Cambridge IGCSE Computer Studies 0420 — 2011 May/June Paper 1 · Variant 1

This document consists of 24 printed pages. IB11 06_0420_11/3RP © UCLES 2011 [Turn over *7786150739* For Examiner's Use UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS International General Certificate of Secondary Education COMPUTER STUDIES 0420/11 Paper 1 May/June 2011 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 2011 0420/11/M/J/11 For Examiner's Use 1 Give three tasks carried out by an operating system. 1 2 3 [3] 2 A user decides to use an Internet search engine to help locate a hotel. (a) What is a search engine? [1] (b) Give two possible problems the user might encounter when using a search engine. 1 2 [2]

3 © UCLES 2011 0420/11/M/J/11 [Turn over For Examiner's Use (c) The search engine found the website of a suitable hotel. Give three features you would expect to see on a hotel website. 1 2 3 [3]

4 © UCLES 2011 0420/11/M/J/11 For Examiner's Use 3 A worker at a company has to go through a logon procedure to gain access to her computer system. (a) The first thing she has to do is type in a user name and a password. Why is this done? [1] (b) The password is typed in twice. Why is this done? [1] A menu then appears on her screen. She chooses to connect to the Internet. (c) Describe two ways her computer system is protected against loss or corruption of files once the computer system is connected to the Internet. 1 2 [2]

5 © UCLES 2011 0420/11/M/J/11 [Turn over For Examiner's Use (d) The worker leaves her computer system for a 10-minute break. (i) From a health and safety aspect, why does she need to take a regular break? (ii) Apart from switching off her machine, how could she ensure her computer system was secure whilst taking her regular break? [2]

6 © UCLES 2011 0420/11/M/J/11 For Examiner's Use 4 The following diagram shows a typical expert system. Explanation System Working store Z X W Knowledge Base Editor Y (a) Name the missing labels W to Z using the following list of possible options. Inference Engine Expert System Shell Knowledge Base User Interface W X Y Z [4] (b) Name one of the components that makes up the knowledge base. [1] (c) Give one advantage and one disadvantage of using expert systems. Advantage: Disadvantage: [2]

7 © UCLES 2011 0420/11/M/J/11 [Turn over For Examiner's Use (d) Name two examples of the use of expert systems. 1 2 [2]

8 © UCLES 2011 0420/11/M/J/11 For Examiner's Use 5 Study the following flowchart very carefully: START STOP count = 1 total = 0 X = 0 count = count + 1 Is number > 0 ? total = total + number X = X + 1 average = total/X Is count <= 10 ? No No INPUT number OUTPUT average Yes Yes

9 © UCLES 2011 0420/11/M/J/11 [Turn over For Examiner's Use (a) Complete the trace table for the following data set: 15, -2, 0, 8, 0, 21, -8, -12, 1, 25 count number total X average OUTPUT [4] (b) What is the purpose of this flowchart? [1]

10 © UCLES 2011 0420/11/M/J/11 For Examiner's Use 6 Describe the role of computer software and hardware when producing animation effects in the television and film industry. [3] 7 A spreadsheet has been set up to compare the costs of types of fruit juice sold by a shop. A B C D 1 NAME OF FRUIT JUICE NORMAL PRICE PER BOTTLE ($) VOLUME OF BOTTLE (LITRES) COST PER LITRE ($) 2 Apple 3.50 1.0 3.50 3 Orange 2.80 1.0 2.80 4 Pomegranate 4.55 0.7 6.50 5 Caju 2.00 2.0 1.00 6 Mango 1.05 0.7 1.50 7 Average cost: 3.06 (a) (i) What formula is in cell D5 to calculate the cost of Caju juice per litre? (ii) What formula is in cell D7 to calculate the mean (average) cost of fruit juice per litre? [2] (b) What validation check could be carried out on the data in cells B2 to B6? [1]

11 © UCLES 2011 0420/11/M/J/11 [Turn over For Examiner's Use (c) Three extra columns are to be added to this spreadsheet: Column E will show a percent discount on the normal price of a bottle of fruit juice (as shown in column B); Column F will show this discount in dollars ($); Column G will show the price of a bottle of fruit juice after discount. Complete the spreadsheet by showing the formulas that need to be placed in cells F2 to F6 and G2 to G6. E F G 1 Percentage discount (%) Discount amount ($) Discounted price per bottle ($) 2 10 3 20 4 15 5 10 6 5 [4]

