JYSS 4E COM Prelim P1 QP

JUNYUAN SECONDARY SCHOOL PRELIMINARY EXAMINATION 2022 SECONDARY FOUR EXPRESS CANDIDATE NAME CLASS INDEX NUMBER COMPUTING 7155/01 Paper 1 Written 26 Aug 2022 Candidates answer on the Question Paper. 2 hours No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your name, class and index number in the spaces at the top of this page. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. 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. This document consists of 14 printed pages and 2 blank pages. [Turn over For Examiner’s use 80

2 1 (a) The computer uses a complex circuit made of many components called the central processing unit (CPU). Two of these components are the ALU and CU. (i) State what ALU is and describe its function. [2] (ii) State what CU is and describe its function. [2] (b) Computers represent data using numbers that are express in different number systems. Show your working for the following questions. (i) Convert 12410 to a hexadecimal number. [2] (ii) Convert 11012 to a hexadecimal number. [2] (iii) Convert 17716 to a denary number. [2]

3 4E Computing P1 2022 Prelim [Turn over 2 Five terms of network systems and communications , and eight descriptions are given. Draw one line from each item to its appropriate description. Term Description Device that connects multiple LANs that uses the same protocol Media Access Control (MAC) address A 32-byte string that identifies a wireless access point (WAP) and all the devices connected to it. Server Used together with an Internet Protocol (IP) address to identify a program running on a network Port number Hardware interface to enable the transfer of data between a device and network Ethernet Computer that shares resources with and responds to requests on the network Network Interface Controller Sequence of bytes (usually permanent in nature) that is used to identify a particular physical network device. The most commonly used wired network protocol for local and metropolitan area networks. [5]

4 3 (a) In data transmission, packets are checked for errors using two different methods. One method is the parity check. (i) The data shown below uses an even parity system where the first digit is the parity bit. Fill in the missing bit. 0 1 1 1 0 1 1 [1] (ii) A checksum is a second error-checking method. Explain how a checksum detects errors. [3] (b) Jim plans to set up a new network system for his law firm with 50 staff working from the same office and 10 staff from remote locations such as their home or client’s office. The staff in the offic e share files and connect to printers and scanners. To protect their clients, data must be handled with high confidentiality. The new network system must be able to handle data from 10 years ago to the present. He plans to expand his firm in the next five years. (i) Suggest a suitable network topology. [1] (ii) Give two reasons why client-server network is more appropriate. 1 2 [2]

5 4E Computing P1 2022 Prelim [Turn over 4 There are many ways to prevent unauthorized access. encryption security tokens passwords privacy policy authenticated secret key firewall biometrics file permissions Insert five of the terms shown above in the correct spaces in the text below. Access control or authorization is the ability of a comput er to control the access of data and resources by a/an user. Below are three ways computers provide access control. Most operating systems can control the ability of users to view or make changes to specific files or folders by setting . However, these settings do not prevent unauthorized physical access to the storage device. To prevent this, it is necessary to use , which is the process of encoding data so that a/an is required to read the data. If the data is not decoded, it appears meaningless. Computers connected to a network require another layer of access control called a/an . This can be a device or a program that monitors every data transmission and prevents unauthorized access from a private network. [5]

6 5 (a) Spam is any kind of unwanted, uns olicited digital communication containing commercial messages that are sent out in bulk. Describe two measures that can be taken to reduce the impact of spam on email accounts. 1 2 [2] (b) Tick (  ) one or more boxes in each row to indicate the type of intellectual property violation for each scenario, if any, described in the table below. Scenario Copyright Infringement Plagiarism Alif installs a computer game on two different computers even though the licence he purchased allows for one installation only. Betty takes her friend’s artwork and submits it for a contest as her own artwork without her friend’s permission. Tao purchases an educational licence for a spreadsheet program and installs the program on his home laptop for school projects. [3]

7 4E Computing P1 2022 Prelim [Turn over 6 In a computer game, a character’s status during a mission depends on three variables: health, hydration and weapon. If any of the three conditions are met then the character dies, otherwise they are alive. The conditions are as follows:  Character has no more health or hydration.  Character has no weapon and health or hydration is less than 20.  All three of the variables are less than 10. If character is still alive, a subfunction WEAPON is called. 1 2 3 4 5 6 7 8 9 10 11 alive = True IF health == 0 or hydration == 0 THEN alive == True ELIF (health < 10 and weapon == 0) or (hydration < 10 and weapon == 0) THEN alive == False ELIF health < 10 or hydration < 10 or weapon < 10 THEN alive == False ELSE CALL WEAPON ENDIF (a) There are three logic errors in the pseudo-code. State the line number of each error and write the correct pseudo-code. Error 1 Correction Error 2 Correction Error 3 Correction [6] (b) What data type is the variable ‘alive’? [1] (c) Identify two other types of program error. 1 2 [2]

8 7 Study the following algorithm represented in pseudo-code. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 count = 0 sum = 0 INPUT number WHILE number >= 100 INPUT number ENDWHILE WHILE number >= 0 IF number % 2 == 0 THEN sum = sum + number count = count + 1 INPUT number WHILE number >= 100 INPUT number ENDWHILE ENDWHILE IF count != 0 THEN OUTPUT sum/count (a) Complete the trace table for the following set of data. 7, 12, 2, 4, 1, 6, 8 count sum number OUTPUT [4]

9 4E Computing P1 2022 Prelim [Turn over (b) State the purpose of the algorithm. [2] (c) What happens if a negative number was the first data input?