Cambridge IGCSE Computer Studies 0420 — 2013 Oct/Nov Paper 1 · Variant 2

This document consists of 20 printed pages. IB13 11_0420_12/FP © UCLES 2013 [Turn over *8580267993* For Examiner's Use UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS International General Certificate of Secondary Education COMPUTER STUDIES 0420/12 Paper 1 October/November 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/O/N/13 For Examiner's Use 1 Internet security is a major issue for many people. The following is a list of five typical security issues: • hacking • pharming • phishing • spyware • viruses Choose three of these security issues. For each one, describe the security issue and suggest a way of protecting against it. Security issue 1 Description of issue Method of protection Security issue 2 Description of issue Method of protection Security issue 3 Description of issue Method of protection [6]

3 © UCLES 2013 0420/12/O/N/13 [Turn over For Examiner's Use 2 (a) Mobile phones are communication devices. They allow communication via speech or text messaging. (i) Most mobile phones offer predictive texting. State what is meant by this term. [1] (ii) What two additional functions would you expect to find on a mobile phone? 1 2 [2] (b) Connecting a USB telephone to a computer allows communication using VoIP technology. (i) Give one advantage of using VoIP rather than other telephone systems. (ii) Give one disadvantage of using VoIP rather than other telephone systems. (iii) To use VoIP, there is no need to use a USB telephone. What other hardware could be used to allow verbal communications? [3]

4 © UCLES 2013 0420/12/O/N/13 For Examiner's Use 3 A motor car manufacturer offers various combinations of • seat colours • seat materials • car paint colours A database was set up to help customers choose which seat and paint combinations were possible. seat material car paint colours code cloth leather seat colour white red black blue green silver grey CB Y N black Y Y Y Y Y Y Y LB N Y black N Y N N N Y Y CC Y N cream N Y Y Y N N N LC N Y cream N Y Y Y N N Y CG Y N grey N Y Y Y Y Y N LG N Y grey N Y N Y N Y Y CR Y N red Y N Y N N Y Y LR N Y red Y N Y N N Y Y CL Y N lime N N N Y N N N LL N Y lime N N Y Y Y N N (NOTE: N = no, not a possible combination, Y = yes, combination is possible) (a) How many records are shown in the database? [1] (b) The following search condition was entered: (cloth = “Y”) AND (blue = “Y”) Using code only, which records will be found? [2] (c) A customer wanted to know the possible combinations for a car with leather seats and either silver or grey paint colour. What search condition would need to be input? [2]

5 © UCLES 2013 0420/12/O/N/13 [Turn over For Examiner's Use (d) A customer decided to buy a green car. He wanted to know which seat colours and seat materials were not a possible combination with green paint. What search condition would he need to enter? [1] (e) Give one advantage of using the codes Y and N in the database rather than using Yes and No. [1] 4 (a) Seven hardware items are shown on the right hand side in the diagram below. Three applications are shown on the left in the diagram. By drawing arrows, link each application to the appropriate hardware items (each hardware item must be used once only): speakers computer aided design (CAD) light pen microphone video conferencing spaceball data goggles virtual reality webcam data gloves [3] (b) Name one additional item of hardware used in each of the three applications named in the above diagram. CAD video conferencing virtual reality [3]

6 © UCLES 2013 0420/12/O/N/13 For Examiner's Use 5 Study the following flowchart very carefully. START count = 1 total = 0 x = a * 3 + c * 3 y = b * 2 + d * 2 total = x + y temp = total temp = temp - 10 is temp < 10? count = count + 1 INPUT a, b, c, d OUTPUT temp is count <= 2? END No Yes Yes No

7 © UCLES 2013 0420/12/O/N/13 [Turn over For Examiner's Use Complete the trace table for the following two sets of data: (i) a = 5, b = 4, c = 1, d = 9 (ii) a = 5, b = 9, c = 4, d = 1 count total a b c d x y temp OUTPUT [6]

8 © UCLES 2013 0420/12/O/N/13 For Examiner's Use 6 A spreadsheet was set up to calculate values of v based on the formula: v = u + a * t A B C D 1 value of u value of a value of t result v 2 20 9.81 10 3 10 9.81 20 4 30 9.81 40 5 40 9.81 30 6 50 9.81 20 7 20 9.81 50 8 (a) A student typed in = (D2 + B2 * C2) into cell D2. Why would this formula produce an error message? [1] (b) What is the correct formula that should be in cell D2? = [1] (c) If this formula was replicated down to cell D7, what formula would be in D7? = [1] (d) What formula is required in cell D8 to find the highest value of v? = [1] (e) Column B has the same value throughout. If column B was removed, what would be the new formula in D2? = [1]