12 © UCLES 2011 0420/11/M/J/11 For Examiner's Use 8 Many computer-controlled systems use sensors to gather physical data. For example, temperature sensors are used in the control of central heating systems. (a) Name three other sensors and give a different application for each named sensor. Sensor 1: Application: Sensor 2: Application: Sensor 3: Application: [6]

13 © UCLES 2011 0420/11/M/J/11 [Turn over For Examiner's Use (b) Describe how temperature sensors are used in computer-controlled central heating systems. [3]

14 © UCLES 2011 0420/11/M/J/11 For Examiner's Use 9 An international company uses video-conferencing. The system is set up as follows: ( represents a person at the meeting) micro- phone micro- phone screen + web cam speakers conference room 1 conference room 2 (a) Describe how the video-conferencing system works. [4]

15 © UCLES 2011 0420/11/M/J/11 [Turn over For Examiner's Use (b) Give two reasons why video-conferencing is gaining in popularity. 1 2 [2]

16 © UCLES 2011 0420/11/M/J/11 For Examiner's Use 10 (a) Two logic gates are the AND gate and the OR gate. Complete the truth tables for these two gates: AND gate OR gate A B X A B X 0 0 0 0 0 1 0 1 1 0 1 0 1 1 1 1 [2] (b) Complete the truth table for the following logic circuit: A B C AND AND NOT OR X 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]

17 © UCLES 2011 0420/11/M/J/11 [Turn over For Examiner's Use 11 (a) Describe three features you would expect to find in a Computer Aided Design (CAD) package. 1 2 3 [3] (b) Give three different applications where CAD might be used. 1 2 3 [3]

18 © UCLES 2011 0420/11/M/J/11 For Examiner's Use 12 Many vehicles use Global Positioning Systems (GPS) to know their exact location at all times. (a) How does GPS work? [3] A taxi company uses GPS in all its vehicles. (b) One of its taxis is on Main Street and needs to go to Railway Street. How is GPS technology used to help the taxi driver get to his new destination? [2] (c) Name one other feature of GPS that could be useful to the driver. [1]

19 © UCLES 2011 0420/11/M/J/11 [Turn over For Examiner's Use (d) Give two reasons why the GPS could take the driver to the wrong destination or cause error messages. 1 2 [2] 13 It has been decided to model the traffic flow at a busy road junction. (a) Describe how data is gathered for this model. [3] (b) Give two reasons why a model is used. 1 2 [2]

20 © UCLES 2011 0420/11/M/J/11 For Examiner's Use 14 (a) Name and draw two common types of network topology. Type 1: Type 2: [2] (b) Give two advantages of networking computers. 1 2 [2]

21 © UCLES 2011 0420/11/M/J/11 [Turn over For Examiner's Use 15 A database showing the population of world cities has been produced. A section of the database is shown below. Ref No Name of City Country Area City Population (m) Urban Population (m) Capital 1 Tokyo Japan Asia 33.2 34.1 Yes 2 New York USA America 17.8 21.9 No 3 Sao Paulo Brazil America 17.7 20.2 No 4 Seoul S Korea Asia 17.5 22.3 Yes 5 Mexico City Mexico America 17.4 22.7 Yes 6 Osaka Japan Asia 16.4 16.8 No 7 Manila Philippines Asia 14.8 14.9 Yes 8 Mumbai India Asia 14.4 19.7 No 9 Jakarta Indonesia Asia 14.3 17.2 Yes 10 Calcutta India Asia 12.7 15.6 No (a) How many records are shown above? [1] (b) Using Ref No only, which records would be found if the following search condition was typed in (Country = “India” OR Area = “America”) AND (Capital = “No”) [2] (c) Write a search condition to find the cities in Asia with a city population greater than 17 million OR an urban population greater than 20 million. [2] (d) Give one advantage of using Y or N rather than Yes or No in the Capital column. [1]

22 © UCLES 2011 0420/11/M/J/11 For Examiner's Use 16 A floor turtle can use the following instructions: Instruction Meaning FORWARD d Move d cm forward BACKWARD d Move d cm backward LEFT t Turn left t degrees RIGHT t Turn right t degrees REPEAT n Repeat the next set of instructions n times ENDREPEAT End of REPEAT loop PENUP Raise the pen PENDOWN Lower the pen (Each square in the drawing below is 10 cm by 10 cm.) Start Finish

