2021 NASS Computing P1

Name: .............................................................................. Register no: ............. Class: ................ NGEE ANN SECONDARY SCHOOL E PRELIMINARY EXAMINATION COMPUTING 7155/01 Paper 1 Written 20 September 2021 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. Answer ALL questions. Write in dark blue or black pen. You may use pencil for any diagrams, graphs, tables or rough working. The use of an approved scientific calculator is expected, where appropriate. 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 18 printed pages and 2 blank pages. For Examiner’s Use Total /80

2 NAS/2021/PRELIM/4E/COMPUTING(7155/01) 1 (a) Four terms of computer architecture and six descriptions are given. Draw one line from each term to its appropriate description. [4] Term Description Solid-state hard disk Optical disc Read-only memory Data that is stored is volatile and can be quickly accessed by the processor when needed. Data is stored on a magnetic material that can be read or written by a magnetic “head”. Data is stored as very small pits or indentations that can be read or written by a laser Data is stored in electronic circuits called “flash memory” that have no moving parts. Data that is stored rarely has need for change or would be needed for a computer to start up. Data is stored in a square plastic enclosure composed of a thin and flexible disk of a magnetic storage medium with a fabric that removes dust particles from the spinning disk Magnetic hard disk

3 NAS/2021/PRELIM/4E/COMPUTING(7155/01) 1 (b) The central processing unit acts like the “brain” of a computer system. It contains the circuitry to interpret and execute program instructions. Complete the following paragraphs by filling in the missing terms related to the central processing unit. The ………………………………………... does all mathematical operations and logical calculations. Some computers have two such units to process two calculations simultaneously. That is called dual core technology. These units are also accompanied by several small data storage units called ……………………………………….... . The ………………………………………. receives orders from ………………………………………... in the form of instruction and decode that instruction down into specific commands for other components inside computer system. It directs the data flow and how data should be stored, transmitted and received from different parts of the computer. [4]

4 NAS/2021/PRELIM/4E/COMPUTING(7155/01) 2 A game designing company plans to create a café simulation game, where the game character moves through different parts of the café and interacts with customers and equipment. • When the player chooses a new game, a character can be created along with its gender, name and appearance. • The appearance has an assortment of hair colours, eyes, nose, lips to be chosen from. • Each customer will order items form the café menu at random and will leave if not served within a time limit. • The game can also allow the player to shift furniture and equipment around the café. (a) Before writing the program, the game designers need to use modular decomposition to create smaller, more manageable modules of the game. One of these modules is the appearance. Identify four other modules that can be decomposed from the problem. Module 1 ……..……………………………………………………………………………… ...……………………..….……………………………………………………………………. Module 2 …………………..………………………………………………………………… ...………………………………..…………………………………………………………….. Module 3 …………………………..………………………………………………………… ...………………………………………..…………………………………………………….. Module 4 …………………………………..………………………………………………… ...………………………………………………..…………………………………………….. [4]

5 NAS/2021/PRELIM/4E/COMPUTING(7155/01) (b) The game designers wish to add a feature which can show the total amount of earnings made after each in-game day. Each item has its individual price and if customers are served within 30 seconds, an additional 20% of the item price would be added to the earnings. State the input(s), the output(s) and the process required to find the total earnings. Input(s): .…………………………..…………………………..……………………..……… …..……………………………………...……………………………..………………….….. Output(s): ….....………………………..…………………………..……………………..… ….…………………………………………………………………………………………….. Processes required: .….…………..…………………………..……………………........... ………....……………………………..…………………………..…………………………... ………....……………………………..…………………………..…………………………... ………....……………………………..…………………………..…………………………... ………....……………………………..…………………………..…………………………... [4]

6 NAS/2021/PRELIM/4E/COMPUTING(7155/01) (c) The name of the character can only be made up of alphabets and be between 3 to 15 characters, inclusive. The following pseudo-code algorithm validates the name of the character. 01 valid_name = False 02 WHILE valid_name = False 03 OUTPUT “Enter character name: ” 04 INPUT char_name 05 name_len = length(char_name) 06 IF name_len >= 3 AND name_len <= 15 07 valid_name = True 08 ENDIF 09 valid_name = alpha(char_name) // alpha()returns True if a string contains only alphabets, else 10 ENDWHILE (i) State whether valid_name is a variable of a constant. Give a reason for your choice. ……………………………………………………………………………………………. ………………………………………………………………………………………… [1] (ii) Identify the data validation techniques used in the algorithm. ………………………………………………………………………………………… [2] (iii) Once completed, the algorithm is tested with data for normal conditions. Identify two other test case conditions that could be used to test the algorithm. For each condition, give an example of test data for this algorithm Test case condition Test data [4]

7 NAS/2021/PRELIM/4E/COMPUTING(7155/01) 3 (a) Denary numbers are represented as binary numbers inside a computer. (i) Convert the denary number 105 into 8-bit binary. ………………………………………………………………………………………… [1] (ii) Convert the positive whole binary number 1101 0011 into a denary number. ………………………………………………………………………………………… [1] (b) Hexadecimal RGB codes represent colours. (i) The colour, baby-blue, has a hexadecimal code of 89CFF0. Complete the table to convert each hexadecimal digit to its 4-bit binary value. RGB code 8 9 C F F 0 4-bit binary …………. …………. …………. …………. …………. …………. [3] (ii) RGB colours have Red, Green and Blue values. The green value of one colour is 254 in denary. Convert 254 into hexadecimal. ………………………………………………………………………………………… [1] (iii) RGB colour codes are one example of where hexadecimal is used to represent binary. State two other examples where hexadecimal is used to represent binary. 1 ………………………………………………………………………………………….. 2 ………………………………………………………………………………………….. [2]

8 NAS/2021/PRELIM/4E/COMPUTING(7155/01) 4 Charles was working on his laptop when he saw the following message: The above message was received by many computers that experienced the WannaCry attack in May 2017. This cyberattack was known to be caused by a ransomware worm. (a) Describe what a worm is and explain how the cyberattack was carried out. ...………………………………………………………………………………………………. ...………………………………………………………………………………………………. ...………………………………………………………………………………………………. …..…………………………………………………………………………………………. [2] (b) Describe the impact of a ransomware attack on the user. ...………………………………………………………………