NASS 2020 P1

Name: .............................................................................. Register no: .............. Class: ...... NGEE ANN SECONDARY SCHOOL O PRELIMINARY EXAMINATION COMPUTING 7155/01 Paper 1 Written 20 August 2020 2 hours Candidates answer on the Question Paper. No Additional Materials are required. Instructions to Candidates Write your name, register number and class at the top of this page. Write in dark blue or black pen. You may use an HB pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, glue or correction fluid. Approved calculators are allowed. Answer all questions. 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. Checked by student: _____________________ Date: _________ This document consists of 16 printed pages and 0 blank pages. For Examiner’s Use Marks /80

2 NAS/2020/Prelim/4E/7155/01 1 (a) Convert the following amounts of data in the table below: Amount of data Size in bytes 2.4 MB 5 × 10243 [1] [1] (b) James is setting up his home computer for work. He is considering between buying a 900 MHz processor chip and a 3 GHz processor chip. Describe 2 differences between the processor chips that he will need to consider before deciding which processor chip to purchase. …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… [2] (c) Fill in the blanks below with an appropriate word/phrase. [4] The following data flow may occur when input or output devices are used. Data is entered using an ________________ device and converted into a form that the computer can understand. This data may be temporarily stored in a __________________________________. Instructions from the running application are then interpreted. These instructions involving logical operations may require the data to be processed by the processor’s ________________________________. The _______________________ may then redirect the processed data to an output device for display in a form that users can understand.

3 NAS/2020/Prelim/4E/7155/01 2 (a) State the difference between a proprietary software and a free and open-source software (FOSS). …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… [2] (b) A secondary two student requires materials from the Internet for a project report. Suggest two guidelines he should take note of to avoid committing copyright infringement. …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… [2] 3 The Covid-19 pandemic has impacted various aspects of people’s lives greatly. (a) Lockdowns and tightened measures around the world has caused restrictions to people’s social lives. Describe the positive and negative social impact brought about by advancements in technology during this period. …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… [2]

4 NAS/2020/Prelim/4E/7155/01 (b) Some essential services such as banking operations are temporarily disrupted as a result of a tightened measure to minimize crowding. This also give rise to scams known as “SMiShing”. SMiShing is a phishing attack through the use of text messages. An example is shown below: Suggest two tell-tale signs that show that it could potentially be a SMiShing message. …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… [2]

5 NAS/2020/Prelim/4E/7155/01 4 The following spreadsheet shows a customer’s car loan details with ABC company. In this car loan scheme, the customer pays a down payment and takes a loan for the remaining amount. The customer takes a loan and pays monthly instalments over 1.5 years. The interest charged on the loan is compounded monthly. (a) State the type of data that is held in each of the following cells. B3: ____________________________ [1] B5: ____________________________ [1]

6 NAS/2020/Prelim/4E/7155/01 (b) The cell B9 shows the monthly instalment amount in this loan scheme. Identify the most appropriate formula to use in cell B9. …………………………………………………………………………………………… [1] (c) The cell B29 shows the principal payment in the 18th month of this scheme. Identify the most appropriate formula to use in cell B29. …………………………………………………………………………………………… [1] (d) The cell C12 shows the interest payment in the 1st month of this scheme. Identify the most appropriate formula to use in cell C12. …………………………………………………………………………………………… [1] (e) The cells C12 – C29 show the interest payments over the 18 months of this scheme. Explain how the background of the cells containing less than $50 can be highlighted in red. …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… [2]

7 NAS/2020/Prelim/4E/7155/01 5 (a) Identify the logic gate represented by the following truth table. A B X 0 0 1 0 1 1 1 0 1 1 1 0 …………………………………………………………………………………………… [1] (b) Draw the logic circuit to represent the following Boolean statement. Do not simplify the statement. X = A NAND ((A NOR B) OR (B AND (NOT C))) [5]

8 NAS/2020/Prelim/4E/7155/01 (c) Complete the truth table for the Boolean statement: X = A NAND ((A NOR B) OR (B AND (NOT C))) A B C 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] 6 An electronic guessing game compares denary integer values input by a user with pre-stored values. The pre-stored values are held in 10-bit binary format. (a) Convert the binary values in the table to denary. Binary Denary 0001001110 0110110111 1000000001 [3]

9 NAS/2020/Prelim/4E/7155/01 (b) Describe how the binary value 0110110111 is converted into hexadecimal. Give the hexadecimal value in your answer. Description …………………………………………………………………………….. …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… Hexadecimal value ……………………………………………………………………. [4] (c) When planning the game, the designer decided to use hexadecimal number system to represent the binary values. Explain why the designer used the hexadecimal number system. …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… [2] (d) Besides game design, state another example where hexadecimal is used to represent binary. …………………………………………………………………………………………… [1]

10 NAS/2020/Prelim/4E/7155/01 7 The following diagram shows four network terms and six descriptions. Draw a line between the term and the correct description. [4] Term Description Ethernet Media Access Control (MAC) Wireless access point (WAP