Cambridge IGCSE Computer Studies 0420 — 2013 May/June Paper 1 · Variant 2

This document consists of 20 printed pages. IB13 06_0420_12/3RP © UCLES 2013 [Turn over *0765126764* For Examiner's Use UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS International General Certificate of Secondary Education COMPUTER STUDIES 0420/12 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 0420/12/M/J/13 For Examiner's Use 1 (a) State two items found in typical technical documentation. 1 2 [2] (b) State two items found in a typical user guide. 1 2 [2] 2 Four types of data storage media and four descriptions are shown in the table below. Tick (
) the appropriate boxes in the table to match each data storage medium to its most suitable description. CD-ROM DVD-RAM fixed hard disk memory stick storage medium where data can only be read and not altered portable medium which allows transfer of data between computers memory where operating systems and applications software are usually stored medium which allows recording and playback to occur at the same time [4]

3 © UCLES 2013 0420/12/M/J/13 [Turn over For Examiner's Use 3 Three common devices are listed below: • MP3 player • digital camera • mobile phone (a) Choose one of the above devices. Describe the type of internal memory the device uses. Describe how data is transferred from the device to a computer. Device Type of internal memory used Method of transferring data to a computer [2] (b) Modern mobile phones include a digital camera and an MP3 player. (i) Give one disadvantage when compared to a dedicated MP3 player. (ii) Give one disadvantage when compared to a dedicated digital camera. [2]

4 © UCLES 2013 0420/12/M/J/13 For Examiner's Use 4 (a) Computer systems can introduce a number of health and safety issues in the office. Five potential risks are shown below. Indicate by ticking the appropriate column whether the risk is a health issue or a safety issue. potential risk health issue safety issue repetitive strain injury (RSI) caused by excessive clicking of a mouse or typing trailing wires connected to a computer system ozone gas and toner particles produced during laser printer operation headaches and eye strain caused by glare from a computer monitor/screen electrocution caused by spilling liquids on a computer system [5] (b) Introduction of computer systems can also have an impact on the workers in the office. Give three potential ways computers can affect the office workers. 1 2 3 [3]

5 © UCLES 2013 0420/12/M/J/13 [Turn over For Examiner's Use 5 Five definitions are given on the left hand side of the diagram below. Five computer terms are shown on the right. By drawing arrows, connect each definition to the correct computer term. website that allows virtual communication; user joins a site and invites friends who, in turn, invite their own friends chat room technology that allows telephone calls to be made using computer networks, such as the Internet social networking online “place” where a group of people get together and discuss a number of topics tagging software that allows any user to freely create and edit a web page using their own web browser VoIP marking, saving and archiving certain websites or items (such as photos); for example, it allows users to track and organise favourite websites or photos wiki [4]

6 © UCLES 2013 0420/12/M/J/13 For Examiner's Use 6 Five students made the following statements. Explain why each statement is incorrect. (a) “I always use CD-ROMs to save my data.” [1] (b) “The advantage of WiFi in the home is you don’t need the use of a telephone line connection.” [1] (c) “Satellite navigation systems in cars send signals to satellites so that the satellite can work out where they are.” [1] (d) “Sending an email will cause a problem if the recipient is in another time zone where the time difference is 12 hours.” [1] (e) “Video conferencing allows meetings to be called at any time.” [1]

7 © UCLES 2013 0420/12/M/J/13 [Turn over For Examiner's Use 7 The speed at which a CD spins in a portable music CD player is controlled by sensors and a small microprocessor. (a) Describe how the sensors and microprocessor are used to control the speed of the spinning CD. [4] (b) Sudden movements can make the CD “skip”. How can the microprocessor deal with this so that the CD operates correctly? [2] (c) Why would an MP3 player not suffer from the same problem? [1]

8 © UCLES 2013 0420/12/M/J/13 For Examiner's Use 8 Expert Systems are made up of a number of components. (a) The diagram below shows four of these components and four definitions. By drawing arrows, link the four components to their correct definitions: made up of a series of if … then statements called inference rules Inference Engine provides reasoning mechanism in a typical expert system Knowledge Base presents questions and information to a user and allows them to input a response Rules Base collection of facts used to solve problems in an expert system User Interface [3] (b) Describe three of the limitations associated with using Expert Systems. 1 2 3 [3]

