Cambridge IGCSE Computer Studies 0420 — 2011 Oct/Nov Paper 1 · Variant 1

This document consists of 19 printed pages and 1 blank page. IB11 11_0420_11/2RP © UCLES 2011 [Turn over *9106074384* For Examiner's Use UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS International General Certificate of Secondary Education COMPUTER STUDIES 0420/11 Paper 1 October/November 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/O/N/11 For Examiner's Use 1 Name three of the stages in the system life cycle. 1 2 3 [3] 2 (a) Give one benefit of storing music files in MP3 format. [1] (b) Describe the type of memory used in MP3 players. [2] 3 Give three features expected in a data protection act. 1 2 3 [3]

3 © UCLES 2011 0420/11/O/N/11 [Turn over For Examiner's Use 4 The following flowchart shows how barcodes are used at the point of sale in an automatic stock control system. Select statements from the list below, using numbers only, to complete the flowchart. START STOP READ barcode on item 1 any more barcodes to read? 2 find barcode in stock database 3 has item already been ordered? 4 has barcode been found in file? 5 has barcode scanned correctly? 6 is number in stock <= reorder level? 7 manually key in barcode 8 send out orders to suppliers 9 subtract 1 from item stock level List of statements No. No No No No No Yes Yes Yes Yes Yes [5]

4 © UCLES 2011 0420/11/O/N/11 For Examiner's Use 5 (a) State what is meant by Computer Aided Design (CAD). [1] (b) Give three different applications that make use of CAD. 1 2 3 [3] (c) Name three specialist input/output devices used in CAD. 1 2 3 [3]

5 © UCLES 2011 0420/11/O/N/11 [Turn over For Examiner's Use 6 (a) Name two pieces of hardware needed to enable video-conferencing to take place using a standard computer system. 1 2 [2] (b) State one piece of specialist software needed to carry out video-conferencing. [1] (c) A company has decided to use video-conferencing rather than instant messaging. (i) Give one advantage of doing this. (ii) Give one disadvantage of doing this. [2] (d) Give one reason why use of video-conferencing has increased over the last ten years. [1]

6 © UCLES 2011 0420/11/O/N/11 For Examiner's Use 7 Carefully study the following flowchart: START STOP INPUT number count = 1: total = 0: neg = 0 OUTPUT total, neg INPUT temp temp >= 20 ? temp <= 0 ? count <= number ? count = count + 1 total = total + temp neg = neg + 1 No No No Yes Yes Yes Complete the trace tables for the following two sets of test data: (i) number = 7, temp = -5, 0, 5, -4, 0, 10, -2 (ii) number = 6, temp = 21, 20, 30, 19, 21, 15

7 © UCLES 2011 0420/11/O/N/11 [Turn over For Examiner's Use (i) trace table: number count temp total neg OUTPUT (ii) trace table: number count temp total neg OUTPUT [6]

8 © UCLES 2011 0420/11/O/N/11 For Examiner's Use 8 You have been asked to write an article on how an expert system is developed. What would you include in your article? [3] 9 A spreadsheet has been designed to calculate the fuel economy for 6 cars: A B C D 1 car distance (km) fuel used (litres) economy (km/litre) 2 car 1 48 4.0 12.0 3 car 2 160 9.0 17.8 4 car 3 70 4.5 15.6 5 car 4 200 20.0 10.0 6 car 5 150 33.0 4.5 7 car 6 300 15.0 20.0 8 average economy: 13.3 9 best economy: 20.0 (a) (i) What formula is in cell D2 to calculate the economy for car 1? (ii) What formula is in cell D8 to calculate the average economy for all 6 cars? (iii) What formula is in cell D9 to calculate the best (highest) economy? [3] (b) If cell B7 was changed to 200, which cells would be automatically updated? [2]

9 © UCLES 2011 0420/11/O/N/11 [Turn over For Examiner's Use (c) Fuel economy is often given in the form litres per 100 km. A column E is to be added to the spreadsheet to contain these new economy values. What formula needs to be in E7 to find the economy of car 6 in litres per 100 km? [2] 10 A company’s technical services are now available on the Internet as well as using call centres. (a) Give two advantages to the customer of using call centres. 1 2 [2] (b) Give two advantages to the customer of using technical services on the Internet. 1 2 [2] (c) Describe two effects on company staff of replacing the call centres with Internet services. 1 2 [2]

10 © UCLES 2011 0420/11/O/N/11 For Examiner's Use 11 Computer memories are measured in terms of the number of bytes. (a) (i) What is meant by the term byte? (ii) What is meant by a Gigabyte? [2] (b) Flash memories and CD-RWs are used as backing media for computers. Give two differences between these two media. 1 2 [2] 12 The conditions in a fish tank are being controlled using sensors and a microprocessor. To keep the fish healthy, the temperature must be at 25°C and the oxygen content needs to be 20 ppm (parts per million). The tank contains a heater and an oxygen inlet controlled by a valve. microprocessor sensor A sensor B heater oxygen supply

