Cambridge IGCSE Computer Studies 0420 — 2012 May/June Paper 1 · Variant 3

This document consists of 21 printed pages and 3 blank pages. IB12 06_0420_13/FP © UCLES 2012 [Turn over *2907193166* For Examiner's Use UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS International General Certificate of Secondary Education COMPUTER STUDIES 0420/13 Paper 1 May/June 2012 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 2012 0420/13/M/J/12 For Examiner's Use 1 Video conferencing, Voice over Internet Protocol (VoIP) and instant messaging are all used as communication methods. Certain devices are essential to enable each of these communication methods to be used. Tick (
) the appropriate cells in the table below to show which one or more devices are essential for each method. keyboard microphone speaker webcam VoIP video conferencing instant messaging [3] 2 Describe ways to guard against each of the following Internet security issues. (A different method should be given in each case.) viruses hacking spyware phishing tapping into wireless networks [5]

3 © UCLES 2012 0420/13/M/J/12 [Turn over For Examiner's Use 3 An airport is converting all its manual information systems to computerised systems. (a) One stage in analysing the existing system is fact finding. State three methods of fact finding: 1 2 3 [3] (b) Which of your named methods would be best suited to this application? Give two reasons for your choice. Method Reason 1 Reason 2 [2] 4 Michael is preparing a multimedia presentation. (a) What three features should he include in his presentation to make it more interesting? 1 2 3 [3] (b) Give two reasons why a presentation would be better than just printing out and distributing a newsletter. 1 2 [2]

4 © UCLES 2012 0420/13/M/J/12 For Examiner's Use 5 A floor turtle can use the following instructions. Instruction Meaning FORWARD x Move x cm forwards LEFT t Turn left t degrees RIGHT t Turn right t degrees REPEAT n Repeat next set of instructions n times ENDREPEAT Finish repeated instructions PENUP Lift the pen PENDOWN Lower the pen 45° 45° Start Finish Each square = 10 cm by 10 cm Each diagonal line = 14 cm

5 © UCLES 2012 0420/13/M/J/12 [Turn over For Examiner's Use Complete the set of instructions to draw the above shape in the direction shown by the arrows. PENDOWN FORWARD 20 LEFT 90 [5]

6 © UCLES 2012 0420/13/M/J/12 For Examiner's Use 6 Carefully study the following flowchart. START STOP C = 1 L = 0 N = 0 S = 0 T = 0 Is A > B ? L = L + 1 N = A – B N = 0 Is B > A ? Is C < = 10 ? No T = T + N C = C + 1 No Yes INPUT A, B OUTPUT L, S, T Yes S = S + 1 N = B – A Yes No

7 © UCLES 2012 0420/13/M/J/12 [Turn over For Examiner's Use (a) Complete the trace table for the following data: 8, 4, 3, 1, 5, 8, 4, 2, 1, 3, 2, 2, 1, 2, 5, 5, 4, 0, 5, 4 C L N S T A B [6] (b) What is the final output from the algorithm? L = S = T = [2]

8 © UCLES 2012 0420/13/M/J/12 For Examiner's Use 7 A large hotel has a website. The website offers the following facilities: • a virtual tour of the hotel • an interactive map • the ability to book rooms online (a) Give two features you would expect to find in each facility. virtual tour 1 2 interactive map 1 2 room booking online 1 2 [6] (b) Describe one other feature you would expect to see on the hotel’s website. [1]

9 © UCLES 2012 0420/13/M/J/12 [Turn over For Examiner's Use 8 A spreadsheet has been set up to record employees’ hotel expenses for one year. The data for one employee is shown below. A B C D E F G 1 Hotel Tariff Sunday to Thursday ($) Tariff Friday to Saturday ($) No of nights (Sunday to Thursday) No of nights (Friday to Saturday) Total cost ($) Maximum allowance ($) 2 Grand 150 90 3 2 630 600 3 Station 200 120 2 1 520 800 4 Northern 90 60 5 0 450 360 5 Western 120 80 4 1 560 480 6 George 180 100 2 2 560 720 7 Quality 100 70 3 1 370 400 (a) What formula is in F2 to calculate the employee’s costs at the Grand Hotel? [2] (b) The maximum allowance is four times the Sunday to Thursday tariff. What formula is in G2? [1] (c) A manager wants to know whether an employee exceeded their maximum allowance at each hotel. Describe how the spreadsheet could be used to do this. [2] (d) A macro was written to convert the tariff rate into different currencies. The exchange rate was taken directly from a website. What is the advantage of using a macro to do this? [1]