9 © UCLES 2013 0420/12/M/J/13 [Turn over For Examiner's Use 9 Thin film technology is becoming increasingly common. This uses material as thin as a sheet of paper but which acts just like an LCD monitor. A microprocessor is used to control the device and solid state memories are used to supply the data. (a) Describe two advantages of thin film technology. 1 2 [2] (b) Describe two applications that could use thin film technology. 1 2 [2]

10 © UCLES 2013 0420/12/M/J/13 For Examiner's Use 10 A company uses an intranet which can also communicate with the outside world through the Internet. (a) The system uses modems. What is the purpose of a modem? [1] (b) Part of the company’s security strategy is to use a firewall. Describe two features of a firewall. 1 2 [2] (c) Connecting to the Internet can cause potential problems. State two of these problems. 1 2 [2]

11 © UCLES 2013 0420/12/M/J/13 [Turn over For Examiner's Use 11 A survey of motorways was carried out and a database was produced. A section of the database is shown below. Motorway ID Length (km) Cars per day Toll charge per km ($) Number of lanes M1 100 50 000 0.60 2 M2 210 75 000 0.40 3 M3 180 60 000 0.50 4 M4 40 20 000 0.30 3 M5 25 15 000 0.10 2 M6 100 40 000 0.70 4 M7 30 10 000 0.40 2 M8 150 60 000 0.60 4 (a) How many fields and how many records are shown? (i) number of fields (ii) number of records [2] (b) Using Motorway ID only, what would be output if the following search condition was used? (Length (km) > 100) AND (Number of lanes > 3) [1] (c) What search condition is needed to find the motorways where the number of cars per day exceeds 50 000 or the toll charge per kilometre is greater than $0.50? [2]

12 © UCLES 2013 0420/12/M/J/13 For Examiner's Use 12 Study the following flowchart very carefully. START END K = 0 X = 0 is A > B ? X = 0 K = A A = B B = K X = 1 OUTPUT A, B, C, D, E INPUT A, B, C, D, E Yes No is B > C ? K = B B = C C = K X = 1 Yes No is C > D ? K = C C = D D = K X = 1 Yes No is D > E ? K = D D = E E = K X = 1 is X = 1 ? Yes Yes No No

13 © UCLES 2013 0420/12/M/J/13 [Turn over For Examiner's Use (a) Complete the trace table for this flowchart using the following test data: 3, 5, 1, 4, 8 A B C D E K X [5] (b) What values are output from the flowchart using the above test data? [1] (c) What function is this flowchart carrying out? [1] (d) What would happen if the value of X wasn’t set to 0 in the return loop of the flowchart? [1]

14 © UCLES 2013 0420/12/M/J/13 For Examiner's Use 13 A company requests new customers who register online to give the following details: • name • address • type of credit/debit card • payment card number All details must be entered. (a) (i) Describe one suitable different validation check for each field. name address type of credit/debit card payment card number [4] (ii) Which of the four fields could be offered as a drop down box? Explain. [2]

15 © UCLES 2013 0420/12/M/J/13 [Turn over For Examiner's Use (b) Other data required: • date of birth • male or female • accept/decline company conditions Describe suitable input methods for this data. date of birth male or female accept/decline company conditions [3]

16 © UCLES 2013 0420/12/M/J/13 For Examiner's Use 14 Some decorative lights are made up from a cluster of red, blue, green, yellow and white LEDs. Each colour is represented by a binary code: 32 16 8 4 2 1 1 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0 1 red blue green yellow white black (all lights off) A 6-bit register, R1, stores the 1-values to represent a sequence of colours. Thus, if R1 contains: 0 1 0 1 0 1 this means the blue, yellow and black colour sequence is stored and displayed in that order. The length of time each light is on is set by a binary value in another register, R2: Thus 0 1 0 means each colour is on for 2 seconds. (a) The two registers contain the following values. What is the sequence of coloured lights and the timing for each colour? 1 1 1 0 R2 R1 1 1 0 1 0 sequence of colours timing [2]

17 © UCLES 2013 0420/12/M/J/13 [Turn over For Examiner's Use (b) What will the two registers contain if the coloured light sequence is red, green and black and the timing is 5 seconds? R2 R1 [2] (c) What is the problem with trying to display green, blue, red in that order? [2]

