Cambridge IGCSE Computer Studies 0420 — 2011 Oct/Nov Paper 1 · Variant 3

This document consists of 20 printed pages. IB11 11_0420_13/4RP © UCLES 2011 [Turn over *7243189671* For Examiner's Use UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS International General Certificate of Secondary Education COMPUTER STUDIES 0420/13 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 0420/13/O/N/11 For Examiner's Use 1 (a) Give two benefits of networking a set of computers. 1 2 [2] (b) A college decides to use network computers with wireless capability. Give one advantage and one disadvantage of using wireless systems. Advantage: Disadvantage: [2]

3 © UCLES 2011 0420/13/O/N/11 [Turn over For Examiner's Use 2 The following table shows three applications which require specialist output devices. For each application, suggest one possible output device and give a reason for your choice. Application Output device Reason for choice of device A visually impaired person using a word processor Using CAD to design a new engine Monitoring a house for burglars [6]

4 © UCLES 2011 0420/13/O/N/11 For Examiner's Use 3 A user wishes to use a word processing application. They can either use a command line interface (CLI) or a graphical user interface (GUI) to open this application. (a) Describe how both methods could be used to select the application including any input hardware needed. (i) CLI (ii) GUI [4] (b) (i) What is meant by automatic data capture? (ii) Name a device used in automatic data capture and describe an application that uses it. Device: Application: [3]

5 © UCLES 2011 0420/13/O/N/11 [Turn over For Examiner's Use 4 Five definitions and descriptions are shown below on the left hand side. Five computer terms are shown on the right. Match the definitions/descriptions on the left to the correct term on the right by drawing connecting arrows. check if students’ ages are in the range 11 to 18 verification computer generated operation of a chemical process validation software that looks for information based on certain key words simulation system where all the data are collected first before being processed in one go search engine typing in a password twice to ensure it is correct batch processing [5]

6 © UCLES 2011 0420/13/O/N/11 For Examiner's Use 5 When new software is produced it is usually accompanied by user documentation and technical documentation. (a) Explain these two terms: user documentation: technical documentation: [2] (b) The following list contains items that can be found in either or both types of documentation. Tick (
) the box which indicates where you would find each item. Item User documentation only Technical documentation only Both user and technical documentation how to save a file program listing/coding hardware and software requirements file structures list of variables how to load the software meaning of errors/error messages [3]

7 © UCLES 2011 0420/13/O/N/11 [Turn over For Examiner's Use 6 (a) What is meant by the term web browser? [1] (b) Rock-ICT has set up a website as shown below: ROCK – ICT Home Sales Basket Checkout Payment Choose your payment method: credit card debit card click here to go to CD website (i) (ii) (iii) Give the names of the three parts that have been labelled: (i) (ii) (iii) [3] (c) How does the website recognise the user’s buying preferences as soon as they visit the website? [1] (d) Hacking is one security issue associated with the Internet and emails. State two other security issues. 1 2 [2]

8 © UCLES 2011 0420/13/O/N/11 For Examiner's Use 7 The following flowchart inputs the size of a number of car engines; a value of -1 stops the input. The following information is output: average engine size and number of engines with size > 1.5. START STOP engine = 0: count = 0: number = 0 INPUT size is size = –1 ? is size > 1.5 ? OUTPUT average, count number = number + 1 engine = engine + size average = engine/number count = count + 1 No No Yes Yes

9 © UCLES 2011 0420/13/O/N/11 [Turn over For Examiner's Use Complete the trace table for the following input data: 1.8, 2.0, 1.0, 1.3, 1.0, 2.5, 2.0, 1.3, 1.8, 1.3, -1 engine count number size average OUTPUT [6]

10 © UCLES 2011 0420/13/O/N/11 For Examiner's Use 8 Robots are being introduced into a factory which makes engines. (a) Describe three ways this could affect the workers. 1 2 3 [3] (b) One of the many advantages to management is the reduction in overall costs. Give two reasons why using robots could reduce costs. 1 2 [2] (c) Give two other advantages to the management of introducing robots. 1 2 [2]