9 © UCLES 2013 0420/12/O/N/13 [Turn over For Examiner's Use 7 A company employs staff who frequently use computer systems. (a) The health and safety of the staff when using computers is very important. (i) It was discovered that two staff were suffering from RSI in the hands and wrists. What could cause such problems? How could this health risk be removed or reduced? [2] (ii) Three accidents had been caused by staff tripping over wires in the office. How could this safety risk be removed? [1] (iii) Name another health and safety risk and describe what problem it might cause. Name of risk Description of problem [2] (b) Before the introduction of computers, the staff used to do all the office tasks (such as filing) manually. Describe two ways the introduction of computers might have affected the staff. 1 2 [2]

10 © UCLES 2013 0420/12/O/N/13 For Examiner's Use 8 A piece of pseudocode was written to input 1000 positive numbers and then output the highest and lowest numbers. 10 highest = 0 20 lowest = 0 30 for count = 1 to 100 40 input number 50 if number > highest then number = highest 60 if number < lowest then number = lowest 70 count = count + 1 80 next count 90 print highest, lowest There are errors in the code. Locate these errors and suggest a correction. Error 1 Correction Error 2 Correction Error 3 Correction

11 © UCLES 2013 0420/12/O/N/13 [Turn over For Examiner's Use Error 4 Correction [8] 9 Alex sends an email with a number of attachments to his friend, Nicola. Describe three possible problems Nicola might have when she tries to open these attachments. 1 2 3 [3]

12 © UCLES 2013 0420/12/O/N/13 For Examiner's Use 10 (a) (i) Complete the truth table for the following logic circuit which is made up of NOR gates only. A B X A B Working space X 0 0 0 1 1 0 1 1 [2] (ii) What single logic gate has the same function as the above circuit? [1]

13 © UCLES 2013 0420/12/O/N/13 [Turn over For Examiner's Use (b) Complete the truth table for the following logic circuit. A B C AND AND OR X NOT A B C 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]

14 © UCLES 2013 0420/12/O/N/13 For Examiner's Use 11 A denary number can be represented as an 8-bit binary number. For example: 27 would be represented as: 0 32 0 64 0 128 1 16 1 8 0 4 1 2 1 1 1 32 0 64 0 128 1 16 0 8 1 4 1 2 0 1 All the bits in the binary number have now been shifted (moved) one place to the left. (a) What denary number does this now represent? [1] (b) What effect did the shift have on the original denary number? [1] (c) If the above binary number was shifted another one place to the left, what denary number would it be equivalent to? [1] (d) (i) Represent the denary number 46 as an 8-bit binary number. 32 64 128 16 8 4 2 1 [1] (ii) Shift this 8-bit binary number 2 places to the left. What is the denary equivalent? [1] (iii) What problem would arise if you tried to shift this 8-bit binary number 3 places to the left? [1]

15 © UCLES 2013 0420/12/O/N/13 [Turn over For Examiner's Use (e) If any 8-bit binary number was shifted one place to the right, what would this be equivalent to? [1] 12 A shop uses an information screen linked to a computer to allow customers to order goods directly. The first screen shows three options: electrical goods furniture stationery (a) What is the best input device to allow customers to choose one of the three options? [1] (b) The customer is then sent to another screen where they have to input: • the goods reference number which is 8 digits long • today’s date which must be in the form dd/mm/yyyy • the customer’s telephone number For each input give one validation check that should be performed. A different type of check must be given in each case. goods reference number today’s date telephone number [3]

16 © UCLES 2013 0420/12/O/N/13 For Examiner's Use 13 A company advertises its Internet broadband speeds as follows: • download speed of 128 megabits per second • upload speed of 16 megabits per second (8 bits = 1 byte) (a) Explain what is meant by the two terms download speed and upload speed. download speed upload speed [2] (b) Give two advantages of using broadband rather than dial-up. 1 2 [2] (c) Give two different scenarios when a fast broadband connection is essential. 1 2 [2] (d) How many 4-megabyte files could be downloaded per second using this company’s broadband? [1]

