BVSS 2020 P1

2 1 Computer parts can be organised into roles. Match each role to its description. Role Description Address bus • • Intermediate or final results produced by the computer; usually in the form of processed data. Memory • • Processes data and follows instructions; consists of an arithmetic logic unit and a control unit. Output • • Stores data, instructions and the results of processing for immediate use. Processor • • Stores large amounts of data that will not be lost when power supply is interrupted. Secondary storage • • Transports data between memory and processor; bi-directional. • Transports required memory location from processor to memory; uni-directional. [5] 2 (a) Name one type of external storage. ............................................................................................................ [1]

3 (b) Describe one advantage and one disadvantage of using the type of external storage in Part (a). Advantage: …………………………………………………………………… ………………………………………………………………………………..... ………………………………………………………………………………..... Disadvantage: ……………………………………………………………...... ………………………………………………………………………………..... ………………………………………………………………………………..... [2] 3 A meteorologist wants to determine the date of the day with the lowest amount of rainfall in a certain month for a particular year. State the input, output and process needed to solve the problem. Assume that there are 30 days in that month. Input: ………………………………………………………………………………...... ………………………………………………………………………………………..... ………………………………………………………………………………………..... Output: ………………………………………………………………………………… ………………………………………………………………………………………..... ………………………………………………………………………………………..... Process: ………………………………………………………………………………. ………………………………………………………………………………………..... ………………………………………………………………………………………..... ………………………………………………………………………………………..... ………………………………………………………………………………………..... [5]

4 4 Fill in the blanks using the words provided. algorithm decomposition flowchart generalisation incremental modular pattern recognition Problem solving techniques are essential in simplifying complex problems. The first technique involves breaking down a complex problem into sub- problems. This is called ........................................ For this, there are two approaches. The ........................................ approach involves deriving a solution to a smaller version of the problem then extending the solution to larger versions of the problem. The ........................................ approach involves separating tasks into distinct sub-problems. The second technique involves identifying similarities among items. This is called ........................................ The third technique involves replacing similar problems with a single problem. This is called ......................................... [5]

5 5 Predict the expected output of the following Python program. (a) word_A = "INTERNATIONAL" print(word_A[5:8]) ............................................................................................................ [1] (b) word_B = "SINGAPORE" print(word_B[3:8:2]) ............................................................................................................ [1] (c) word_C = "BUKIT BATOK" print(word_C[2::3]) ............................................................................................................ [1] (d) my_input = "BVSS" print(my_input.isalnum()) ............................................................................................................ [1] (e) word_D = "hello" word_E = "world" print(word_D + " " + word_E.upper()) ............................................................................................................ [1]

6 6 Study the following algorithm represented in pseudo-code. Number = 50 Tries = 5 Won = False WHILE Tries > 0 INPUT Guess Tries = Tries - 1 IF Guess > Number OUTPUT "Guess lower" ELSE IF Guess < Number OUTPUT "Guess higher" ELSE Won = True Tries = 0 ENDIF ENDIF ENDWHILE IF Won = False OUTPUT "Game over" ELSE OUTPUT "You win" (a) Complete the following trace table for the algorithm. Use the data 25, 75, 50 as input. Number Tries Won Guess OUTPUT

7 [5] (b) State the purpose of the algorithm. ………………………………………………………………………………..... ………………………………………………………………………………..... ............................................................................................................ [1] (c) Name and describe two validation checks that can be added to validate the input. Validation check 1: …………………………………………………………... ………………………………………………………………………………..... ………………………………………………………………………………..... Validation check 2: …………………………………………………………... ………………………………………………………………………………..... ………………………………………………………………………………..... [4] 7 Describe the difference between a compiler and an interpreter. ………………………………………………………………………………………..... ………………………………………………………………………………………..... ……………………………………………………………………………………… [2]

8 8 The following pseudo-code algorithm prompts students to enter the category of their CCA (i.e. 1 for uniformed groups, 2 for performing arts, etc.). When 5 is entered, the program outputs the abbreviation of the most popular category and terminates. The program uses two arrays. The array cca_categories stores the abbreviations of the categories. The array cca_counter stores the number of entries per category. For simplicity, you may assume that all entries are valid and that the number of entries per category are unique. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 cca_categories = ["UG", "PA", "CS", "GS"] cca_counter = [0] * 4 exit_program = FALSE highest_count = 0 highest_count_index = 0 OUTPUT "Enter 1 for Uniformed Groups (UG)" OUTPUT "Enter 2 for Performing Arts (PA)" OUTPUT "Enter 3 for Clubs and Societies (CS)" OUTPUT "Enter 4 for Games and Sports (GS)" OUTPUT "Enter 5 to exit program" WHILE exit_program = TRUE INPUT my_cca IF my_cca = 5 exit_program = TRUE ELSE cca_counter[my_cca - 1] += 2 ENDIF ENDWHILE FOR i = 0 TO 3 IF cca_counter[i] < highest_count highest_count = cca_counter[i] highest_count_index = highest_count ENDIF NEXT i INPUT cca_categories[highest_count_index] There are five errors in the program. For each error, state the number of the line where the error is located and correct the error. Line: …………………………………………………………………………………… Correction: ……………………………………………………………………………. Line: …………………………………………………………………………………… Correction: ……………………………………………………………………………. Line: …………………………………………………………………………………… Correction: …………………………………………………………………………….

9 Line: …………………………………………………………………………………… Correction: ……………………………………………………………………………. Line: …………………………………………………………………………………… Correction: ……………………………………………………………………………. [5] 9 (a) Describe how phishing works and state two tell-tale signs of a phishing attack. ………………………………………………………………………………..... ………………………………………………………………………………..... ………………………………………………………………………………..... ………………………………………………………………………………..... ............................................................................................................ [3] (b) Besides phishing, name one other type of cyberattack. ............................................................................................................ [1] 10 (a) Convert the denary number 155 into 8-bit binary. Show your working clearly. ………………………………………………………………………………..... ………………………………………………………………………………..... ………………………………………………………………………………..... ………………………………………………………………………………..... ............................................................................................................ [2]

10 (b) Convert the binary number 00111100 into