Cambridge IGCSE Computer Studies 0420 — 2013 May/June Paper 1 · Variant 1

This document consists of 20 printed pages. IB13 06_0420_11/3RP © UCLES 2013 [Turn over *7633507456* For Examiner's Use UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS International General Certificate of Secondary Education COMPUTER STUDIES 0420/11 Paper 1 May/June 2013 2 hours 30 minutes Candidates answer on the Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your Centre number, candidate number and name on all the work you hand in. Write in dark blue or black pen. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. Answer all questions. No marks will be awarded for using brand names of software packages or hardware. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. www.XtremePapers.com

2 © UCLES 2013 0420/11/M/J/13 For Examiner's Use 1 Name a suitable sensor for each of the following applications. Choose a different sensor in each application. (i) control of a central heating system (ii) operation of automatic doors (iii) detection of intruders (iv) monitoring of a greenhouse environment [4] 2 Name two different types of loop structure in a typical programming language. Give an example of how ten numbers could be input using the named loop. Name of type of loop structure Example Name of type of loop structure Example [6]

3 © UCLES 2013 0420/11/M/J/13 [Turn over For Examiner's Use 3 (a) Which of the following activities should always be regarded as security risks to computer systems? Indicate by ticking (
) the Yes or No column. Activity Yes No chat rooms cookies pharming virus VoIP [2] (b) State what is meant by the five computer terms in the table. chat rooms cookies pharming virus VoIP [5]

4 © UCLES 2013 0420/11/M/J/13 For Examiner's Use 4 (a) Name the following types of network topologies: (i) (ii) [2] (b) Give one benefit and one drawback of networking computers. Benefit Drawback [2] (c) Many networks are known as LAN or WAN. Give one feature of each type of network. LAN WAN [2]

5 © UCLES 2013 0420/11/M/J/13 [Turn over For Examiner's Use 5 Name a suitable hardware device to enable automatic data capture in each of the following applications. Each device must be different. Application Hardware device automatic stock control system in a supermarket keeping track of the livestock on a large farm input data into a computer using speech recognition [3]

6 © UCLES 2013 0420/11/M/J/13 For Examiner's Use 6 Animation using computer systems involves many stages. The diagram below shows a number of descriptions and terms used in computer animation. By drawing arrows, connect the correct description to the animation term. generating intermediate frames between two images to give the appearance of movement morphing special effect that changes one image into another image (for example, the special effect of a person slowly turning into an animal) rendering generating a final completed 3D image from a given 2D model by the use of software tweening very simple drawing made up of lines, circles and dots used to depict a character (for example, a human being) key frames a variable controlling the position of part of an animated character (for example, to control the changes in a facial expression) stick figure drawings that define the starting point and end point of any smooth transition in animation avar [5]

7 © UCLES 2013 0420/11/M/J/13 [Turn over For Examiner's Use 7 Which five computer terms are being described below? (i) typing in the same data twice and the computer checks both sets of data to see if they exactly match (ii) signal sent from a printer requesting attention from the processor; this causes a temporary break in the execution of whatever the processor is doing (iii) exchange of signals between two devices to ensure synchronisation when communication starts (iv) temporary storage area in a printer that holds data waiting to be printed (v) count of the number of bits before transmission which is sent with the transmission so that the receiver can check to see whether the same number of bits have arrived [5]

8 © UCLES 2013 0420/11/M/J/13 For Examiner's Use 8 A company has set up a website to advertise and show houses for sale. A customer can get access to an online interactive map and can also take a tour around the house. (a) Describe three features you would expect to see on an interactive map. 1 2 3 [3] (b) (i) Name the type of computer technology that enables a tour of the house to take place using a website. [1] (ii) What three features would you expect to see on the website which allows a customer to take this tour? 1 2 3 [3]

9 © UCLES 2013 0420/11/M/J/13 [Turn over For Examiner's Use 9 An expert system has been set up to help diagnose faults in car engine management systems. (a) One component is an interactive user interface. Name three other components in a typical expert system. 1 2 3 [3] (b) Identify two of the features you would expect to see in a typical interactive user interface supplied with an expert system. 1 2 [2]