11 © UCLES 2011 0420/13/O/N/11 [Turn over For Examiner's Use 9 A spreadsheet was set up to compare passenger costs for five airlines. A B C D E 1 Flight id Distance (km) Number of passengers Total revenue ($) Cost per passenger ($) 2 AA 151 3 000 240 60 000 250 3 AT 304 2 000 320 80 000 250 4 BR 106 1 500 150 45 000 300 5 CD 221 8 000 400 360 000 900 6 EX 115 6 000 280 140 000 500 7 Average cost: (a) What formula must be in E2 to calculate the cost per passenger. [1] (b) Cell E7 is to contain the average passenger cost. What formula would need to be placed in this cell? [1] (c) It was decided to add two new columns (F and G) to find out if the airline made a profit or loss on each flight. The costs per flight are calculated by multiplying Distance (km) by 1/10th of the Number of passengers. (i) What formulas must be in column F? F 1 Flight costs ($) 2 3 4 5 6 [2] (ii) The formula = IF (F2 > D2, “Loss”, “Profit”) was added to cell G2. What would be output? [1] (iii) What formula would be in G5 after replication down from G2? [1]

12 © UCLES 2011 0420/13/O/N/11 For Examiner's Use 10 A computer system is being used to monitor and control a chemical process. chemical process valve gases in gases out computer pressure sensor temperature sensor heater (a) Data are collected from sensors at regular intervals and compared with stored values. (i) Describe how the computer uses this data when monitoring the chemical process. [1] (ii) Describe how the computer uses this data when controlling the chemical process. [1]

13 © UCLES 2011 0420/13/O/N/11 [Turn over For Examiner's Use (b) What steps are necessary for the computer to control the temperature of the chemical process? [3] (c) Name two other sensors and give a different application where they are used. sensor 1: application: sensor 2: application: [4]

14 © UCLES 2011 0420/13/O/N/11 For Examiner's Use 11 A digital alarm clock is controlled by a microprocessor. It uses the 24-hour clock system (i.e. 6 pm is 18:00). Each digit in a typical display is represented by a 4-digit binary code: 8 4 2 1 0 1st digit (0) 0 0 0 1 2nd digit (8) 0 0 0 0 3rd digit (3) 0 1 1 0 4th digit (5) 1 0 1 is represented by: For example: (clock display) (a) What time is shown on the clock display if the 4-digit binary codes are: 8 4 2 1 0 0 0 1 0 1 1 0 0 1 0 0 1 0 0 1 (clock display) [2] (b) What would be stored in the 4-digit binary codes if the clock display time was: 8 4 2 1 1st digit 2nd digit 3rd digit 4th digit [4]

15 © UCLES 2011 0420/13/O/N/11 [Turn over For Examiner's Use (c) The clock alarm has been set at 08:00. Describe the actions of the microprocessor which enable the alarm to sound at 08:00. [2]

16 © UCLES 2011 0420/13/O/N/11 For Examiner's Use 12 A database has been set up to show details about countries. Part of the database is shown below. Country code Country Continent Area (millions sq km) Population (millions) Coastline Currency CH China Asia 9.6 1320 Yes yuan IN India Asia 3.8 1150 Yes rupee PO Poland Europe 0.3 39 Yes zloty BO Bolivia America 1.1 9 No boliviano TI Tibet Asia 1.2 2 No yuan BR Brazil America 8.5 192 Yes real RO Romania Europe 0.2 22 No leu SA Saudi Arabia Asia 2.2 28 Yes riyal ZA Zambia Africa 0.7 12 No kwacha (a) How many fields are in each record? [1] (b) Using Country code only, what would be output if the following search condition was used? (Population (millions) > 1000) OR (Continent = “Asia”) [2] (c) Write down a search condition to find which countries have a land area less than 3 million square km and also have a coastline. [2] (d) If the database was sorted in descending order of population size, using Country code only, what would be the order of countries in the database? [2]

