2021 SPS Computing P1 Solutions

[Turn over NAME CLASS INDEX NO. MARKING SCHEME ST. PATRICK'S SCHOOL PRELIMINARY EXAMINATION 2021 SUBJECT : Computing Paper 1 (7155/01) DATE : 23 August 2021 LEVEL : Secondary 4 Express DURATION : 2 hours INSTRUCTIONS TO CANDIDATES: Write your Name, Class and Index No. in the spaces at the top of this page. Write in dark blue or back pen. You may use a soft pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Answer all the questions. The use of an approved scientific calculator is expected, where appropriate. You are reminded of the need for clear presentation in your answers. The number of marks is given in brackets [ ] at the end of each question or part question. The total number of marks for this paper is 80. INFORMATION FOR CANDIDATES: The allocated marks for each question are indicated in the brackets [ ]. For Examiner’s Use Score /80 This question paper consists of 14 printed pages, including the cover page. 1 Five items of computer architecture and six descriptions are given. Candidates answer on the Question Paper.

2 Draw one line from each item to its appropriate description. Item Description Data bus Transfers required memory location from processor to memory; uni-directional Address bus Stores data, instructions and the results of processing for immediate use Secondary storage Extremely fast but small data storage spaces used directly by the ALU and control unit Memory Transfers data between memory and processor; bi-directional Processor register Stores large amounts of data that will not be lost when power supply is interrupted Processes data and follows instructions; consists of an arithmetic logic unit and a control unit [5]

3 [Turn over 2 A software company is creating an online learning portal for adult learners. (a) The user must first register an account in the portal. The user will then receive a verification email. Upon successful verification, the user can now login to the portal. In the portal, a registered user will be able to access the profile page where he/she can edit his/her personal information, email address, password and profile picture. The user can also access the courses page where he/she can view the details of the various courses available and select the courses that he/she wishes to enroll. Upon enrolling into a course, he/she can access the course materials and the portal will automatically track his/her learning progress. During the planning stage, the problem must be decomposed into smaller, more manageable parts called modules. Identify and describe two of these modules. 1 Registration module – describe the function 2 Courses module – describe the function. Any other valid answer. [2] (b) Another team in the company is responsible in creating a detective strategy game where the player assume the role of a detective. In one part of the game, the detective can access the files of the suspects. Identify two common elements between this game and the learning portal described in part (a). 1 Generalise the Course module for the implementation of the File Access module. 2 Generalise the Registration module for the implementation of the Player Registration module. [2]

4 3 Consider the following algorithm. 01 Ratio_1 = 0 02 Ratio_2 = 0 03 INPUT Bigger_Num 04 INPUT Smaller_Num 05 Ratio_1 = ROUND(Bigger_Num/Smaller_Num, 3) 06 Ratio_2 = ROUND((Bigger_Num + Smaller_Num)/Bigger_Num, 3) 07 IF Ratio_1 == Ratio_2 THEN 08 OUTPUT True 09 ELSE 09 OUTPUT False 09 ENDIF (a) Complete the following trace table for the algorithm. Use the data Bigger_Num = 61.84, Smaller_Num = 38.22 as input. Bigger_Num Smaller_Num Ratio_1 Ratio_2 OUTPUT 0 0 61.84 38.22 1.618 1.618 True [3] (b) The algorithm does not include validation on the inputs. Name and describe one validation check that could be added to validate the inputs. Format check or Presence check or Range check with the necessary description. e.g. format check on float data type. If non-float or non-integer data is entered, the program should display the appropriate error message to enter a float data type and ask the user to enter the correct data again. [2]

5 [Turn over (c) Decide on the data validation technique you would used in the algorithm and give a reason on your decision. Try again so that the user can enter the correct data without having to run the program from the start. [2] (d) For each of the following test case conditions, give one example of the test data that you would use to test the above algorithm. Normal Test Case Example of any integer or float test cases [1] Error Test Case Example of wrong data type [1] Boundary Test Case Division by 0 input or negative number, same numbers, incorrect range of number [1] 4 In general, there are five stages in developing a program. For each of the following stages, describe the goal of the stage and describe one task that can be done during that stage. Gather Requirements Stage Goal The goal of this initial stage is to determine the nature of the problem, why a program is needed and what the program is expected to do. If this stage is not performed properly, it is likely that any program that is developed will not actually solve the problem. Task - Interviewing the intended audience of the program to understand the nature of the problem or their expectations - Identifying the complete set of inputs that is necessary to define the problem and how the inputs can be supplied to the program being developed - Identifying the complete set of outputs that is necessary to solve the problem and the format for the output Plan Solutions Stage Goal The goal of this stage is to consider the options available before any code is written, and to choose an algorithm based on the resources available (such as manpower and time). Task - Manually solving different simplified examples of the problem and generalising the steps needed to produce the required output - Trying different ways to break down the problem into smaller parts such that the intended output of each part gets closer and closer to what is needed to solve the problem - Comparing the problem (or its smaller parts) to other problems that have been solved before and identifying which algorithms can be used - Estimating the amount of effort needed to write the code or the time needed to complete the algorithm before making a definite choice - Writing possible algorithms using either flowcharts or pseudo-code [4]

6 5 When we use a programming language, the source code must be translated into machine code before it can be run. Source code can be translated by a compiler or an interpreter. Describe one advantage that a compiler has over an interpreter and one advantage that an interpreter has over a compiler. Advantage of a compiler - The resulting program runs at a faster speed because all the translation has been done beforehand. - The compiler is not needed to run the program aftercompilation is complete. - Syntax errors are detected before the program is even run. Advantage of an interpreter - Changes to the source code take effect immediately. - Interpreters usually offer an interactive mode, which facilitates learning and experimentation. [2] 6 A new multinational company sets up its main headquarters in Country A and establishes another office in Country B. (a) State the type of network that would be suitable t