17 © UCLES 2013 0420/12/O/N/13 [Turn over For Examiner's Use 14 An expert system has been developed to help diagnose faults in car engines. The software has been installed on a laptop computer. (a) Describe two desirable features to look for in a laptop rather than a desktop computer. 1 2 [2] (b) Part of the expert system is supplied on a memory stick. This needs to be plugged into a USB port for the expert system to work. Give one reason why this is done. [1] (c) Describe two features you would expect to see in the expert system’s interactive user interface. 1 2 [2] (d) Apart from the user interface, name three other components that make up a typical expert system. 1 2 3 [3]

18 © UCLES 2013 0420/12/O/N/13 For Examiner's Use 15 A library uses barcodes to identify borrowers and books. A borrower has a card containing a barcode with an equivalent numerical code. Each book also has a barcode with an equivalent numerical code. The flowchart on the facing page shows what happens when book(s) are taken out by a borrower. However, several stages are missing. Using item numbers only, complete the flowchart by selecting stages from the item list below. Item List Item Number Item Description 1 any more books to scan? 2 has book’s barcode been recognised? 3 has book’s numeric code been recognised? 4 has borrower’s barcode been recognised? 5 has borrower’s numeric code been recognised? 6 input book’s numeric code manually 7 input borrower’s numeric code manually 8 scan in barcode shown in book 9 update borrower and book files

19 © UCLES 2013 0420/12/O/N/13 [Turn over For Examiner's Use START customer selects book(s) END END No No Yes Yes Yes No Yes Yes No No barcode on borrower’s card scanned OUTPUT error message [6]

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/O/N/13 For Examiner's Use 16 (a) A greenhouse is being monitored by a computer using 2 sensors. SENSOR1 measures the temperature and SENSOR2 measures oxygen levels. If the temperature exceeds 45°C or oxygen levels fall below 0.19, then an error message is output by the computer. Write an algorithm, using pseudocode or flowchart only, which • inputs both sensor readings • checks the sensor input values and outputs a warning message if either are out of range • continues monitoring until the <ESCAPE> key is pressed (You may assume that READ SENSORn will take a reading from SENSORn and that READ KEY inputs a key press from the keyboard). [5] (b) Describe why a DAC (digital to analogue converter) would be needed if the computer is used to control the greenhouse environment. [2]

CAMBRIDGE INTERNATIONAL EXAMINATIONS International General Certificate of Secondary Education MARK SCHEME for the October/November 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 October/November 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 – October/November 2013 0420 12 © Cambridge International Examinations 2013 (1) (a) For each chosen security issue, 1 mark for description + 1 mark for method of protection. security issue description of security issue method of protection hacking gaining illegal/unauthorized access to a computer system – use of firewalls – use of passwords pharming code installed on the hard drive of a user’s computer or on actual web server; code redirects user to a bogus/fake website without user knowing – use of filters to authenticate websites – user should be alert and look for pharming clues which indicate being directed to a bogus site phishing creator sends legitimate-looking (fake) email in the hope of gaining personal/financial information; fake email replicates a well known company e.g. a bank – ISPs can filter/block out phishing emails – user should be wary of opening links in emails spyware software that gathers information by monitoring key presses on a user’s keyboard or activity and relays the information back to person who sent the spyware – use of dropdown boxes – user should be alert and look for clues when using their computer viruses Program or coding that replicates itself /corrupts the system/ alters or deletes data – anti-virus (software) – do not use disks/software from unknown sources – do not open emails from unknown senders [6]

Page 3 Mark Scheme Syllabus Paper IGCSE – October/November 2013 0420 12 © Cambridge International Examinations 2013 (2) (a) (i) – as first character(s) keyed in, rest of word predicted /word(s) suggested according to the letter(s) already entered [1] (ii) Any two from (items below are only examples): – MP3 player – Bluetooth – wifi – camera – Internet surfing – GPS [2] (b) 1 mark for each part: (i) – less expensive/cheaper than other telephone systems – can use webcams to have visual as well as text/speech (ii) – poor quality/drop out/echoes are very common problems – need to have fast broadband connection to work effectively (iii) – microphone and speaker/headphones – headset [3]