11 © UCLES 2011 0420/11/O/N/11 [Turn over For Examiner's Use (a) Name the two sensors used in this application. Sensor A Sensor B [2] (b) Describe how the sensors and the microprocessor are used to maintain the correct conditions in the fish tank. [4] (c) What safeguards would be needed to stop the fish tank temperature rising too high? [1]

12 © UCLES 2011 0420/11/O/N/11 For Examiner's Use 13 Aeroplanes now use Global Positioning Systems (GPS) to determine their location. (a) Describe how the computer on board the aeroplane uses GPS to find its exact location. [4] (b) Give two benefits of using GPS in this application. 1 2 [2]

13 © UCLES 2011 0420/11/O/N/11 [Turn over BLANK PAGE

14 © UCLES 2011 0420/11/O/N/11 For Examiner's Use 14 An alarm, X, gives a signal (i.e. X = 1) when a car fuel injection system gives certain fault conditions. The inputs are: input binary value condition 0 pressure < 5 bar P 1 pressure >= 5 bar 0 revs > 8000 rpm R 1 revs <= 8000 rpm 0 temp > 120 °C T 1 temp <= 120 °C The alarm returns a value of 1 if: either (i) pressure < 5 bar AND revs > 8000 rpm or (ii) revs <= 8000 rpm AND temp > 120 °C (a) Draw the logic circuit for the above system using these logic gates. AND NOT OR [6]

15 © UCLES 2011 0420/11/O/N/11 [Turn over For Examiner's Use (b) Complete the truth table for this alarm system. P R T 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 2011 0420/11/O/N/11 For Examiner's Use 15 A company selling CDs uses a unique 6-digit identification number for each CD title. The right-most digit (position 1) is a check digit. For example, 6 3 5 0 4 6 3 1 2 4 1 9 check digit digit position identification number The validity of the number and check digit is calculated as follows: • multiply each digit by its digit position • add up the results of the multiplications • divide the answer by 11 • if the remainder is 0, the identification number and check digit are valid (a) Show whether the following identification numbers are valid or not. You must show how you arrived at your answer. (i) 4 2 1 9 2 3 working: valid or not valid? (ii) 8 2 0 1 5 6 working: valid or not valid? [3]

17 © UCLES 2011 0420/11/O/N/11 [Turn over For Examiner's Use (b) Find the check digit for the following identification number: 5 0 2 4 1 __ working: check digit: [2] (c) Describe, with examples, two different types of data entry errors that a check digit would detect. 1 2 [2]

18 © UCLES 2011 0420/11/O/N/11 For Examiner's Use 16 A company has bought some computers which can be used as stand-alone or networked. (a) When used as stand-alone, there is a risk of information being stolen. Give two ways this risk could be removed or minimised. 1 2 [2] (b) There are additional, different security risks when using the computers on a network. Describe two of these risks and how the system can be protected against them. Risk 1 Protection Risk 2 Protection [4] (c) The company use a star network which is linked externally to the Internet. (i) Draw a labelled diagram of a star network.

19 © UCLES 2011 0420/11/O/N/11 [Turn over For Examiner's Use (ii) Another type of network is a ring. Give one advantage of a star network when compared to a ring network. [2] (d) The company also decides to buy some laptop computers for use on the network. Give two desirable properties you would look for in the laptop processors. 1 2 [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 2011 0420/11/O/N/11 For Examiner's Use 17 (a) Write an algorithm, using pseudocode or flowchart only, which: • inputs three numbers • outputs the largest of the three numbers [3] (b) Write an algorithm, using pseudocode or flowchart only, which: • inputs 1000 numbers • outputs how many of these numbers were whole numbers (integers) (You may use INT(X) in your answer e.g. Y = INT(3.8) gives the value Y = 3) [4]

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS International General Certificate of Secondary Education MARK SCHEME for the October/November 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 October/November 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 – October/November 2011 0420 11 © University of Cambridge International Examinations 2011 1 Any three from: – fact finding – feasibility study – analysis – design – testing – documentation – implementation/changeover/installation – evaluation – maintenance [3] 2 (a) Any one from: – file size is small – fast to download/upload files – format can be played on several types of devices, e.g. mobile phone, CD player, laptop etc. [1] (b) Any two from: – type of EEPROM – non-volatile memories – solid state memories – NAND based memories – mini hard disk drives [2] 3 Any three from: – data must be up to date – data can only be read/used for the purpose for which it was collected – data must be accurate/relevant – data must be deleted/destroyed when no longer needed/don’t keep longer than necessary – data must be secure – data user must register what data is held – data must be used /collected fairly and lawfully – data must be protected from accidental damage – only authorised people can have access to the data – fines will be imposed for data mis-use – data should not be passed on to 3rd parties without owner’s permission – person can view data and have it changed if necessary [3]