10 © UCLES 2012 0420/13/M/J/12 For Examiner's Use 9 Vehicles passing over a bridge are detected automatically using sensors and a computer. (a) What sensors could be used? [1] (b) The graph below shows the number of vehicles counted during certain periods of the day. This graph is produced automatically at the end of each day. 80 70 60 50 40 30 20 10 0 Number of vehicles Bridge traffic on 1 March 2012 Time period 12-6 6-9 9-12 12-4 4-12 A record is created each time a vehicle is detected. These records are processed to generate the graph and for other purposes. What data need to be stored in each record? [2] (c) State two other methods of automatic data capture. In each case, name an application which would use this method. Method 1 Application 1 Method 2 Application 2 [4]

11 © UCLES 2012 0420/13/M/J/12 [Turn over For Examiner's Use 10 Jatinder uses Internet banking. (a) Give one benefit and one drawback of using Internet banking. Benefit Drawback [2] She uses a 5-digit PIN. (b) Every time she logs on, she is asked to give 3 random digits from the PIN. She was asked to give her 3rd, 1st and 4th digit. This changes every time she logs on. Give a reason for this. [1] (c) A different application needs the whole PIN to be input. The following code has been written to check the PIN: c = 0 INPUT PIN x = PIN REPEAT x = x/10 c = c + 1 UNTIL x < 1 IF c < 5 THEN PRINT “error in PIN entered” ELSE PRINT “PIN OK” ENDIF (i) What value of c and what message would be output if the following PINs were entered? 5 1 0 2 0 Value of c: Message: 5 1 2 0 Value of c: Message: [2] (ii) What type of validation check is being carried out here? [1]

12 © UCLES 2012 0420/13/M/J/12 For Examiner's Use 11 A simulation using a mathematical model is being used to forecast the weather one week in advance. (a) (i) State what data are gathered for this model. (ii) Explain how the data are gathered for this model. [2] (b) (i) Describe how the simulation can predict the weather for the next seven days. (ii) Describe in what format the predicted weather can be shown. [2]

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14 © UCLES 2012 0420/13/M/J/12 For Examiner's Use 12 (a) (i) Complete the truth table for the following logic circuit, which is made up of NAND gates: A B X A B 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]

15 © UCLES 2012 0420/13/M/J/12 [Turn over For Examiner's Use (b) Complete the truth table for the following logic circuit: A B X C AND NOT OR OR A B C 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]

16 © UCLES 2012 0420/13/M/J/12 For Examiner's Use 13 Andrew is sending a large document to a printer. (a) State the name for the area of memory used to store temporarily the data being sent to the printer. [1] (b) The printer runs out of paper during the printing job. A signal is sent back to the computer to temporarily stop its current task. Name this type of signal. [1] (c) When trying to save this document after it was printed, the computer stops responding. Give two reasons why the computer might stop responding. 1 2 [2] (d) Andrew ended up losing his electronic document. How could that have been prevented? [1]

17 © UCLES 2012 0420/13/M/J/12 [Turn over For Examiner's Use 14 A database was set up to show the properties of certain chemical elements. Part of the database is shown below. Name of element Element Symbol Atomic Number Atomic Weight Melting Point (C) Boiling Point (C) State at room temp oxygen O 8 16 - 218 - 183 gas iron Fe 26 56 1538 2861 solid mercury Hg 80 201 - 38 356 liquid bromine Br 35 80 - 7 59 liquid osmium Os 76 190 3033 5012 solid caesium Cs 55 133 28 671 solid gallium Ga 31 70 30 2204 solid argon Ar 18 40 - 189 - 186 gas silver Ag 47 108 961 2162 solid (a) How many fields are in each record? [1] (b) The following search condition was entered: (Melting Point (C) < 40) AND (Atomic Weight > 100) Using Element Symbol only, which records would be output? [2] (c) We need to know which elements have an atomic number greater than 50 and are solid at room temperature. Write down the search condition to find out these elements. [2] (d) The data are to be sorted in descending order of Boiling Point (C). Write down the new order of records using the Element Symbol only. [2]