10 © UCLES 2013 0420/11/M/J/13 For Examiner's Use 10 (a) (i) Complete the truth table for the logic circuit which is made up of NAND gates only. A B X A B Working space X 0 0 0 1 1 0 1 1 [2] (ii) What single logic gate has the same function as the above logic circuit? [1]

11 © UCLES 2013 0420/11/M/J/13 [Turn over For Examiner's Use (b) (i) Complete the truth table for the logic circuit. A B C AND AND OR OR X 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] (ii) What could replace the whole logic circuit? [1]

12 © UCLES 2013 0420/11/M/J/13 For Examiner's Use 11 Letters from the Greek alphabet are to be transferred to a computer system. Each letter can be represented on an 8 by 8 grid. Each column has a value from 1 to 128. The value of each row is stored in a table. The values in the column headings are used to work out the value for each row (e.g. in our example, row 8 has the value 64 + 32 + 4 + 2 = 102). Thus, in the example below, the letter (π) is stored as: row 1 2 3 4 5 6 7 8 value 255 255 102 102 102 102 102 102 128 64 32 16 8 4 2 1 (a) What values would be stored in the table for the Greek character (Σ)? row 1 2 3 4 5 6 7 8 value 128 64 32 16 8 4 2 1 [4] (b) Draw the character formed from the following value table: row 1 2 3 4 5 6 7 8 value 146 146 84 84 56 16 16 16 128 64 32 16 8 4 2 1 [4]

13 © UCLES 2013 0420/11/M/J/13 [Turn over For Examiner's Use 12 A database was set up to compare oil companies. A section of the database is shown below: Code Name of company No of employees No of countries Head office Profits (billion $) Share price ($) AR Arrows 60 000 30 Americas 8.0 39.00 GZ Gazjeti 35 000 4 Asia 5.0 44.50 KO Konoco 40 000 22 Americas 10.0 18.55 OS Oilbras 56 000 11 Americas 4.0 59.60 SD Sand Oil 102 000 51 Europe 12.0 15.30 SN Southern Oil 50 000 15 Americas 11.0 10.90 ST Static Oil 80 000 31 Americas 10.0 52.05 SU Summation 70 000 40 Europe 9.0 30.40 WP Wasp Petrol 90 000 44 Europe 15.0 92.80 (a) How many fields are there in each record? [1] (b) The following search condition was entered: (No of countries < 30) AND (Head office = “Americas”) Using Code only, which records would be output? [2] (c) What search condition is needed to find out which oil companies have a share price less than $50 or whose profits were greater than 8 billion dollars? [2]

14 © UCLES 2013 0420/11/M/J/13 For Examiner's Use 13 A customer uses Internet banking. To gain access to their account they need: • an 8-digit ID • a 4-digit PIN • a 10-character password They will be asked to type in their ID, then 3 digits from their PIN and finally 3 characters from their password. Three attempts at the ID are allowed, but only one attempt at the PIN and at the password. The flowchart on the next page shows the access process described above. However, most of the stages have been omitted. Complete the flowchart, using item number only, from the list of items given. Item number Item description 1 access to account allowed 2 are any characters in the password incorrect? 3 are any digits in the ID incorrect? 4 are any digits in the PIN incorrect? 5 generate three random digits from the PIN 6 generate three random characters from the password 7 input the required three digits from the PIN 8 is number of digits < 8 or number of digits > 8? 9 is X > 2? 10 output “access to account denied” 11 X = X + 1

15 © UCLES 2013 0420/11/M/J/13 [Turn over For Examiner's Use START END X = 0 INPUT 8-digit ID INPUT 3 characters from password END No No No No No Yes Yes Yes Yes Yes [6]

16 © UCLES 2013 0420/11/M/J/13 For Examiner's Use 14 An aeroplane uses three separate computer systems to monitor and control the flight process while in auto pilot mode. (a) Explain the advantages of using three computers rather than just one. [2] (b) Sensors are used to measure air speed. The readings are sent to the three computers. Describe how the sensors and computers are used to control the aeroplane’s speed in auto pilot mode. [4]

17 © UCLES 2013 0420/11/M/J/13 [Turn over For Examiner's Use (c) The aeroplane uses GPS (global positioning system) technology to navigate to its destination. (i) How does GPS link with the computers to ensure the correct flight path (for example, direction) is maintained? [3] (ii) Give one benefit and one drawback of using GPS. benefit drawback [2]