Page 3 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – October/November 2011 0420 11 © University of Cambridge International Examinations 2011 4 START READ bar code on next item 2 6 3 8 9 Yes No No Yes 4 1 5 7 STOP No Yes No Yes No Yes [5] 1 mark 1 mark 1 mark 1 mark 1 mark

Page 4 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – October/November 2011 0420 11 © University of Cambridge International Examinations 2011 5 (a) Any one from: – software that can be used to design new products/amend existing products – makes use of features such as 2D, 3D, wire frames, library of parts, links to CAM [1] (b) Any three from: – aerospace – architecture – designing cars – designing consumer goods – chemical/nuclear plant design – designing electronic circuit boards – ergonomic design – landscape/garden design [3] (c) Any three from: – large monitor/screen with hi-res – touch screen – plotter – space mouse/space ball/4D device – 3D glasses (in some applications) – light pen – graphics tablet – 3D printer – 3D scanner [3] 6 (a) Any two from: – webcam – speakers – microphone – broadband modem [2] (b) Any one from: – use of CODEC (converts/compresses analogue data into digital data) – echo cancellation s/ware (allows talking in real time/keeps everything in sync) – compression s/ware for video/audio – s/ware to access broadband/networking [1] (c) (i) Any one from: – immediate response to questions/queries – can see each other watch body language etc. – easier to have several participants (would be difficult using instant messaging if several people involved) – would take a long time typing out each question (ii) Any one from: – need for expensive equipment/high set up costs – sometimes synchronisation problems make it difficult for delegates – need to train people to use the new technology – greater use of bandwidth [2]

Page 5 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – October/November 2011 0420 11 © University of Cambridge International Examinations 2011 (d) Any one from: – faster communications now widely available – safety reasons, e.g. increase in terrorist attacks on international flights – reduced transportation/accommodation/hardware costs – environmental issues, e.g. reduced carbon footprint – increase in multinational working [1] 7 (i) number count temp total neg OUTPUT 7 1 0 0 2 –5 1 3 0 2 4 5 5 –4 3 6 0 4 7 10 8 –2 5 0, 5 < - - - - - 1 mark - - - - - - >< - - - - - 1 mark - - - - - ->< - - - - - 1 mark - - - - - -> (ii) number count temp total neg OUTPUT 6 1 0 0 2 21 21 3 20 41 4 30 71 5 19 6 21 92 7 15 92, 0 < - - - - - 1 mark - - - - - - >< - - - - - 1 mark - - - - - ->< - - - - - 1 mark - - - - - -> [6]

Page 6 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – October/November 2011 0420 11 © University of Cambridge International Examinations 2011 8 Any three from: – gather information from experts – design the knowledge base – create/enter data into the knowledge base – design/create the inference engine – design/create the rules base – develop the input interface/interrogation technique – test system fully with known outcomes – create structure to relate each item in the knowledge base – design method of displaying results – expert system shell [3] 9 (a) (i) = B2/C2 [1] (ii) = AVERAGE(D2:D7) OR = SUM(D2:D7)/6 OR = (D2 + D3 + D4 + D5 + D6 + D7)/6 [1] (iii) = MAX(D2:D7) [1] (b) D7, D8, D9 [2] (c) = (C7/B7) * 100 [2] 10 (a) Any two from: – available to those who don’t have an Internet connection – many people prefer the human contact – often better talking to a human/can develop query – faster response to a question once connected – easier to resolve more complex problems (can take user through steps to solution to problem) [2] (b) Any two from: – no need to wait in a queue – no problem with language/dialect/accent/culture differences – open 24-7/can leave question on website any time – customer can save/print solution for later referral – multimedia services available (e.g. ‘How to’ videos) [2] (c) Any two from: – job losses – de-skilling – need to (re-)train – more jobs for technical staff – possible job sharing/flexi-hours/working from home [2]

Page 7 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – October/November 2011 0420 11 © University of Cambridge International Examinations 2011 11 (a) (i) Any one from: – unit of data/memory – 8 bits – used to represent a character [1] (ii) Any one from: – 230 bytes – 1 073 741 824 bytes – 1 048 576 kilobytes – 1024 megabytes [1] (b) Any two from: Flash memory – magnetic media/solid state memory – no formatting issues – plugs directly into the USB port – direct transfer of data CD-RW – optical media – slower access speed/flash memory has faster access speed – requires a separate drive – data needs to be burnt/finalised/finished (before being used on another device) [2] 12 (a) Only answers: – temperature (sensor) – oxygen (sensor) [2] (b) Any four from: – information from the sensors sent to microprocessor – the ADC converts the analogue data into digital form – if temperature < 25ºC OR temperature checked against stored value – ...microprocessor sends signal to heater/actuator/valve... – ...to switch on heater – if oxygen level < 20 ppm OR oxygen level checked against stored value – ...to open valve/oxygen supply – use of DAC between microprocessor and devices – sounds an alarm if system unable to respond – continuously monitors sensor inputs – any reference to feedback [4] (c) Any one from: – unsafe limit stored in memory – warning sound/signal if too high a value reached – fail safe switch off in case of a malfunction [1]