18 © UCLES 2012 0420/13/M/J/12 For Examiner's Use 15 A vending machine has the choices shown below. 10 tea 11 with milk 12 with sugar 13 with milk and sugar 20 coffee 21 with milk 22 with sugar 23 with milk and sugar 30 hot chocolate 31 extra milk 32 extra sugar 33 with extra milk and extra sugar 40 cold water 41 hot water 42 fizzy water 50 coke 51 orange 52 lemon 60 chicken soup 61 tomato soup A customer uses a keypad to make their choice. Each number entered is represented in a 6-bit binary register. For example, key press 33 (hot chocolate with extra milk and extra sugar) is represented by: 1 32 0 16 0 8 0 4 0 2 1 1 (a) (i) If a customer chooses coffee with milk and sugar what is the key press? (ii) How is it represented in the 6-bit register? 32 16 8 4 2 1 [2] (b) If the 6-bit register shows 1 0 1 0 0 1 what drink has the customer chosen? [1]

19 © UCLES 2012 0420/13/M/J/12 [Turn over For Examiner's Use (c) A customer using the vending machine gets an error message after keying in their selection. What could have caused this error message? [1] (d) It was decided to split the register so that each digit was represented by its own 3-bit register: For example, 4 2 would now be represented as: 4 2 1 4 2 1 1 0 0 0 1 0 (i) What drink has been chosen if the 3-bit registers contain: 4 2 1 4 2 1 1 1 0 0 0 0 [1] (ii) How would the lemon option be shown on both types of register? 32 16 8 4 2 1 4 2 1 4 2 1 [2] (iii) What is the advantage of using two 3-bit registers rather than one 6-bit register? [1]

20 © UCLES 2012 0420/13/M/J/12 For Examiner's Use 16 A car park uses sensors and a microprocessor to monitor cars leaving and entering. The car park is open 24 hours every day. The parking fee is $10 per day. The following flowchart shows how the IN and OUT barriers are controlled. Some of the statements are missing. Using item numbers only, insert the correct item numbers into the flowchart from the item list. START any signal received from IN sensor? Yes Yes Yes No read the IN sensor read the OUT sensor No No Yes No

21 © UCLES 2012 0420/13/M/J/12 [Turn over For Examiner's Use List of statements Item Number Description 1 activate motor to raise IN barrier 2 activate motor to raise OUT barrier 3 any signal received from OUT sensor? 4 decrease number of cars in car park by 1 5 increase number of cars in car park by 1 6 is car park full? 7 is the car park fee paid? 8 OUTPUT “car park full” 9 OUTPUT “please pay car park fee at pay machine” 10 use ADC to convert IN sensor signal to digital 11 use ADC to convert OUT sensor signal to digital 12 use DAC to convert computer signal to analogue signal to operate IN barrier 13 use DAC to convert computer signal to analogue signal to operate OUT barrier 14 wait 30 seconds and then close barrier [6]

22 © UCLES 2012 0420/13/M/J/12 For Examiner's Use 17 Write an algorithm, using pseudocode or a program flowchart only, which: • inputs the population and land area for 500 countries, • calculates the population density (i.e. population/land area) for every country, • outputs the largest and smallest population density, • outputs the average population for all 500 countries. [6]

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24 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 2012 0420/13/M/J/12 BLANK PAGE

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS International General Certificate of Secondary Education MARK SCHEME for the May/June 2012 question paper for the guidance of teachers 0420 COMPUTER STUDIES 0420/13 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 must be read in conjunction with the question papers and the report on the examination. • Cambridge will not enter into discussions or correspondence in connection with these mark schemes. Cambridge is publishing the mark schemes for the May/June 2012 question papers for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses. www.XtremePapers.com

Page 2 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – May/June 2012 0420 13 © University of Cambridge International Examinations 2012 1 1 mark per correct row. keyboard microphone speaker webcam VoIP

video conferencing


instant messaging
Correct Answer Only [3] 2 viruses e.g. – use anti-virus software // regular virus scans – don’t open/use disks // don’t open email attachments from unknown sources Hacking e.g. – passwords / user IDs – firewalls Spyware e.g. – anti-spyware software – delete cookies at end of session Phishing e.g. – don’t open emails from unknown sources – don’t divulge personal information via email / unsecure website – ensure that the site viewed has a valid security certificate (SSL) tapping into wireless networks e.g. – secured wifi network (protected by passwords) – encryption / WEP – no broadcast of network ID [5] 3 (a) Any three from: – questionnaires – interviews – observation – looking at existing paperwork [3] (b) 0 marks for name, 2 marks for reasons which MUST tie up with name Questionnaires / interviews – possible to obtain information direct from customers – possible to obtain information direct from staff – customers/staff can take questionnaires away to answer in own time – interviews allow first hand information to be gathered/questions -asked can be tailored to the individual

