CTSS 2019 P1

[Turn over Name: _____________________ Register Number: ______ Class: _______ Clementi Town Secondary School Preliminary Examination 2019 Secondary 4 Express Computing 7155/01 26 August 2019 2 hours Candidates answer on the Question Paper. CLEMENTI TOWN SECONDARY SCHOOL CLEMENTI TOWN SECONDARY SCHOOL CLEMENTI TOWN SECONDARY SCHOOL CLEMENTI TOWN SECONDARY SCHOOL CLEMENTI TOWN SECONDARY SCHOOL CLEMENTI TOWN SECONDARY SCHOOL CLEMENTI TOWN SECONDARY SCHOOL CLEMENTI TOWN SECONDARY SCHOOL CLEMENTI TOWN SECONDARY SCHOOL CLEMENTI TOWN SECONDARY SCHOOL CLEMENTI TOWN SECONDARY SCHOOL CLEMENTI TOWN SECONDARY SCHOOL CLEMENTI TOWN SECONDARY SCHOOL CLEMENTI TOWN SECONDARY SCHOOL CLEMENTI TOWN SECONDARY SCHOOL CLEMENTI TOWN SECONDARY SCHOOL CLEMENTI TOWN SECONDARY SCHOOL CLEMENTI TOWN SECONDARY SCHOOL CLEMENTI TOWN SECONDARY SCHOOL CLEMENTI TOWN SECONDARY SCHOOL READ THESE INSTRUCTIONS FIRST Do not open the booklet until you are told to do so. Write your name, register number and class on all the work you hand in. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Approved calculators are allowed. Answer all questions. The number of marks is given in brackets [ ] at the end of each question or part question. You should show all your working The total number of marks for this paper is 80. _______________________________________________________________________ This question paper consists of 11 printed pages, including this cover page. For Examiner’s Use 80

2 Clementi Town Secondary School Computing Secondary 4 Express Preliminary Examination 2019 Answer all the questions. 1 Write down THREE considerations when deciding on an external storage device. [3] 2 The following passage describes how the data flow when the computer is switched on. Fill in the blanks with the following helping words. [5] instructions basic input/output system (BIOS) ROM operating system power-on self-test (POST) The computer loads instructions for performing a from to ensure that all the hardware components are functioning properly. The computer then loads the from ROM. The BIOS provides basic on how to communicate with hardware components as well as where to look for an operating system. Assuming that an is found on the computer’s hard drive, its data and instructions are then loaded from the hard drive into RAM. 3 The following diagram shows the specification of the processor in 2 computers. (a) Write down 2 factors that affects the performance of a processor. [2] (i) (ii) (b) Using the 2 factors stated in (a), explain why Computer 1 will perform better than Computer B in its processing ability. [2] Computer 1 Injel T9 Quad-Core 2.7GHz Computer 2 Injel T8 Duo-Core 2.5GHz

Clementi Town Secondary School 3 Preliminary Examination 2019 Secondary 4 Express Computing [Turn over 4 A palindrome is a word, phrase, number or sequence of words that reads the same backwards as forwards. An English teacher is trying to write a program that helps him to identify palindromes. (a) Identify the input required. [1] (b) Suggest ONE form of data validation he could implement in the program and explain why. [2] (c) Write down the possible output(s) of the program. [2] 5 (a) Convert the hexadecimal number (CD7)16 to denary. [2] Answer: (b) Convert the binary number (1101 1011)2 to hexadecimal. [2] Answer: (c) Convert the denary number (3172)10 to hexadecimal. [2] Answer:

4 Clementi Town Secondary School Computing Secondary 4 Express Preliminary Examination 2019 6 The following pseudo-code is for an algorithm that sums up only the ODD integers from an input of 100 integers and outputs the result. Line 1 2 3 4 5 6 7 8 9 10 Count = 0 Sum = 1000 WHILE Count < 101 INPUT Number IF Number is even Sum = Sum ** Number ENDIF count = count + 1 ENDWHILE OUTPUT sum There are FOUR errors in this pseudo-code. Locate the errors by stating the line number and state the correct pseudo-code. (a) Error 1: [1] Correction: [1] (b) Error 2: [1] Correction: [1] (c) Error 3: [1] Correction: [1] (d) Error 4: [1] Correction: [1] 7 Explain the use of parity bits during data transmission [2]

Clementi Town Secondary School 5 Preliminary Examination 2019 Secondary 4 Express Computing [Turn over 8 The Python Turtle is an interesting way to learn programming. To start using the Turtle, an instance of the turtle “bob”, with the shape of the turtle is created as shown below. Code Image import turtle bob = turtle.Turtle() bob.shape("turtle") #to initialize the turtle to face upwards bob.left(90) Using the space below, write down the codes to produce the image on the right. The following codes may help you in the implementation of the image. bob.right(90) – turtle turns right 90 degrees. bob.left(90) – turtle turns left 90 degrees. bob.forward(50) – turtle moves forward 50 pixels. Code Image #continue your answer here [6]

6 Clementi Town Secondary School Computing Secondary 4 Express Preliminary Examination 2019 9 “PayPal scammers might send out an attack email that instructs them to click on a link in order to rectify a discrepancy with their account. In actuality, the link leads to a fake PayPal login page that collects a user’s login credentials and delivers them to the attackers.” Taken from https://www.tripwire.com/state-of-security/security-awareness/ (a) Identify the cyber-attack mentioned in the passage above. [1] (b) For the cyber-attack mentioned in (a), write down TWO ways in which you can identify the cyber-attack. [2] (c) State TWO other forms of cyber-attacks. [2] (d) Give a brief description for each cyber-attack mentioned in (c). [2] (i) (ii)

Clementi Town Secondary School 7 Preliminary Examination 2019 Secondary 4 Express Computing [Turn over 10 (a) Complete the truth table for the following logic circuit: [4] A B C Working X 0 0 0 0 0 1 0 1 0 0 1 1 1 0 0 1 0 1 1 1 0 1 1 1 X A B C

8 Clementi Town Secondary School Computing Secondary 4 Express Preliminary Examination 2019 (b) A washing machine employs basic logic to carry out its washing. The inputs to the system are: Input Binary Value Condition W (weight) 1 Weight of clothes detected. 0 Weight of clothes not detected. X(water) 1 Water is turned on. 0 Water is turned off. Y(switch) 1 Machine is switched on. 0 Machine is switched off. The system will sound an alarm when certain conditions are detected. Alarm (Z) will sound (=1) when: there are no clothes or there is no water Draw a circuit diagram to represent the above system. [5] W X Y Z

Clementi Town Secondary School 9 Preliminary Examination 2019 Secondary 4 Express Computing [Turn over 11 The following spreadsheet uses the FV function to analyse the ending balance of several different bank investments. The initial inv