18 © UCLES 2013 0420/11/M/J/13 For Examiner's Use 15 A spreadsheet was set up to allow customers to work out their monthly payments when borrowing money from a bank. The customer inputs data in column B. The spreadsheet is as follows: A B C 1 Interest Calculator 2 INPUT PRICE OF GOODS 20 000 3 INPUT YOUR DEPOSIT 5 000 4 AMOUNT OF MONEY TO BORROW 15 000 5 INPUT % INTEREST RATE 8.0 0.08 6 INPUT NUMBER OF YEARS 4 7 INTEREST TO PAY 4800 8 YOUR MONTHLY REPAYMENTS 412.50 (a) Cell C4 contains the amount of money to borrow. What formula must be in cell C4? = [1] (b) Cell C5 contains the % interest rate as a decimal (for example, 8% shows as 0.08). What formula must be in cell C5? = [1] (c) Cell C7 contains interest to pay which is found from amount of money borrowed × interest rate as a decimal × number of years. What formula must be in cell C7? = [1] (d) Cell C8 contains the monthly repayment which is found from sum of the amount borrowed and interest to pay divided by total number of months. What formula must be in cell C8? = [2]

19 © UCLES 2013 0420/11/M/J/13 [Turn over For Examiner's Use (e) Give two different validation checks you would use for inputs to cells: B2 B5 [2] (f) Describe how you would test the spreadsheet to ensure it works correctly. [2]

20 Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every reasonable effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the publisher will be pleased to make amends at the earliest possible opportunity. University of Cambridge International Examinations is part of the Cambridge Assessment Group. Cambridge Assessment is the brand name of University of Cambridge Local Examinations Syndicate (UCLES), which is itself a department of the University of Cambridge. © UCLES 2013 0420/11/M/J/13 For Examiner's Use 16 A small shop uses barcodes which represent 5 digits. The last digit is used as a check digit. For example: a b c d e 0 1 2 3 4 The check digit (e) is found by: • multiplying the first and third digits (i.e. a and c) by 3 • multiplying the second and fourth digits (i.e. b and d) by 2 • adding these four results together to give a total • dividing this total by 10 • remainder is check digit (e) Write an algorithm, using pseudocode or flowchart only, which • inputs 100 five-digit barcodes in the form a, b, c, d, e • re-calculates the check digit for each number and checks whether the input check digit (e) is correct • outputs the number of barcodes which were entered correctly [5]

CAMBRIDGE INTERNATIONAL EXAMINATIONS International General Certificate of Secondary Education MARK SCHEME for the May/June 2013 series 0420 COMPUTER STUDIES 0420/11 Paper 1, maximum raw mark 100 This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began, which would have considered the acceptability of alternative answers. Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the May/June 2013 series for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level components and some Ordinary Level components. www.XtremePapers.com

Page 2 Mark Scheme Syllabus Paper IGCSE – May/June 2013 0420 11 © Cambridge International Examinations 2013 1 A different sensor is needed for each application (i) central heating system – temperature sensor (ii) automatic doors – pressure sensor/pad – light sensor – infra red sensor (iii) detection of intruders – pressure sensor/pad – light sensor – infra red sensor – sound/acoustic sensor (iv) greenhouse monitoring – temperature sensor – moisture/humidity sensor – light sensor – pH sensor – CO2/O2 (levels) sensor [4] 2 1 mark for name of loop structure + 1 mark for correct loop structure including initialisation + 1 mark for correct input inside loop: for (… to … next) loop example: for x = 1 to 10 input number next x repeat (… until) loop example: c = 0 repeat input number c = c + 1 until c > 9 (or equivalent) while (… endwhile/wend) loop example: c = 0 while c <> 10 do input number c = c + 1 endwhile [6]

