CWSS 2020 Computing P1

1 COMMONWEALTH SECONDARY SCHOOL PRELIMINARY EXAMINATION 2020 COMPUTING Paper 1 (Theory) Name: _____________________________________ ( ) Class: ___________ SECONDARY FOUR EXPRESS/NORMAL ACADEMIC Wednesday 2nd September 2020 7155 / 01 0800 – 1000 2 h READ THESE INSTRUCTIONS FIRST Candidates answer on the Question Paper. No Additional Materials are required. Answer all questions. 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. 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. Name of setter: Mrs Leong Sai Hong For Examiner’s Use Parent’s / Guardian’s Signature: _____________________ / 80 This paper consists of 12 printed pages including the cover page. [Turn over]

2 1 The table below contains statements about types of memory or storage. Tick (✔) one or more boxes in each row to indicate if the statement is about register, main memory or secondary storage. Statement Register Main Memory Secondary Storage Data is lost during power interruption Non-volatile memory Slowest accessing speed Storage space directly used by the arithmetic logic unit and the control unit Used to transfer large amounts of data from one device to another [5] 2 Match each of the following types of licences to its description. Licence Description Free and Open Source • • Software that is free for use for a period after which users will need to pay a fee to continue to use it. Public Domain • • Software where unauthorised copying of it is prohibited and its source code is kept secret. Freeware • • Software that is available as “lite” version where users may use at no cost. Shareware • • Software that is available for users to use, copy, study and modify. Proprietary • • For intellectual property that have expired or simply surrendered. [5]

3 3 (a) Convert the (i) denary number 89 into a 8-bit binary number. ________________________________________________________ ________________________________________________________ [1] (ii) hexadecimal number 9B into a denary number. ________________________________________________________ ________________________________________________________ [1] (iii) binary number 11100101 into a hexadecimal number. ________________________________________________________ ________________________________________________________ [1] (b) (i) ASCII and Unicode are two applications of the hexadecimal number system. Explain why Unicode is a preferred choice over the ASCII standard for character encoding. ________________________________________________________ ________________________________________________________ ________________________________________________________ [1] (ii) State two other examples where hexadecimal is used to represent binary. ________________________________________________________ ________________________________________________________ [2] 4 Describe two differences between wired and wireless networks. 1. ________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ 2. ________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ [2]

4 5 (a) Technology is widely used in the financial sector. (i) Describe two economic benefits of using technology in the financial sector. 1. __________________________________________________ ________________________________________________________ ________________________________________________________ [1] 2. __________________________________________________ ________________________________________________________ ________________________________________________________ [1] (ii) Describe two negative impacts of using technology in the financial sector. 1. __________________________________________________ ________________________________________________________ ________________________________________________________ [1] 2. __________________________________________________ ________________________________________________________ ________________________________________________________ [1] (b) Give one type of causes for data corruption and loss and their corresponding preventive measures. (i) Cause ________________________________________________________ ________________________________________________________ ________________________________________________________ [1] (ii) Preventive measure ________________________________________________________ ________________________________________________________ ________________________________________________________ [1]

5 6 A teacher wants to find out how many students in the school came from a certain primary school and who they are. State the inputs, the outputs and the processes. Inputs _____________________________________________________________ __________________________________________________________________ __________________________________________________________________ Outputs ___________________________________________________________ __________________________________________________________________ __________________________________________________________________ Processes required __________________________________________________ __________________________________________________________________ __________________________________________________________________ [6] 7 (a) Identify the logic gate represented by the following truth table. A B X 0 0 1 0 1 0 1 0 0 1 1 0 _____________________________________________________________ [1] (b) Draw a truth table for a NAND gate. [1]

6 (c) An alarm in a microwave oven sounds when certain conditions occur. The output, X, of a logic circuit that drives the alarm must have a value of 1 if: either door is close and temperature < 100ºC and light is on or door is open and temperature > 100 ºC and light is off The inputs to the system are: Input Binary Condition D 0 Door open 1 Door close T 0 Temperature < 100ºC 1 Temperature > 100ºC L 0 Light off 1 Light on Draw a logic circuit for the system. [6]

7 8 Study the following algorithm very carefully. 1 done = FALSE 2 WHILE num1 < num2 3 OUTPUT “Enter first number” 4 INPUT num1 5 OUTPUT “Enter second number” 6 INPUT num2 7 ENDWHILE 8 IF num1 MOD num2 == 0 9 done = TRUE 10 ELSE 11 done = FALSE 12 ENDIF 13 OUTPUT done (a) num1 and num2 need to be initialised before the above algorithm is run. State a set of possible values for num1 and num2. num1 = ______________________________________________________ num2 = ______________________________________________________ [2] (b) (i) Complete the following trace table for the algorithm. Use the data 1, 10, 20, 5 as input. num1 num2 OUTPUT [3] (ii) State the purpose of the algorithm. _______________________________________________________ _______________________________________________________ [1]

8 (c) The algorithm has only one type of validation check. Name and describe another one validation check that could be added to val