Page 8 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – October/November 2011 0420 11 © University of Cambridge International Examinations 2011 13 (a) Any four from: – satellites transmit signals to onboard computers – computers receive/interpret these signals – system depends on very accurate timing/use of atomic clocks – each satellite transmits data indicating location and time – computer in aeroplane calculates location based on at least three satellites – at least 24 satellites in operation at any one time – position accurate to within one metre – can also calculate altitude of aeroplane – ref to “triangulation”: [4] (b) Any two from: – safer as known location is exact/more accurate – reduces possibility of pilot error – allows accurate estimation of arrival time – display and guide pilot to nearest airport in case of emergency [2] 14 (a) 1 mark for each correct logic gate: [6] satellite 1 satellite 2 exact location of aeroplane satellite 3 NOT NOT NOT P R T X AND AND OR OR

Page 9 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – October/November 2011 0420 11 © University of Cambridge International Examinations 2011 (b) P R T X 0 0 0 1 0 0 1 1 0 1 0 1 0 1 1 0 1 0 0 0 1 0 1 0 1 1 0 1 1 1 1 0 [4] 15 (a) 1 mark for the correct working in BOTH parts 1 mark for valid 1 mark for not valid (i) working = (4 × 6) + (2 × 5) + (1 × 4) + (9 × 3) + (2 × 2) + (3 × 1) = 24 + 10 + 4 + 27 + 4 + 3 = 72 ÷ 11 = 6 remainder 6 valid/not valid: NOT valid (ii) working = (8 × 6) + (2 × 5) + (0 × 4) + (1 × 3) + (5 × 2) + (6 × 1) = 48 + 10 + 0 + 3 + 10 + 6 = 77 ÷ 11 = 7 remainder 0 valid/not valid: VALID [3] (b) 1 mark for correct working + 1 mark for check digit working = (5 × 6) + (0 × 5) + (2 × 4) + (4 × 3) + (1 × 2) = 30 + 0 + 8 + 12 + 2 = 52 need to add 3 to make the total 55 (i.e. exactly divisible by 11) check digit: 3 [2] (c) 2 digits transposed (e.g. 280419 becomes 280149/ two digits have been switched) incorrect digit (e.g. 280419 becomes 250419/ one of the digits has been mistyped) [2] 1 mk 1 mk 1 mk 1 mk ] ] ] ]

Page 10 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – October/November 2011 0420 11 © University of Cambridge International Examinations 2011 16 (a) Any two from: – lock the room/computer – use/prevent use of removable storage media – passwords and/or ids (to get into the system) – log off when computer not attended – encrypt data [2] (b) 1 mark for each risk + 1 mark for associated protection method. risk: virus protection: use ant-virus software risk: hacking protection: passwords/ids firewalls risk: use of wifi systems protection: passwords/ids firewalls risk: phishing: protection: don’t open websites from “unknown” emails anti-phishing software risk: pharming: protection: check certification of website under properties check spelling of websites use a well respected ISP [4] (c) (i) [1] (ii) Any one from: – if one station/cable fails, others are not affected – easier to identify faults when using star topologies – it is easier to expand this type of network – performance doesn’t deteriorate under load [1]

Page 11 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – October/November 2011 0420 11 © University of Cambridge International Examinations 2011 (d) Any two from: – processor should consume as little power as possible (thus prolonging the battery life) – processor should run as cool as possible (minimising problems associated with heat dissipation) – no fans needed to cool processor (thus reducing the load on the internal battery) [2] 17 (a) marking points: the way to find and print the largest value a 1 mark the way to find and print the largest value b 1 mark the way to find and print the largest value c 1 mark sample algorithm: input a, b, c if a > b and a > c then print a (1 mark) else if b > c then print b (1 mark) else print c (1 mark) [3] (b) marking points: loop construct 1 mark check if number is an integer 1 mark counting the number of integers input 1 mark output count value (outside the loop) 1 mark sample algorithm: for x = 1 to 1000 (1 mark) input number difference = INT(number) – number (1 mark) if difference = 0 then total = total + 1 (1 mark) next x print total (1 mark) (NOTE: alternative to lines 3 and 4: if INT(number) = number then total = total + 1 (2 marks) ) [4]