Page 3 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – May/June 2012 0420 13 © University of Cambridge International Examinations 2012 Observation / existing paperwork – sees first hand airport operations – doesn’t rely on opinions of customers/staff – helps determine what hardware is needed – helps to determine memory size/storage devices [2] 4 (a) Any three from: – sound – animations – video – links to Internet websites – slide transitions – use of colours [3] (b) Any two from: – less expensive because e.g. no paper/ink required – can be interactive (chance to ask questions) – can explain things better because e.g. addition of animation/video – newsletters tend to be thrown away without reading/need distributing [2] 5 pendown forward 20 left 90 - - - - - - - - - - - - forward 10 right 90 (1 mark) forward 20 - - - - - - - - - - - - right 90 forward 40 right 90 (1 mark) forward 20 right 90 - - - - - - - - - - - - forward 10 right 45 (1 mark) forward 14 - - - - - - - - - - - - repeat 3 or left 90 left 90 or forward 14 forward 14 or left 90 endrepeat or forward 14 (1 mark) left 90 forward 14 - - - - - - - - - - - - right 135 forward 20 (1 mark) (PENUP) [5]

Page 4 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – May/June 2012 0420 13 © University of Cambridge International Examinations 2012 6 (a) C L N S T A B 1 0 0 0 0 8 4 2 1 4 4 3 1 3 2 2 6 5 8 4 3 1 9 4 2 5 3 2 11 1 3 6 2 2 13 2 2 7 0 13 1 2 8 1 3 14 5 5 9 0 14 4 0 10 4 4 18 5 4 11 5 1 19 1 mark 1 mark 1 mark 1 mark 1 mark < - - - - 1 mark - - - - > [6] (b) L = 5 } } 1 mark S = 3 } T = 19 } 1 mark [2]

Page 5 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – May/June 2012 0420 13 © University of Cambridge International Examinations 2012 7 (a) virtual tour Any two from: – hot spots to move from room to room – ability to zoom in and out of rooms – ability to rotate around the room (panning) – voiceovers interactive map Any two from: – how to get to hotel from some starting point on the map – use of satellite photos and map superimposed – zoom in/zoom out – move north, south, east and west – use of “pin head” to show location of hotel – hotspots with information on that area – how to get from one part of the hotel to another room booking online Any two from: – calendar function// room availability for given dates – type of room – number of guests – price per room – hotel facilities e.g. breakfast/full board/half board – special requirements – special offers – payment [6] (b) Any one from: – safe credit card payment facility – hyperlinks to other web pages/websites – local weather forecast [1] 8 (a) = (D2 * B2) + (E2 * C2) 1 mark 1 mark [2] (b) = B2 * 4 [1]

Page 6 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – May/June 2012 0420 13 © University of Cambridge International Examinations 2012 (c) Any two from: – use (=) IF(F2 > G2, “exceeded”, “within range”) – replicate formula down to row 7 OR – F2-G2 – if result is positive … OR – draw graph of data in columns F and G – compare values on graph to determine if exceeded OR – drawing line of unit gradient (on a scatter graph of total cost versus maximum allowance) – compare values on graph to determine if exceeded [2] (d) Any one from: – automatic calculation – no need to create formula (etc.) every time on the spreadsheet – can be assigned to a keyboard shortcut and launched [1] 9 (a) Any one from: – infra red sensor – pressure sensor/induction loop – radar [1] (b) – time of day – date [2] (c) 1 mark for name + 1 mark for correct application – barcode e.g. – stock taking in supermarket – getting prices at POS – library system – tracking systems (e.g. parcels) – RFID e.g. – identifying/tracking individual items (livestock, vehicles, people) – biometrics e.g. – finger printing, face images, etc. as security systems – magnetic stripe e.g. – security cards (e.g. hotel room keys) – credit/debit cards/ATMs/banking – loyalty cards – OCR/OMR e.g. – scanning in documents/photos/exam papers – microphones e.g. – interface (input) to a computer (used by disabled people) [4]