18 © UCLES 2013 0420/12/M/J/13 For Examiner's Use 15 (a) Draw the logic circuit represented by the logic statement: X = 1 if (B is NOT 1 AND S is NOT 1) OR (P is NOT 1 AND S is 1) B S X P [6] (b) Complete the truth table for the above logic statement. B S P 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]

19 © UCLES 2013 0420/12/M/J/13 [Turn over For Examiner's Use 16 A large word processor is being developed by first writing a series of modules. These are then put together to form the final word processor. Testing is done on each module and on the final word processor. The following flowchart shows how this word processor is developed. Several of the stages have been omitted. Complete the flowchart, using item number only, from the list of items given. START END WRITE the module Yes No Yes No No Yes Item Number Item Description 1 any errors in the module? 2 any more modules to write and test? 3 combine all modules to form final word processor 4 does final word processor give expected results? 5 modify final word processor 6 modify the module 7 test module using data with known outcomes 8 test final word processor using data with known outcomes 9 write user documentation ITEM LIST [5]

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 0420/12/M/J/13 For Examiner's Use 17 A country has four mobile phone network operators. Each mobile phone number has eight digits. The first three digits identify the network operator: 444 Yodafone 555 N2 network 666 Kofee mobile 777 Satsuma mobile Write an algorithm, using pseudocode or flowchart only, which reads 50 000 eight-digit mobile phone calls made during the day and outputs the number of calls made on each of the four networks. [6]

CAMBRIDGE INTERNATIONAL EXAMINATIONS International General Certificate of Secondary Education MARK SCHEME for the May/June 2013 series 0420 COMPUTER STUDIES 0420/12 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 12 © Cambridge International Examinations 2013 1 (a) Any two items from the list: purpose of the system/program/software/package program listing/coding programming language used flowcharts/algorithms/pseudocode screen (input) formats/layouts hardware requirements software requirements (minimum) memory requirements known bugs list of variables (and their meaning)/data dictionary file structures sample runs output formats/layouts validation rules meaning of error messages installation guide [2] (b) Any two items from the list: purpose of the system/program/software/package how to log in/log out how to load/run software how to save/load files how to do a search how to sort data how to print (out documents/files) how to delete/add/amend records screen (input) formats/layouts output formats/layouts hardware requirements software requirements sample runs meaning of error messages troubleshooting/help/FAQs tutorials installation guide [2]

Page 3 Mark Scheme Syllabus Paper IGCSE – May/June 2013 0420 12 © Cambridge International Examinations 2013 2 1 mark for each correctly identified use of data storage medium (column): CD-ROM DVD-RAM fixed hard disk memory stick storage medium where data can only be read and not altered
portable medium which allows transfer of data between computers
memory where operating systems and applications software are usually stored
medium which allows recording and playback to occur at the same time
[4]

Page 4 Mark Scheme Syllabus Paper IGCSE – May/June 2013 0420 12 © Cambridge International Examinations 2013 3 (a) 1 mark for type of memory used and 1 mark for data transfer method. chosen device type of internal memory method of transferring data MP3 player – (NAND) flash memory – solid state memory – type of EEPROM – non-volatile memory – SD card – using USB (port/cable) in computer – blue tooth/WiFi connection – slot card into computer card reader digital camera – (NAND) flash memory – solid state memory – type of EEPROM – non-volatile memory – SD card or XD card – using USB (port/cable) in computer – blue tooth/WiFi connection – slot card into computer card reader mobile phone – (NAND) flash memory – solid state memory – type of EEPROM – non-volatile memory – SD card – using USB (port/cable) in computer – blue tooth/WiFi connection – slot card into computer card reader [2] (b) (i) Any one disadvantage from: – memory size in mobile phone is usually much smaller – many MP3 features (e.g. shuffle) not available on the mobile phone – track/song can be interrupted by an incoming call on a mobile phone [1] (ii) Any one disadvantage from: – poorer quality of image due to phone’s inferior camera lens/fewer pixels /lower resolution – stores fewer pictures – fewer photographic options [1]