Page 3 Mark Scheme Syllabus Paper IGCSE – May/June 2013 0420 11 © Cambridge International Examinations 2013 (3) (a) 2 marks minus 1 for each error. activity Yes No chat rooms
cookies
pharming
virus
VoIP
[2] (b) 1 mark per description chat rooms – place for online conversations – use instant messaging – to allow communications in real time – users register and choose user name and password – log onto enter chat room using user name and password – list of people currently in room will be alerted as soon as new person enters room cookies – small files sent to user’s computer when visiting a website – stores information about user which is accessed every time user visits that website – lets website know who you are/past visitor pharming – malicious code installed on a user’s computer/web server – misdirecting the user(s) to a bogus/fake fraudulent website – can use domain name poisoning virus – programs that replicate themselves – designed to disrupt computer system – delete/alter/corrupt files VoIP – Voice over Internet Protocol – system that allows user to talk to another user using the Internet – can use USB phone or head set (microphone and headphones) – requires fast broadband connection to work – can also combine with webcam and instant messaging [5]

Page 4 Mark Scheme Syllabus Paper IGCSE – May/June 2013 0420 11 © Cambridge International Examinations 2013 (4) (a) (i) ring [1] (ii) star [1] (b) 1 mark for benefit and 1 mark for drawback benefit – share resources such as hardware e.g. printer, software – easier to monitor what users are doing – easier communication between users drawback – greater risk of viruses – greater security risk (such as hacking) – expensive hardware such as servers, cabling, … – needs management [2] (c) 1 mark for LAN feature and 1 mark for WAN feature LAN – used over a small geographic area (e.g. one building) – doesn’t require external telecommunication WAN – used over remote/vast geographic area (e.g. continents) – needs modem, external phone lines, microwaves… [2] 5 1 mark for each correct device application hardware device automatic stock control system in a supermarket barcode reader/scanner/EFTPOS terminal keeping track of the live stock on a large farm barcode/RFID/microchip reader input data into a computer using speech recognition microphone [3]

Page 5 Mark Scheme Syllabus Paper IGCSE – May/June 2013 0420 11 © Cambridge International Examinations 2013 6 [5] generating intermediate frames between two images to give the appearance of movement special effect that changes one image into another image (e.g. the special effect of a person slowly turning into an alien) generating a final completed 3D image from a given 2D model by the use of software variable controlling the position of part of an animated character (e.g. control changes in a facial expression) drawings that define the starting point and end point of any smooth transition in animation very simple drawing made up of lines, circles and dots used to depict a character (e.g. a human being) morphing rendering tweening key frames stick figure avar

Page 6 Mark Scheme Syllabus Paper IGCSE – May/June 2013 0420 11 © Cambridge International Examinations 2013 7 1 mark for each correct term. (i) verification [1] (ii) interrupt [1] (iii) handshaking [1] (iv) (printer) buffer, RAM [1] (v) checksum [1] (8) (a) Any three features from: – road map and satellite views – superimpose road map and satellite images – ability to zoom in and zoom out – arrow keys to move N, S, E and W – detailed directions to get from customer’s home to the house – ability to use street name, post code, zip code (etc.) in searches – “pins” to show exact location of house on the map/hotspot – local amenities e.g. post office, school etc. – scale/conversion of miles to kilometres [3] (b) (i) virtual reality [1] (ii) Any three from: – zoom in and out – buttons to navigate between rooms/enter the tour – arrow keys to rotate through 360º – print out of rooms – save houses visited as “favourites” – choice of area within house to view [3] (9) (a) Any three from: – knowledge base – inference engine – rule(s) base – (expert system) shell – explanation system [3] (b) Any two from: – yes/no type of questions – multiple choice questions – explanations/examples [2]

Page 7 Mark Scheme Syllabus Paper IGCSE – May/June 2013 0420 11 © Cambridge International Examinations 2013 10 (a) (i) A B X 0 0 1 0 1 0 1 0 0 1 1 0 [2] (ii) NOR gate (allow follow through from part (i)) [1] (b) (i) A B C X 0 0 0 0 0 0 1 1 0 1 0 0 0 1 1 1 1 0 0 0 1 0 1 1 1 1 0 0 1 1 1 1 [4] (ii) input C only [1] 11 (a) row value 1 255 2 192 3 96 4 48 5 96 6 192 7 255 8 0 [4] (b) 128 64 32 16 8 4 2 1 [4] } } 1 mark 1 mark } } } } 1 mark 1 mark 1 mark 1 mark } } } } 1 mark 1 mark 1 mark 1 mark } } } } 1 mark 1 mark 1 mark 1 mark