17 © UCLES 2011 0420/13/O/N/11 [Turn over For Examiner's Use 13 The following flowchart shows how barcodes are used when a customer buys items from the supermarket. Barcodes are used to find the prices and to carry out stock control. Several stages are missing from the flowchart. These stages are shown in the item list below. Insert the correct statements, using numbers only, to complete the flowchart. [5] START STOP 1 any more items to scan? 2 decrease stock level by 1 3 key in barcode number manually 4 print “error” 5 print out the order form 6 print out the itemised bill 7 get price and display item price 8 scan in coupons, loyalty cards, etc 9 has stock already been ordered? 10 is stock <= minimum stock level? 11 customer makes payment List of statements No. No No Yes Yes Yes Yes No No No Yes scan in the next barcode has barcode been found? has barcode been found?

18 © UCLES 2011 0420/13/O/N/11 For Examiner's Use 14 An alarm, Y, sends a signal (Y = 1) when certain fault conditions in a chemical process are detected. The inputs are: Input Binary value Condition 1 acidity > 5 A 0 acidity <= 5 1 temperature >= 120UC T 0 temperature < 120UC 1 stirrer bar ON S 0 stirrer bar OFF The alarm, Y, returns a value of 1 if: either (i) temperature >= 120UC AND stirrer bar is OFF or (ii) acidity > 5 AND temperature < 120UC (a) Draw the logic circuit for the above system using these logic gates. AND NOT OR [5]

19 © UCLES 2011 0420/13/O/N/11 [Turn over For Examiner's Use (b) Complete the truth table for this alarm system. A T S Y 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] 15 A student gave the following three computer definitions. Give the name of the term being described in each case. (i) “a signal from a device sent to a computer causing the CPU to stop its current operation temporarily” (ii) “an exchange of signals between two devices when communicating to ensure synchronisation” (iii) “a temporary memory to store data waiting to be sent to a device” [3]

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 0420/13/O/N/11 For Examiner's Use 16 The weather conditions in a town are being monitored over a year (365 days). The values recorded per day are weather type and temperature (e.g. CLOUDY, 25) Write an algorithm, using pseudocode or flowchart only, which: • inputs the weather type and temperature for each day • outputs the number of days that were CLOUDY, RAINING, SUNNY or FOGGY • outputs the highest recorded temperature for the year • outputs the lowest recorded temperature for the year [6]

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 0420/13 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 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 13 © University of Cambridge International Examinations 2011 1 (a) Any two from: – share resources (hardware and software) – easier communications are possible – possible to work from any work station and access files/data – central data source – easier to control/monitor what users are doing – easier to ‘globally’ protect against unauthorised access [2] (b) Any one advantage and any one disadvantage from: Advantages – no trailing wires (therefore safer, less expensive since no cables) – allows users to work anywhere (portability) – can set up network in places where cable runs are not possible (e.g. outside, historic buildings etc.) Disadvantages – limited range – certain items (like filing cabinets) can block the signals – possible to ‘tap’ into WiFi if it isn’t secure – often slower data transfer rate than a wired system – needs additional hardware – number of access points need to match computers [2] 2 1 mark per point (max of 2 marks per application) Application Output device Reason for choice of device A disabled person using a word processor – speakers – Braille printers – allows blind people to hear output from word processors – blind people can read printed output Using CAD to design a new engine – plotter – large monitor – 3D printer – accurate print out of large drawings – allows easy editing of drawings – produce working prototypes in resin Monitoring a house for burglars – buzzer – light – alarm – to warn of intruder’s presence in the building [6]