Page 4 Mark Scheme Syllabus Paper IGCSE – October/November 2013 0420 12 © Cambridge International Examinations 2013 (3) (a) 10/ten [1] (b) CB, CC, CG, CL < - 1 mark - > < - 1 mark - > (–1 mark for each additional item) [2] (c) (leather = “Y”) AND (silver = “Y” OR grey = “Y”) < - 1 mark - > < - - - - - - - - - - 1 mark - - - - - - - - - > or (silver = “Y” OR grey = “Y”) AND (leather = “Y”) < - - - - - - - 1 mark - - - - - - - > < - - - - 1 mark - - - - > or (leather = “Y”) AND ((silver = “Y”) OR (grey = “Y”)) < - 1 mark - > < - - - - - - - - - - 1 mark - - - - - - - - - > or ((silver = “Y”) OR (grey = “Y”)) AND (leather = “Y”) < - - - - - - - 1 mark - - - - - - - > < - - - - 1 mark - - - - > [2] (d) (green = “N”) [1] (e) Any one from: – uses up less memory (NOT space) – faster to key in data/saves time when keying in data – fewer mistakes made when keying in data [1]

Page 5 Mark Scheme Syllabus Paper IGCSE – October/November 2013 0420 12 © Cambridge International Examinations 2013 (4) (a) 1 mark for each application correctly linked to the appropriate hardware items. [3] (b) 1 mark for each additional item of hardware CAD – 3D (inkjet) printer – large monitor/screen – (graph) plotter – graphics tablet video conferencing – broadband modem – large monitor virtual reality – (data) helmet – simulator headset – sensor/data suit – haptic/motion sensor [3] speakers light pen microphone spaceball data goggles webcam data gloves computer aided design (CAD) video conferencing virtual reality

Page 6 Mark Scheme Syllabus Paper IGCSE – October/November 2013 0420 12 © Cambridge International Examinations 2013 (5) count total a b c d x y temp OUT- PUT 1 0 5 4 1 9 18 26 44 44 34 24 14 4 4 2 0 5 9 4 1 27 20 47 47 37 27 17 7 7 3 < - - - -1 mark - - - >< - - - - - - - - - - 1 mark - - - - - - - - - - ><1 mark><1 mark><1 mark><1 mark> [6]

Page 7 Mark Scheme Syllabus Paper IGCSE – October/November 2013 0420 12 © Cambridge International Examinations 2013 (6) (a) Any one from: – circular argument/reference – value in D2 not yet known – empty cell D2 [1] (b) = (A2 + C2 * B2) or = (A2 + B2 * C2) or = (A2 + C2 * 9.81) or = (A2 + 9.81 * C2) [1] (c) = (A7 + C7 * B7) or = (A7 + B7 * C7) or = (A7 + C7 * 9.81) or = (A7 + 9.81 * C7) [1] (d) = MAX(D2:D7) [1] (e) = (A2 + B2 * 9.81) or = (A2 + 9.81 * B2) [1]

Page 8 Mark Scheme Syllabus Paper IGCSE – October/November 2013 0420 12 © Cambridge International Examinations 2013 (7) (a) (i) 1 mark for causes: – repeated clicking of the mouse – prolonged use of a keyboard/typing 1 mark for way of removing problem: – take (regular) breaks – use wrist supports – use of ergonomic keyboards – use of voice recognition software – adjust chair to correct height [2] (ii) Any one from: – conduits/trunking for wiring – wires/cables attached to walls – wires under carpets/floors – use WiFi connections [1] (iii) One mark for risk: e.g. – glare from/staring for a long period of time at a computer screen – exposed wires – inadequate desk support – sitting too long in the same position – spilling liquids on computer equipment/inadequate ventilation One mark for corresponding description of risk (MUST match up) – can cause headaches/eye strain/dry eye – risk of electric shock/electrocution – equipment falling and causing injury – back/neck pain/injury/strain – fire risk [2] (b) Any two from: – need for training – possible redundancies/unemployment – work patterns may change (e.g. working from home/remote working) [2]

Page 9 Mark Scheme Syllabus Paper IGCSE – October/November 2013 0420 12 © Cambridge International Examinations 2013 (8) 1 mark for error + 1 mark for suggested correction to error (max of FOUR errors) description of possible error suggested correction to error line 20 lowest = 0 lowest = 100 (or even bigger value) line 30 loop count is 1 to 100 count should be 1 to 1000 e.g. for count = 1 to 1000 line 50 number = highest formula is reversed e.g. should be: highest = number line 60 number = lowest formula is reversed e.g. should be: lowest = number line 70 count = count + 1 addition of count in a for … to loop remove line 70 from coding [8] (9) Any three from: – viruses transmitted with attachment – possible phishing/spyware included with attachment – attachment file too large/not enough space in mailbox – she does not have the software to open the file – attachment corrupted during transmission – attachment was encrypted (and end user did not have encryption key) – password needed to open file/attachment (password not known) – virus checker/firewall detected virus and would not allow file/attachment to be opened [3]