23 © UCLES 2011 0420/11/M/J/11 [Turn over For Examiner's Use Complete the set of instructions to draw the above shape (shown in bold lines). PENDOWN LEFT 90 REPEAT [5]

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 2011 0420/11/M/J/11 For Examiner's Use 17 Daniel lives in Italy and travels to Mexico, India and New Zealand. The times differences are: Country Hours Minutes Mexico -7 0 India +4 +30 New Zealand +11 0 Thus, if it is 10:15 in Italy it will be 14:45 in India. (a) Write an algorithm, using pseudocode or otherwise, which: • Inputs the name of the country • Inputs the time in Italy in hours (H) and minutes (M) • Calculates the time in the country input using the data from the table • Outputs the country and the time in hours and minutes [4] (b) Describe, with examples, two sets of test data you would use to test your algorithm. 1 2 [2]

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS International General Certificate of Secondary Education MARK SCHEME for the May/June 2011 question paper for the guidance of teachers 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 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 2011 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 2011 0420 11 © University of Cambridge International Examinations 2011 1 Any three from: – handling interrupts – input/output/peripheral/device control – spooling – multitasking/JCL/batch processing – multiprogramming – user interface – load/run software – processor management/task management – file (copy/save/delete etc) management – memory management – user accounts – utility tasks (defrag, format etc.) – error reporting/handling – security management – power management [3] 2 (a) Any one point from: – program searches documents for key words/query and returns a list – software that searches for sites based on words input – use their own database to locate data defined by key words/query input [1] (b) Any two points from: – too wide a search/too much information/irrelevant information found – “unwanted”/undesirable sites found during the search – picks up words with same spelling but different meaning – search engine loyalty/funded by advertising puts websites top of list – may produce out of date sites – misleading/incorrect information [2] (c) Any three features from: – shopping basket – checkout – secure credit card payment – hyperlinks to other sites – drop down boxes/calendar with available dates – virtual tour of the hotel/hotel facilities – currency conversions – interactive map/directions to hotel/contact details – drop down boxes with room rates – confirmation by email/textmessage – form to fill in customer details/booking form – special offers [3]

Page 3 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – May/June 2011 0420 11 © University of Cambridge International Examinations 2011 3 (a) Any one from: – prevents unauthorised access to files/the computer system – access to her own directories – allow authorised access [1] (b) Any one from: – verification check – (double check) password is correct [1] (c) Any two from: – firewall – anti-virus software – (automatic) backup of data – auto-save [2] (d) (i) Any one from: – repetitive strain injury (RSI) / pain in wrist/fingers – carpal tunnel syndrome – headaches/eyestrain/back ache/neck ache [1] (ii) Any one from: – “lock” computer system – automatic screen saver (after short time of inactivity) – log off from the system – if computer in an office, lock the office door [1] 4 (a) W = User Interface X = Inference Engine Y = Expert System Shell Z = Knowledge Base [4] (b) Any one from: – Facts – Rules Base [1] (c) Any one advantage from: – reduces the time taken to solve a problem – can predict future faults – can lower wage bills (less skilled work force needed) – can be used in countries where the necessary skills are rare – can have access 24/7 – less likely to miss a question Any one disadvantage from: – expensive system to set up/purchase – necessary to do training on the new system – must be kept up-to-date [2]

Page 4 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – May/June 2011 0420 11 © University of Cambridge International Examinations 2011 (d) Any two examples from: e.g. – medical diagnosis – diagnostics with example (car engine faults, electronic components) – tax/financial calculations – chess – mineral/oil prospecting – animal/plant classification [2] 5 (a) count number total x average OUTPUT 1 0 0 2 15 15 1 3 –2 4 0 5 8 23 2 6 0 7 21 44 3 8 –8 9 –12 10 1 45 4 11 25 70 5 14 14 <- - - - - - 1 mark - - - - - - - ->< - 1 mark ->< - 1 mark ->< - - - - - - - - 1 mark - - - - - - - - -> [4] (b) Find the average of all positive numbers entered [1] 6 Any three points from: – computer s/ware helps produce more realism – ability to “move” mouth properly to accurately mimic speech – can store frames straight to dvd (or similar) – speeds up/simplifies editing process – removes need for several artists to draw the animations – use of tweening speeds up the process – reference to morphing – reference to avatars – reference to avars (animation variables) – reference to rendering [3] 7 (a) (i) = B5/C5 [1] (ii) = (D2 + D3 + D4 + D5 + D6)/5 OR = AVERAGE(D2:D6) OR = SUM(D2:D6)/5 [1] (b) Any one from: – character/type check – range check – format check [1] } 1 } 1 } 1 } 1

