XMSS 2020 P1

2 7155/01/Computing/2020 Preliminary Exam For Examiner’s Use

3 7155/01/Computing/2020 Preliminary Exam For Examiner’s Use 1 A computer has many different components.

4 7155/01/Computing/2020 Preliminary Exam For Examiner’s Use Study each statement. Tick to show whether the statement is True or False. Statement True False Registers are physically located inside the processor. Data on the address bus travels bi-directionally. Data and instructions on the ROM are used for startup only. Typically, solid state type of storage device transfers data faster than magnetic but slower than optical storage devices. [4] 2 Hexadecimal notation is often used in computing. (a) List two uses of hexadecimal notation in computer science. 1 ………………………………………………………………………………………. 2 ………………………………………………………………………………………. [2] (b) State two advantages of using hexadecimal notation to represent binary values. 1 ………………………………………………………………………………………. …………………………………………………………………………………………. 2 ………………………………………………………………………………………. …………………………………………………………………………………………. [2] 3 Decomposition, Pattern Recognition and Generalisation are three common problem solving techniques. (a) Decomposition is a technique of breaking down a complex problem into smaller parts. (i) Describe how it helps in problem-solving and algorithm design. …………………………………………………………………………………... …………………………………………………………………………………... …………………………………………………………………………………... [2]

5 7155/01/Computing/2020 Preliminary Exam For Examiner’s Use (ii) One approach to decomposing is modularity. Describe what this is. …………………………………………………………………………………... …………………………………………………………………………………... …………………………………………………………………………………... [2] (b) What is Pattern Recognition? How is it useful to solving problems? …………………………………………………………………………………………. …………………………………………………………………………………………. …………………………………………………………………………………………. …………………………………………………………………………………………. [3] 4 A computer network is a system of two or more computers that are connected together by a transmission medium for the exchange of data. (a) Modem is a device responsible for modulation and demodulation? What is modulation? …………………………………………………………………………………………. …………………………………………………………………………………………. …………………………………………………………………………………………. [2] (b) What is the function of a router? …………………………………………………………………………………………. …………………………………………………………………………………………. …………………………………………………………………………………………. [2] (c) State and explain one advantage of a wired network over a wireless network. …………………………………………………………………………………………. …………………………………………………………………………………………. …………………………………………………………………………………………. [2] (d) State and explain one advantage of a wireless network over a wired network. …………………………………………………………………………………………. …………………………………………………………………………………………. …………………………………………………………………………………………. [2]

6 7155/01/Computing/2020 Preliminary Exam For Examiner’s Use 5 Data can become corrupted or lost due to malicious software. (a) Identify two methods to prevent our computers from malicious software. 1 ………………………………………………………………………………………. …………………………………………………………………………………………. 2 ………………………………………………………………………………………. …………………………………………………………………………………………. [2] (b) Describe the following terms and explain how they could be used in cyberattacks. Your description must clearly state the difference between the two terms. Phishing ………………………………………………………………………………. …………………………………………………………………………………………. …………………………………………………………………………………………. Pharming ……………………………………………………………………………. …………………………………………………………………………………………. …………………………………………………………………………………………. [4] 6 Source codes are translated into machine codes using compiler or interpreter. (a) Describe an interpreter. …………………………………………………………………………………………. …………………………………………………………………………………………. …………………………………………………………………………………………. [2] (b) State two advantages that it has over a compiler. 1. ……………………………………………………………………………………... ……………………………………………………………………………………..…. 2. ……………………………………………………………………………………... ……………………………………………………………………………………..…. [2] (c) State two disadvantages that it has compared to a compiler. 1. ……………………………………………………………………………………... ……………………………………………………………………………………..…. 2. ……………………………………………………………………………………... ……………………………………………………………………………………..…. [2]

7 7155/01/Computing/2020 Preliminary Exam For Examiner’s Use 7 You are required to write an algorithm that: • accepts an input of a string • outputs the number of letters in the string • outputs the number of digits in the string • outputs the number of characters in the string that is not letter and not digit Write the algorithm using pseudo-code or flowchart. [8]

8 7155/01/Computing/2020 Preliminary Exam For Examiner’s Use 8 A school wants to know how many of its Secondary 1 students needs to be put in the PRIDE programme (for students whose BMI is greater than 27.0). BMI is calculated using the formula BMI = mass (in kilograms)/height2 (in metres) Study the following pseudo-code. Count_student = 0 Total_for_pride = 0 INPUT number_sec_1 WHILE Count_student <= number_sec_1 DO INPUT weight INPUT height bmi = weight / height * height IF bmi >= 27.0 THEN Total_for_pride = Total_for_pride + 1 ENDIF ENDWHILE OUTPUT Total_for_pride (a) There are four errors in the given algorithm. State each error and write the correct pseudo-code. Error 1 ……………………………………………………………………………………… Correction ……………………..…………………………………………………………… Error 2 ……………………………………………………………………………………… Correction ……………………..……………………………………………………………

9 7155/01/Computing/2020 Preliminary Exam For Examiner’s Use Error 3 ……………………………………………………………………………………… Correction ……………………..…………………………………………………………… Error 4 ……………………………………………………………………………………… Correction ……………………..…………………………………………………………… [8] (b) The algorithm does not include validation on input. (i) Name and describe one validation check that could be added to validate the input for the number of secondary one students. …………………………………………………………………………………... …………………………………………………………………………………... …………………………………………………………………………………... …………………………………………………………………………………... [2] (ii) Name one other different general validation check, other than your answer above. …………………………………………………………………………………... [1] (c) Software testing is important to verify that our program does what it is supposed to do. In your own words, describe why it is important to design good test cases. …………………………………………………………………………………………. …………………………………………………………………………………………. …………………………………………………………………………………………. [2]

10 7155/01/Computing/2020 Preliminary Exam For Examiner’s Use (d) In the following year, the school decided that the program should validate that weight should be at least 15kg. Identify two test conditions that should be used to test the algorithm for weight. For the condition, give an example of test data for this algorithm. Test conditions Test data [4] 9 A bank has the following spreadsheet, which shows the records of lump sum repayment loans taken out by its customers. (a) State the type of data that is held in each of the following cells. B4 ……………………………………………………………………………………. C4 ……………………………………………………………………………………. D4 ……………………………………………………………………………………. [3] (b) (i) In cell B16, the function gives the total of cells B4:B14. Identify the most appropriate function to use in this cell. …………………………………………………………………………………... [1]

11 7155/01/Computing/2020 Preliminary Exam For Examiner’s Use (ii) In cell B17, the formula shows the difference between the highest and the lowest Loan Pr