Page 8 Mark Scheme Syllabus Paper IGCSE – May/June 2013 0420 11 © Cambridge International Examinations 2013 12 (a) 7 [1] (b) KO, OS, SN (–1 mark for each error) [2] (c) (Share price ($) < 50.00) OR (Profits (billion $) > 8.0) < - - - - - (1 mark) - - - - -> < - - - - - - - (1 mark) - - - - - - - > (Profits (billion $) > 8.0) OR (Share price ($) < 50.00) < - - - - - (1 mark) - - - - > < - - - - - - - (1 mark) - - - - - - - > [2]

Page 9 Mark Scheme Syllabus Paper IGCSE – May/June 2013 0420 11 © Cambridge International Examinations 2013 13 START X = 0 INPUT 8- digit id 9 8/3 3/8 11 10 END 5 7 4 6 INPUT 3 characters from password 2 1 END Yes No Yes No Yes No Yes No Yes No 1 mark 1 mark 1 mark 1 mark 1 mark [6] 1 mark

Page 10 Mark Scheme Syllabus Paper IGCSE – May/June 2013 0420 11 © Cambridge International Examinations 2013 14 (a) Any two from: – if all computers ‘agree’ system works automatically – if one computer fails, there are still 2 working – if one computer is faulty, use “majority output” to make decisions – increases passenger confidence in the system [2] (b) Any four points from: – sensor readings are taken (continuously) – these are converted to digital (using ADC) – data/signals sent to the computer – the computer compares the data received with stored values/computer interprets signals – if outside acceptable range, computer sends signals – signals converted to analogue (using DAC) – fuel to engines is increased/decreased to control aeroplane speed – if one computer gives a different signal, a warning message is sent [4] (c) (i) Any three points from: – satellite sends/broadcasts signals to earth – GPS system uses satellite signals to calculate position of aeroplane – …..data from at least three satellites needed to calculate this position – satellites use atomic clocks to ensure very accurate timing – each satellite transmits data giving its position and time – computer compares calculated position supplied by GPS system with flight path … – … if aeroplane off course, then computer sends signals … – … and rudder settings are changed (using motors) to control direction – if aeroplane is on course, no action is taken – direction checking is carried out continuously [3] (ii) 1 mark for benefit and 1 mark for drawback benefit – estimate time of arrival at destination/remaining flight time – location of alternative airports in case of emergency – more accurate flight path maintained – more efficient fuel costs since fewer course corrections are made drawback – if weather is bad, GPS and computer won’t automatically “steer around the problem” – loss of satellite signal could lead to wrong direction/decision making [2]

Page 11 Mark Scheme Syllabus Paper IGCSE – May/June 2013 0420 11 © Cambridge International Examinations 2013 15 (a) B2 – B3 [1] (b) B5/100 or B5*1% [1] (c) C4 * C5 * B6 [1] (d) (C4 + C7) / (B6 * 12) < 1 mark > < 1 mark > [2] (e) B2 – check for negative numbers – check for numbers only (character/type check) – presence check – range check B5 – range check – character/type check – presence check (validation checks must be DIFFERENT for each part of question) [2] (f) Any two points from: – input data with known results – compare output with known results – use data to check if validation rules work – use of normal and abnormal and extreme data – check deposit < price [2]

Page 12 Mark Scheme Syllabus Paper IGCSE – May/June 2013 0420 11 © Cambridge International Examinations 2013 16 marking points: – set total of barcodes entered correctly to zero (initialisation, e.g. match = 0 below) 1 mark – input 100 numbers (correct loop structure) 1 mark – input 5 digits of the barcode (a, b, c, d and e) INSIDE a loop 1 mark – find total value using barcode formula given 1 mark – method for finding remainder 2 marks (e.g. subtract 10 from total (1 mark) using a loop (1 mark) until total < 10) – finding out how many correct barcodes were input 1 mark – correct output (OUTSIDE loop – must have a loop to get mark) 1 mark example of suitable coding: match = 0 1 mark for number = 1 to 100 1 mark input a, b, c, d, e 1 mark total = (a * 3) + (c * 3) + (b * 2) + (d * 2) 1 mark repeat total = total – 10 2 marks until total < 10 if total = e then match = match + 1 1 mark next number print match 1 mark [5]