Page 7 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – May/June 2012 0420 13 © University of Cambridge International Examinations 2012 10 (a) Any one benefit and one drawback from: benefit: – can bank at any time 24/7 – save money on travelling – save time not travelling to bank – can bank from anywhere – can do transactions/look after account drawbacks: – need computer equipment/internet – fear of hacking , viruses, etc. – lack of one to one with bank – creation of “ghost towns” – reduced socialising – cause of redundancies – possibility of mismanaging account – lack of counter services (drawing out cash) [2] (b) Any one from: – stops hackers getting all of the PIN characters [1] (c) (i) 51020: value of c: 5 message: PIN OK (1 mark) 5120: value of c: 4 message: ERROR (1 mark) [2] (ii) length check [1] 11 (a) (i) what data is gathered: Any one from: – pressure – temperature – humidity – wind speed/direction – historic data [1] (ii) how data is gathered: Any one from: – sensors – satellites – airline pilots send in information – meteorological/weather balloons/station [1] (b) (i) Any one from: – information from sensors/satellites sent to computer – data compared to stored information – which contains known weather patterns – predictions made based on these comparisons – expert system [1]

Page 8 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – May/June 2012 0420 13 © University of Cambridge International Examinations 2012 (ii) Any one from: – produces weather maps showing isobars, etc. – computer can show weather changes graphically/by animations [1] 12 (a) (i) A B X 0 0 0 0 1 1 1 0 1 1 1 1 [2] (ii) OR gate [1] (b) A B C X 0 0 0 1 0 0 1 0 0 1 0 1 0 1 1 1 1 0 0 1 1 0 1 0 1 1 0 1 1 1 1 1 [4] 13 (a) Any one from: – buffer – RAM [1] (b) – interrupt [1] } 1 mark } 1 mark } 1 mark } 1 mark } 1 mark } 1 mark

Page 9 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – May/June 2012 0420 13 © University of Cambridge International Examinations 2012 (c) Any two from: – hardware problem (e.g. head crash on disk drive) – software “glitch” – viruses – disconnected printer cable – automatic update in progress – too many applications open [2] (d) Any one from: – backup the document – enable automatic saving of work – manually save document every 10 minutes – save before printing [1] 14 (a) 7 [1] (b) Hg, Cs (1) (1) Correct Answer Only [2] (c) (Atomic Number > 50) AND (State at room temp = “solid”) < - - - - - 1 mark - - - - -> < - - - - - - - - - - - 1 mark - - - - - - - - - - -> Or (State at room temp = “solid”) AND (Atomic Number > 50) < - - - - - - -1 mark - - - - - - - > < - - - - - - - - -1 mark - - - - - - - - > Must use exact spelling [2] (d) Os, Fe, Ga, Ag, Cs, Hg, Br, O, Ar [2] 15 (a) key press: 2 3 represented by: 0 1 0 1 1 1 [2]

Page 10 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – May/June 2012 0420 13 © University of Cambridge International Examinations 2012 (b) drink chosen: hot water/41 [1] (c) Any one from: – incorrect number typed/keyed in – not one of the accepted codes used – code not recognised – machine malfunction (e.g. no cups) [1] (d) (i) – chicken soup/60 [1] (ii) 5 2 1 0 1 0 1 0 1 1 0 1 0 0 [2] (iii) – gives an additional row of options – now have 0 to 77 instead of only 0 to 63 [1]

Page 11 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – May/June 2012 0420 13 © University of Cambridge International Examinations 2012 16 [6] *Instead of 5, 12, 1 can have: “instead of 4, , 13, 2 can have: 12, 1, 5 13, , 2, 4 12, 5, 1 13, , 4, 2 START read the IN sensor any signal received from IN sensor? read the OUT sensor 10 3 6 8 11 4” 7 9 13” 2” 5* 12* 1* 14 No Yes No Yes Yes No No Yes 1 mark 1 mark 1 mark 1 mark 1 mark 1 mark

Page 12 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – May/June 2012 0420 13 © University of Cambridge International Examinations 2012 17 marking points • Initialisation (smallest, largest, total) (could be first input) • correct loop (also: repeat … until n = 500, while n <> 500 do …) • input (inside a loop) • calculate the density • check on largest density + action taken • check on smallest density + action taken • find population total + calculate average population • print values (outside loop + some evidence of processing taking place) e.g. smallest = 10000: largest = 0: total = 0 (1 mark) for country = 1 to 500 (1 mark) input population, area (1 mark) density = population/area (1 mark) if density > largest then largest = density (1 mark) if density < smallest then smallest = density (1 mark) total = total + population next country (1 mark) average = total/500 print largest, smallest, average (1 mark) [6]