Page 3 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – October/November 2011 0420 13 © University of Cambridge International Examinations 2011 3 (a) 1 mark for each description + 1 mark for each example of h/ware CLI description – user communicates by typing in commands (in response to a prompt) – several commands are entered to carry out a task (such as loading software) CLI h/ware – keyboard – keypad GUI description – user interacts with a computer using pictures and symbols (icons)/drop-down menu – tasks are initiated by selecting the icon – usually part of a windows/wimp environment GUI h/ware – pointing device (e.g. mouse) – touch screen [4] (b) (i) – saving/collecting data with no actual need for human interaction (ii) 1 mark for named device + 1 mark for matching application: if device is wrong then no application mark Device Application – barcode reader used in automatic stock control – document scanner transferring printed documents into an electronic form for storage on computer – mag stripe reader electronic funds transfer/entry through ‘locks’ – microphone part of voice recognition – automatically picking up sounds in burglar detection – OCR/OMR/MICR transferring documents to computer, reading multiple choice answers in a survey, reading cheques – RFID tracking animals/people/items/vehicles – retina scan/finger prints security systems – video camera security surveillance – correct sensor control applications – data logger used to monitor a parameter in an experiment [3]

Page 4 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – October/November 2011 0420 13 © University of Cambridge International Examinations 2011 4 1 mark per correct match [5] 5 (a) user documentation: – helps users learn how to use/operate the software technical documentation – designed to help programmers to make improvements to the system – helps programmers to repair/maintain the system [2] check if student’s ages are in the range 11 to 18 computer generated operation of a chemical process software that looks for information based on certain key words system where all the data is first collected before being processed in one go Typing in a password twice to ensure it is correct verification validation simulation search engine batch processing

Page 5 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – October/November 2011 0420 13 © University of Cambridge International Examinations 2011 (b) 1 mark for 3 correct answers, 2 marks for 4 to 6 correct answers and 3 marks if all 7 answers correct. Item User documentation only Technical documentation only Both user and technical documentation how to save a file √ program listing/coding √ hardware and software requirements √ file structures √ list of variables √ how to load the software √ meaning of errors/error messages √ [3] 6 (a) – program/software that allows a user to display web pages, web sites, etc. NOT access the Internet [1] (b) (i) webpage (part of) (ii) radio button (iii) hyperlink NOT link [3] (c) reference to cookies or description of cookie [1] (d) Any two from: – phishing – pharming – viruses – key logging or malware – spyware [2] Rationale: fishing and farming not acceptable

Page 6 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – October/November 2011 0420 13 © University of Cambridge International Examinations 2011 7 engine count number size average OUTPUT 0 0 0 1.8 1.8 1 1 2.0 3.8 2 2 1.0 4.8 3 1.3 6.1 4 1.0 7.1 3 5 2.5 9.6 6 2.0 11.6 4 7 1.3 12.9 5 8 1.8 14.7 9 1.3 16.0 10 (–1) 1.6 1.6, 5 (1mk) (1 mk) (1 mk) (1 mk) (1 mk) (1 mk) [6] 8 (a) Any three from: – unemployment – need to re-train – cleaner/less noisy environment – safer environment – possible de-skilling – less heavy lifting – reskilling with description – redeployment (could lead to new employment e.g. maintaining robots) [3] (b) Any two from: – less lighting/heating/air con costs since few people now in factory – no need to pay wages/salary – greater productivity (therefore lower unit cost) – can work non-stop/24-7 (no breaks/holiday) [2] (c) Any two from: – more consistent product – can work non-stop (no breaks, holidays, etc.)/24-7 – don’t go on strike – can be used in a dangerous environment – greater productivity [2]