Page 5 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – May/June 2011 0420 11 © University of Cambridge International Examinations 2011 (c) E F G 1 Percent discount (%) Discount amount ($) Discounted price per bottle ($) 2 10 = B2 * E2/100 = B2 – F2 3 20 = B3 * E3/100 = B3 – F3 4 15 = B4 * E4/100 = B4 – F4 5 10 = B5 * E5/100 = B5 – F5 6 5 = B6 * E6/100 = B6 – F6 NOTE: 1 mark for first formula in F2 1 mark for replication of formula in F3 through to F6 1 mark for first formula in G2 1 mark for replication of formula in G3 through to G6 [4]

Page 6 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – May/June 2011 0420 11 © University of Cambridge International Examinations 2011 8 (a) 1 mark for naming the sensor + 1 mark for correct application of named sensor (applications MUST be different) Named sensor Application of named sensor Humidity Moisture (water) greenhouse environmental control spin drier in automatic washing machine libraries/archives where moisture levels need controlling oxygen fish tank/aquarium environmental monitoring car engine management system/fuel injection system light burglar alarm automatic doors greenhouse environmental control infra red automatic doors car in correct place to allow paint spraying in car factory burglar alarm pressure traffic control automatic doors burglar alarm gas Environmental monitoring Safety system [6]

Page 7 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – May/June 2011 0420 11 © University of Cambridge International Examinations 2011 (b) Any three points from: – sensor relays reading back to computer – if reading is analogue, need an analogue to digital converter (ADC) – computer compares reading with stored value – sends signal to actuators – signal converted using digital to analogue converter (DAC) – actuator alters factors such as heating, coolers, etc. – cycle continues / output affects input accept a diagram such as: [3] How to mark a diagram: 1 mark for link between sensor(s) and computer 1 mark for showing an ADC 1 mark for showing a DAC 1 mark for link from computer to actuator 1 mark for arrow implying cycling of system 9 (a) Any four points from: – each “conference room” needs to log into system – delegates speak into microphone – webcam takes video image – uses Internet/WAN/broadband/modem to transmit data – use of compression software for video/audio – use of CODEC (which converts and compresses analogue data into digital data and sends over digital links) – echo cancellation software (allows talking in real time/keeps everything in sync) – video images seen (on screen)/audio heard (using speakers) in real time [4] (b) Any two points from: – faster communications now available (e.g. high speed broadband) – safety reasons (e.g. risk of terrorism attacks on flights) – costs (saves on overseas travelling/hotel costs) – cheaper equipment costs [2] ADC computer DAC actuator Central heating devices sensors

Page 8 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – May/June 2011 0420 11 © University of Cambridge International Examinations 2011 10 (a) AND gate OR gate (1 mark for correct X column in each gate) [2] (b) A B C X 0 0 0 0 0 0 1 0 0 1 0 1 0 1 1 0 1 0 0 0 1 0 1 0 1 1 0 1 1 1 1 1 [4] 11 (a) Any three features from: e.g. – rotate, enlarge, change colour etc. – costings – library of parts – validation of design against specification – ability to do 2D/3D designs – link into CAM – create engineering drawings from solid models – calculate/test mass, stress etc. in new designs – electronic component packing [3] (b) Any three from: e.g. – architecture (houses, office blocks, etc.) – engineering (bridges, roads, etc.) – interior design (kitchens, bathrooms, etc.) – water supply/sewer systems – aerospace – car (vehicle) design – chemical/nuclear plant design – factory layouts – consumer goods design (e.g. mobile phones) – ship building – fashion design – design of electronic components [3] A B X A B X 0 0 0 0 0 0 0 1 0 0 1 1 1 0 0 1 0 1 1 1 1 1 1 1 } } } } 1 1 1 1