Page 5 Mark Scheme Syllabus Paper IGCSE – May/June 2013 0420 12 © Cambridge International Examinations 2013 4 (a) 1 mark for each correct health and safety risk identified: potential risk health issue safety issue repetitive strain injury (RSI) caused by excessive clicking of a mouse or typing
trailing wires connected to a computer system
ozone gas and toner particles produced during laser printer operation
headaches and eye strain caused by glare from a computer monitor/screen
electrocution risk caused by spilling liquids on a computer system
[5] (b) Any three from: – loss of work/unemployment – de-skilling of workers – need for workers to re-train – can work from home/remote working – use of video conferencing rather than face to face meetings – quieter environment in the office – more use of “out sourcing” of work (workers become project managers) – use of computer for non-work related activities (accept an example of this) [3]

Page 6 Mark Scheme Syllabus Paper IGCSE – May/June 2013 0420 12 © Cambridge International Examinations 2013 5 [4] website that allows virtual communication; user joins a site and invites friends who, in turn, invite their own friends technology that allows telephone calls to be made using computer networks, such as the Internet on line “place” where a group of people get together and discuss a number of topics server software that allows any user to freely create and edit a web page using their own web browser marking, saving and archiving certain web sites or items (such as photos); it allows users to track and organise favourite web sites and, for example, photos chat room social networking tagging VoIP wiki

Page 7 Mark Scheme Syllabus Paper IGCSE – May/June 2013 0420 12 © Cambridge International Examinations 2013 6 (a) Any one from: – not possible to save data on a CD-ROM – CD-ROMs are read only – data cannot be altered on a CD-ROM [1] (b) Any one from: – WiFi only connects devices together in the home/connects to router – still need Internet external connection via telephone network/wires [1] (c) Any one from: – satellites send signals TO (the GPS system in) the car (sat nav) – GPS device and NOT the satellite works out the cars’ location [1] (d) Any one from: – Messages left in the inbox/stored on server – and then opens it/reads message at their leisure [1] (e) Any one from: – not true since time zones/differences prevent this – meetings can be held at short notice (which is very different) [1]

Page 8 Mark Scheme Syllabus Paper IGCSE – May/June 2013 0420 12 © Cambridge International Examinations 2013 7 (a) Any four points from: – (light) sensor sends data signals about spinning CD to microprocessor – the signals/data are converted from analogue to digital (by an ADC) – microprocessor uses data and “counts” number of CD revolutions per second/calculates speed of revolution – this calculated/received value is compared to the value stored in memory – if the number of revolutions/speed is out of acceptable range microprocessor sends a signal … – … and the CD speed is increased/decreased accordingly – an error message is also sent if the speed is out of range [4] (b) Any two points from: – sensors indicate sudden jolt/movement – data from CD stored in a temporary memory/buffer – there is a (2 to 4 second) delay in “real time” playback – playback is suspended until device is stable again [2] (c) Any one from: – no moving parts e.g. no spinning CDs, solid state – no “physical” media [1]

Page 9 Mark Scheme Syllabus Paper IGCSE – May/June 2013 0420 12 © Cambridge International Examinations 2013 8 (a) [3] (b) Any three from: – lack human common sense – cannot make creative responses in unusual/new circumstances – can’t always explain clearly their logic and reasoning – lack a degree of flexibility – not able to recognize when no answer is actually available – do not learn unless the knowledge base/expert system is updated – only give percentage probability that answer could be correct [3] made up of a series of if … then statements called inference rules provides reasoning mechanism in a typical expert system presents questions and information to a user and allows them to input a response collection of facts and rules used to solve problems in an expert system Inference Engine Knowledge Base Rules Base User Interface

Page 10 Mark Scheme Syllabus Paper IGCSE – May/June 2013 0420 12 © Cambridge International Examinations 2013 9 (a) Any two from: – can put the film anywhere (e.g. stick on a curved wall) – can fit to awkward shapes where rigid screen would be impossible – can be any size required – self-contained unit – use less energy – less physical space required [2] (b) Any two from: – advertising (e.g. in railway stations, airports, etc.) – books/magazines/newspapers made out of the thin film – art (i.e. moving pictures, light shows, etc.) – any screen application e.g. TV, mobile phone etc. [2] 10 (a) Any one from: – allows digital systems to use analogue phone networks – convert analogue – digital – analogue – digital signal converted from one form to another (for transmission) [1] (b) Any two from: – blocks unauthorized external users gaining access to the intranet – blocks programs/software gaining access to Internet from intranet – filters out certain websites to users of intranet when accessing the Internet – aids/helps to prevent viruses – packet inspection/traffic flow monitoring [2] (c) Any two from: – hacking – viruses/malware – security issues (pharming, phishing, spyware, etc.) – access to undesirable web sites – abuse of computer time by work force [2]