Page 7 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – October/November 2011 0420 13 © University of Cambridge International Examinations 2011 9 (a) = D2/C2 [1] (b) = AVERAGE(E2:E6) OR = SUM(E2:E6)/5 OR = (E2 + E3 + E4 + E5 + E6)/5 [1] (c) (i) 1 mark for formula in F2 and 1 mark for all other formulas correct F 1 Flight costs ($) 2 = B2 * C2/10 3 = B3 * C3/10 4 = B4 * C4/10 5 = B5 * C5/10 6 = B6 * C6/10 [2] (ii) Loss [1] (iii) = IF (F5 > D5, “Loss”, “Profit”) [1] 10 (a) Any two from: (i) monitoring – decide if the temperature/pressure are out of range – give a warning if out of range/doesn’t change the process parameters [1] (ii) control – send signal to open/close valve, switch on/off a heater etc. – output affects the input [1] (b) Any three from: – data from temperature/pressure sensor… – …changed into digital by ADC – data is sent to computer – data/input is compared to values in memory – if temperature too low, signal sent to heater… – if pressure too low, signal sent to valve… – and heater turned on/valve opened – use of DAC – use of actuators – monitoring/control system continues to loop indefinitely [3]

Page 8 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – October/November 2011 0420 13 © University of Cambridge International Examinations 2011 (c) 1 mark for each sensor + 1 mark for each related application sensor application – light greenhouse environment open/close automatic doors – sound burglar alarm listening for sounds in pipes etc. – infra red burglar alarm detecting people (e.g. entering a building) – moisture greenhouse environment check if clothes dry in a drier – gas detection of gas leaks – pH soil acidity in greenhouse – smoke in buildings for fire detection – motion sensor/accelerometer vibrations in machinery – proximity parking cars [4] 11 (a) 1 6 : 4 9 1 mk 1 mk [2] (b) 0 0 0 1 1st digit 0 1 1 1 2nd digit 0 0 1 0 3rd digit 1 0 0 1 4th digit [4] (c) Any two from: – microprocessor compares present time with stored time – if the values are the same – sends signal to sound alarm [2] 12 (a) 7 [1] (b) CH, IN, TI, SA [2] (c) (Area (millions sq km) < 3) AND (Coastline = “Yes”) < - - - - - - - 1 mark - - - - - - ->< - - - - - - 1 mark - - - - - - > OR (Coastline = “Yes”) AND (Area (millions sq km) < 3) < - - - 1 mark - - - - >< - - - - - - - - 1 mark - - - - - - - - - > [2] (d) CH, IN, BR, PO, SA, RO, ZA, BO, TI [2]

Page 9 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – October/November 2011 0420 13 © University of Cambridge International Examinations 2011 13 START scan in the next barcode has bar code been found? 7/2 2/7 10 9 1 Has bar code been found? 3 4 5 8/11 11/8 6 STOP No Yes No Yes Yes No No Yes Yes No [5] (1 mark) (1 mark) (1 mark) (1 mark) (1 mark)

Page 10 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – October/November 2011 0420 13 © University of Cambridge International Examinations 2011 14 (a) 1 mark for each logic gate: [5] (b) A T S Y 0 0 0 0 0 0 1 0 0 1 0 1 } 0 1 1 0 1 0 0 1 1 0 1 1 1 1 0 1 1 1 1 0 [4] 15 (i) interrupt (ii) handshaking (iii) buffer [3] AND AND NOT NOT A T S Y 1 mk 1 mk 1 mk 1 mk ] ] ] ] OR

Page 11 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – October/November 2011 0420 13 © University of Cambridge International Examinations 2011 16 Marking points initialise variables 1 mark correct loop control 1 mark input (in correct place) 1 mark correct check on type of weather (if, case, etc.) 1 mark adding number of days of each type of weather 1 mark check for the highest temperature 1 mark check for the lowest temperature 1 mark output (all items in the correct place) 1 mark Sample algorithm c = 0: r = 0: s = 0: f = 0 high = 0 (or a negative number) low = 1000 (1 mark) for x = 1 to 365 (1 mark) input weather, temp (1 mark) if weather = “CLOUDY” then c = c + 1 else if weather = “RAINING” then r = r + 1 (2 marks) else if weather = “SUNNY” then s = s + 1 else if weather = “FOGGY” then f = f + 1 endif if temp > high then high = temp (1 mark) if temp < low then low = temp (1 mark) next x print c, r, s, f, high, low (1 mark) [6]