________________________________________________ 3 Data Protection. (a) Study the following exhibit. Is this a case of data loss or data corruption? Explain your answer briefly. [2] _____________________________________________________________ _____________________________________________________________ (b) Describe one way to prevent Data Loss. [1] _____________________________________________________________ _____________________________________________________________

4 4 Complete the following table by writing in the type of Malicious Software next to its description. Type of Malicious Software Description (a) A hidden program that secretly collects personal information about its users and transmits this information to attackers without the users’ knowledge. [1] (b) A computer program that runs automatically and attempts to spread by sending copies of itself to other computers, without the need to attach itself to an existing program. [1] (c) A computer program that pretends to be a harmless file or useful application, but when activated, does harmful things like grant unauthorised access to the computer. [1] 5 For the following scenarios, state whether the person described is guilty of copyright infringement, plagiarism, or both by putting a tick ( ü ) in the box. Scenario Copyright Infringement Plagiarism [4] (a) Jason takes his friend’s python program and submits it for a contest as his own program without his friend’s permission. (b) Jason installs a crack on a software application so that he can use it for free. (c) Jason found a programming solution on a public domain website and submits it as his own work for an assignment.

5 6 Study the problem statement below and answer the questions: Problem Statement Your 70-year-old grandma is trying to access her Central Provident Fund information on the www.cpf.gov.sg website. As she knows you are a student of Computing, she requests for your help in logging in. You are presented with the following screen: (a) What are the inputs for this screen? [3] _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ In order to improve security, websites use two-factor authentication. [2] What is two-factor authentication? _____________________________________________________________ _____________________________________________________________ The next screen shows two-factor authentication in action. (c) Describe how the process works here, using her mobile phone. [1] _____________________________________________________________ _____________________________________________________________

6 7 Study the following program code: Annotate the program with the following Labels: LABEL STATEMENT (a) A Sub-Goal Labelling {Has been done for you as an example} (b) B Iteration over Condition Statement [1] (c) C Iteration over Sequence Statement [1] (d) D Selection Statement [1] 8 Study the following program carefully: Line Program Code ----- ------------------- 001 def dectobin(n): 002 binary = 0 003 while str(n): 004 if n // 2 == 0: 005 binary += ‘0’ 006 else: 007 binary += ‘1’ 008 n = n // 2 009 return ‘’.join(reversed(result)) Import math #Function returns True if input integer is even, False otherwise def is_even(q): return q % 2 == 0 #Function returns the sum of the squares of two integers def sum_of_squares(x, y): return x * x + y * y #Function returns the area of a circle with radius r def area_of_circle(r): return math.pi * r * r #Main body of Program #Find area of circle from r = 0 to r = 100 for I in range(101): print(“Area of Circle “, i, “ is “, area_of_circle(i)) #Find sum of squares from 100,100 to 1,1 for even numbered j j = 100 k = 100 while j > 0: if is_even(j): print(“Sum of squares of “, j, “ and “, k, “ is “, sum_of_squares(j, k) j -= 1 k -= 1

7 The programmer tests this program by issuing the following commands: print(dectobin(2)), with expected result as: ‘10’ Print(dectobin(10)), with expected result as: ‘1010’ Unfortunately, errors of various kinds start to appear. Please help to debug the program. There are four errors in this program. Locate the errors (state the line number) and state the correction in the program: (a) Error 1: [2] _____________________________________________________________ Correction: _____________________________________________________________ (b) Error 2: [2] _____________________________________________________________ Correction: _____________________________________________________________ (c) Error 3: [2] _____________________________________________________________ Correction: _____________________________________________________________ (d) Error 4: [2] _____________________________________________________________ Correction: _____________________________________________________________

8 9 Study the program (