SRSS 2019 P1

This question paper consists of 16 printed pages including the cover page. [Turn over Name_______________________________________ ( ) Class: Sec ___________ SERANGOON SECONDARY SCHOOL PRELIMINARY EXAMINATION 2019 SECONDARY 4 EXPRESS COMPUTING 7155/01 PAPER 1 30 AUGUST 2019 Name of Setter: Mr Adrial Tan 2 hours READ THESE INSTRUCTIONS FIRST Do not open the question papers until you are told to do so. Write in dark blue or black pen in the spaces provided on the Question Paper. You may use a soft pencil for any diagrams, graphs, music or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Answer all questions. No marks will be awarded for using brand names of software packages or hardware. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. FOR EXAMINER’S USE 80

2 1 The following diagram shows five network terms and six descriptions. Draw a line between each network term to the most appropriate description. Network Term Description [5] IP Address MAC Address Service Set Identifier Ring Topology Star Topology An identifier that is automatically assigned by a router. It is required to receive and forward data packets out of a network A network configuration that requires a central device such as a hub or a bridge to manage the transmission of data. A 32-byte long string that identifies a wireless access point and all devices connected to it. A network configuration where the entire network may fail whenever any computer in the network fails. An identifier that is required to receive and forward data packets within a network through a network bridge. A network configuration where all computers are connected together through a single common cable.

3 2 (a) Convert the binary number (10000101)2 into a denary number. Show your workings. ……………………………………………………………………………………………. ……………………………………………………………………………………............ ……………………………………………………………………………………………. ……………………………………………………………………………………………. ………………………………………………………………………………………… [2] (b) Convert the hexadecimal (FB)16 into a binary number. Show your workings. ……………………………………………………………………………………………. ……………………………………………………………………………………............ ……………………………………………………………………………………………. ……………………………………………………………………………………………. ………………………………………………………………………………………… [2] (c) Convert the binary number (11110)2 into a hexadecimal number. Show your workings. ……………………………………………………………………………………………. ……………………………………………………………………………………............ ……………………………………………………………………………………………. ……………………………………………………………………………………………. ………………………………………………………………………………………… [2] (d) Convert the hexadecimal (365)16 into a denary number. Show your workings. ……………………………………………………………………………………………. ……………………………………………………………………………………............ ……………………………………………………………………………………………. ……………………………………………………………………………………………. ………………………………………………………………………………………… [2]

4 3 Study the following algorithm very carefully. 1 Highest = 1 2 OUTPUT "Enter the first integer: " 3 INPUT Num1 4 OUTPUT "Enter the second integer: " 5 INPUT Num2 6 Range = Num1 7 IF Num1 > Num2 THEN 8 Range = Num2 9 ENDIF 10 FOR i = 1 to Range: 11 IF Num1%i == 0 AND Num2%i == 0: 12 Highest = i 13 ENDIF 14 NEXT i 15 OUTPUT Highest (a) (i) Complete the following trace table for the algorithm. Use the data 15,6 as input. Highest Num1 Num2 Range i OUTPUT 1 [5]

5 (ii) State the purpose of the algorithm. Assume that users enter only positive integers for inputs Num1 and Num2. ……………………………………………………………………………………. ……………………………………………………………………………………. ………………………………………………………………………………… [1] (b) (i) The algorithm does not include validation on input. Name and describe one validation check that could be added to validate the input(s) in the given algorithm. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ………………………………………………………………………………… [2] (ii) Name two different validation checks, other than your answer to part (b)(i). 1 ………………………………………………………………………………... 2 ……………………………………………………………………………. [2] (c) Once complete, the algorithm is tested with data for normal conditions. Identify two other test case conditions that could be used to test the algorithm. For each condition, give an example of test data for this algorithm. Test Case Condition Test Data [4]

6 4 Unauthorised access occurs whenever data owned by someone is used by someone else, such as an intruder or an unknowing individual, without their permission. (a) State two reasons why unauthorised access occurs. Reason 1 ...……………………………………………………………..…………...…... …………………………………………………………………………………………….. Reason 2 ...……………………………………………………………..…………...…... ………………………………………………………………………………………… [2] (b) Describe two safety measures to prevent unauthorised access. Safety measure 1 .……………………………………………………..…………...…... ....………………………………………………………………………..………….......... ...........…………………………………………………………………………..………... Safety measure 2 .……………………………………………………..…………...…... ....………………………………………………………………………..………….... [2] (c) Intruders often use different forms of cyberattacks to gain unauthorised access to digital information. Name and describe two forms of cyberattacks. 1 …………………………………………………………………………........................ …………………………………………………………………………………………….. …………………………………………………………………………………………….. …………………………………………………………………………………………….. 2 …………………………………………………………………………........................ …………………………………………………………………………………………….. …………………………………………………………………………………………….. ………………………………………………………………………………………… [4]

7 5 A computer is a device that can be programmed to accept data inputs, process it into useful information, and output the information meaningfully or store the information away. (a) The following table contains two household devices typically found at home with computers in them. For each device, name one input and one output component that can be found in them. Household Device Input Component Output Component Washing Machine Smart Mobile Phone [4] (b) Name the component that is responsible for processing data in a computer and describe its functions. Name of component …………………………………………………………………… ……………………………………………………………………………………………. Functions ……………………………………………………………………………….. ……………………………………………………………………………………………. ……………………………………………………………………………………………. ………………………………………………………………………………………… [3] (c) Identify one type of secondary storage. Give an example of the storage device, state the medium of storage and state one advantage of the named storage device. Storage device …………………………………………………………………………. Medium of storage ……………………………………………………………………... Advantage ………………………………………………………………………………. ………………………………………………………………………………………... [3]

8 6 An alarm, X, sends a signal (X = 1) when certain fault conditions in a chemical manufacturing plant are detected. The inputs are: Input Binary Value Condition F 1 Overflow detected 0 Overflow not detected T 1 Temperature >= 185 °C 0 Temperature < 185 °C P 1 Pump ON 0 Pump OFF The alarm, X, returns a value of 1 if: either (i) Temperature >= 185 °C AND Overflow detected or (ii) Overflow detected AND Pump is OFF (a) Draw the logic circuit for the above system. [4] F T P X

9 (b) Complete the truth table for the above system. F T P Working Space 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 [4]

10 7 A pseudo-code algorithm: • allows player 1 to input a number • allows player 2 to guess and input the number entered by Player 1 until the correct answer in given • stores the wrong guesses into a list • outputs a message to show if the guess is wrong • outputs a message to show if the guess is correct • stops getti