Page 11 Mark Scheme Syllabus Paper IGCSE – May/June 2013 0420 12 © Cambridge International Examinations 2013 11 (a) (i) 5 [1] (ii) 8 [1] (b) M3 and M8 only [1] (c) (Cars per day > 50 000) OR (Toll charge per km ($) > 0.50) < - - - - - (1 mark) - - - - > < - - - - - - - - - (1 mark) - - - - - - - - - -> Or (Toll charge per km ($) > 0.50) OR (Cars per day > 50 000) < - - - - - - - (1 mark) - - - - - - - > < - - - - - - - (1 mark) - - - - - - -> [2]

Page 12 Mark Scheme Syllabus Paper IGCSE – May/June 2013 0420 12 © Cambridge International Examinations 2013 12 (a) a A B C D E K X 3 5 1 4 8 0 0 5 3 3 1 4 1 1 1 8 1 1 1 0 4 3 3 1 8 3 3 1 0 8 4 4 1 0 8 5 5 1 0 < - - - - 1 mark - - - - >< 1 mark >< - - - - 1 mark - - - - > < 1 mark >< 1 mark > [5] (b) 8, 5, 4, 3, 1 [1] (c) SORT/ORDER (descending) routine [1] (d) – would continue looping round even when sorting complete – loop would never end/infinite loop [1]

Page 13 Mark Scheme Syllabus Paper IGCSE – May/June 2013 0420 12 © Cambridge International Examinations 2013 13 (a) (i) name: – character/type check – presence check address: – character/type check – presence check – use lookup file/database type of card: – character/type check – presence check – consistency check – format check card number: – length check – format check – check digit – range check – character/type check – presence check (need different validation check for each item) [4] (ii) – type of credit/debit card – limited number of possible options [2] (b) date of birth – drop down boxes of day, month and year – use of input boxes: – calendar object male or female – radio buttons – tick/check boxes – drop down/combo box accept/decline company conditions – tick/check boxes – radio buttons – drop down/combo box [3]

Page 14 Mark Scheme Syllabus Paper IGCSE – May/June 2013 0420 12 © Cambridge International Examinations 2013 14 (a) sequence of colours is: blue green white time delay is: 7 seconds [2] (b) <- - - - - - - 1 mark - - - - - - -> <- - 1 mark - -> [2] (c) – sequence always starts from left to right – so sequence would still be red, blue then green [2] 1 0 1 0 0 1 1 0 1

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Page 16 Mark Scheme Syllabus Paper IGCSE – May/June 2013 0420 12 © Cambridge International Examinations 2013 16 [5] START WRITE the module 7 1 2 6 3 8 4 5 9 END Yes No No Yes No Yes 1 mark 1 mark 1 mark 1 mark 1 mark

Page 17 Mark Scheme Syllabus Paper IGCSE – May/June 2013 0420 12 © Cambridge International Examinations 2013 17 marking points: – initialisation of all the variables 1 mark – corrects loop (1 to 50 000) 1 mark – input number (INSIDE a loop) 1 mark – how to identify the first 3 digits in the input number 1 mark – test which of the 4 networks number comes from 1 mark – increment appropriate network total (INSIDE a loop) 1 mark – addition of some form of error checking 1 mark – output totals (OUTSIDE the loop) 1 mark sample coding: Y = 0: N = 0: K = 0: S = 0 1 mark for count = 1 to 50 000 1 mark input number 1 mark X = number/100 000 000 1 mark if X > 0.7 then S = S + 1 } else if X > 0.6 then K = K + 1 } 2 else if X > 0.5 then N = N + 1 } marks else if X > 0.4 then Y = Y + 1 } else print “error in number” 1 mark next count print Y, N, K, S 1 mark [6]