Page 9 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – May/June 2011 0420 11 © University of Cambridge International Examinations 2011 12 (a) Any three points from: – satellites transmit signals to sat nav computer – computer receives/interprets these signals – system depends on very accurate timing/use of atomic clocks – each satellite transmits data including location and time – computer in taxi calculates its position based on at least 3 satellites – at least 24 satellites in operation at a given time – position of vehicle is within 1 metre – refer to triangulation: [3] (b) Any two points from: – maps stored in sat nav memory – shows directions on a screen – voice output gives driver directions/instructions – plots route in advance – GPS knows exactly where vehicle is – recalculates route if driver makes a mistake [2] (c) Any one point from: – can estimate time of arrival – can warn of speed cameras (etc.) – can warn of road works/diversions/traffic congestion – can warn if exceeding speed limit – can give fastest/most scenic route etc. – can give location of petrol station/hotel etc [1] (d) Any two reasons from: – wrong/outdated maps stored on system – inaccurate timing – (temporary) loss of signal – incorrect start point/end point selected/keyed in – road works/accident have closed the “expected” route [2] satellite 1 satellite 2 Exact location of vehicle satellite 3

Page 10 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – May/June 2011 0420 11 © University of Cambridge International Examinations 2011 13 (a) Any three points from: – collect data at different times of the day – data collected by filling in paper records – can use hand held devices to collect data – use of sensors to collect data – time how long it takes for vehicle to cross junction – count number of vehicles in all directions [3] (b) Any two points from: – much safer (if errors made in real life, could be fatal) – less costly (can try out things first on the model) NEED REASON – able to test out various scenarios first – can optimise timings of lights etc. at junctions – model can be applied to other junctions – much quicker than doing the real thing [2] 14 (a) 1 mark for name + correct drawing of each type of network ring star bus [2] (b) Any two advantages from: – sharing of resources (hardware and software) – easier to communicate computer to computer – central database – thus all users share same information – easier to control what users can do (e.g. block Internet access) – can work from any station and access data [2] 15 (a) 10 [1] (b) 2, 3, 8, 10 1 mark per two correct records Loose 1 mark for each additional record [2] (c) (Area = “Asia”) AND (City Population(m) > 17 OR Urban Population(m) > 20) <- - - - 1 mark - - - -> < - - - - - - - - - - - - - - - - 1 mark - - - - - - - - - - - - -- - - - - -> OR (Area = “Asia” AND City Population(m) > 17) OR (Area = “Asia” AND Urban Population(m) > 20) < - - - - - - - - - - - - - - -1 mark - - - - - - - - - -- - - - -> < - - - - -- - - - - - - - - - 1 mark - - - -- - - - - - - - - -> [2]

Page 11 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – May/June 2011 0420 11 © University of Cambridge International Examinations 2011 (d) Any one advantage from: – less likely for entry/typing errors – uses less memory to store records – faster data entry [1] 16 PENDOWN LEFT 90 REPEAT 3 FORWARD 30 1 mark RIGHT 90 ------------------------------------------------------------------------------------------- ENDREPEAT FORWARD 10 1 mark LEFT 90 OR PENUP ------------------------------------------------------------------------------------------- PENUP OR LEFT 90 FORWARD 10 1 mark PENDOWN ------------------------------------------------------------------------------------------- REPEAT 2 OR REPEAT 3 FORWARD 20 1 mark ------------------------------------------------------------------------------------------- RIGHT 90 ENDREPEAT FORWARD 20 OR (LEFT/RIGHT 180) 1 mark (LEFT 90) Give a mark for each correct group of statements [5] Alternative answer for last 2 marks: FORWARD 20 RIGHT 90 1 mark ------------------------------------------------------------------------------------------- FORWARD 20 RIGHT 90 1 mark FORWARD 20

Page 12 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – May/June 2011 0420 11 © University of Cambridge International Examinations 2011 17 (a) input name$ input H, M if name$ = “Mexico” then H = H – 7 else if name$ = “India” then H = H + 4: M = M + 30 else if name$ = “New Zealand” then H = H + 11 else print “error” print H, M Marking points – 1 mark for two inputs for country and hours/mins – 1 mark for check on Mexico – 1 mark for check on New Zealand – 1 mark for check on India – 1 mark for error check – 1 mark for output in correct place [4] (b) Any two sets of test data from: Normal hours: (hours which do not change the day) e.g. 8 hours which change the day (e.g.. 13 + country = New Zealand) Normal minutes (which do not change the hour) eg.25 minutes which change the hour (e.g. 40 + country=India) [2]