Page 10 Mark Scheme Syllabus Paper IGCSE – October/November 2013 0420 12 © Cambridge International Examinations 2013 (10) (a) (i) A B X 0 0 1 0 1 1 1 0 1 1 1 0 [2] (ii) NAND gate (if truth table above is incorrect, allow follow through in part (ii)) [1] (b) A B C X 0 0 0 0 0 0 1 0 0 1 0 0 0 1 1 1 1 0 0 1 1 0 1 1 1 1 0 0 1 1 1 1 [4] } } 1 mark 1 mark } } } } 1 mark 1 mark 1 mark 1 mark

Page 11 Mark Scheme Syllabus Paper IGCSE – October/November 2013 0420 12 © Cambridge International Examinations 2013 (11) (a) 54 [1] (b) – multiplied by 2 – value 27 is doubled (to become 54) [1] (c) 108 [1] (d) (i) (ii) 184 [1] (iii) – no more places left in register/binary number – the left most 1 bit would disappear – number would become 112 (0111 0000) instead of 368 – number would be greater than 255 – overflow [1] (e) – divided by 2 – the number will be halved [1] 0 0 1 0 1 1 1 0 [1]

Page 12 Mark Scheme Syllabus Paper IGCSE – October/November 2013 0420 12 © Cambridge International Examinations 2013 (12) (a) Any one from: – trackerball/touch pad – touch screen [1] (b) Each validation check MUST be different for each input: goods reference number – length check – type/character check – presence check – check digit today’s date – format check – presence check – length check – range check (on each component) telephone number – type/character check – presence check – length check [3]

Page 13 Mark Scheme Syllabus Paper IGCSE – October/November 2013 0420 12 © Cambridge International Examinations 2013 (13) (a) download speed any one from: – speed at which information/data is transferred FROM server/Internet – speed at which information/data is transferred TO the user’s computer upload speed any one from: – speed at which information/data is transferred FROM user’s computer – speed at which information/data is transferred TO the Internet/server [2] (b) Any two from: – can use Internet connection and telephone at the same time – much faster data transfer speed – always “on” – charged for number of bytes/flat rate per month rather than actual time on line – more bandwidth [2] (c) Any two from: – when transferring large files/attachments with emails – when streaming music/video files/bit streaming – when using VoIP/video conferencing – software updates – online transactions – Using VLE (Virtual Learning Environment) [2] (d) 128 Mbits/sec = 16 Mbytes/sec Therefore, FOUR (4) files could be downloaded [1]

Page 14 Mark Scheme Syllabus Paper IGCSE – October/November 2013 0420 12 © Cambridge International Examinations 2013 (14) (a) Any two from: – lightweight – long battery life – cool running processor – touch pad – internal webcam [2] (b) Any one from: – security (prevent illegal copying of data) – storage of additional files/coding required to run software – software only licensed to specific computers – to allow the software to run on any computer [1] (c) Any two from: – multiple choice/yes-no answers – easy to understand interface e.g. use of icons/drop down menus etc. – output shown as % probabilities of fault [2] (d) Any three from: – knowledge base – rule(s) base – inference engine – explanation system – (expert system) shell [3]

Page 15 Mark Scheme Syllabus Paper IGCSE – October/November 2013 0420 12 © Cambridge International Examinations 2013 15 [6] No START customer selects book(s) barcode on borrower’s card 4 7 5 8 OUTPUT error message END 2 1 6 3 9 END No Yes Yes No Yes No Yes Yes No 1 mark 1 mark 1 mark 1 mark 1 mark 1 mark

Page 16 Mark Scheme Syllabus Paper IGCSE – October/November 2013 0420 12 © Cambridge International Examinations 2013 (16) (a) marking points: – correct loop 1 mark – reading of BOTH sensors 1 mark – check sensor1 + action taken 1 mark – check sensor2 + action taken 1 mark – read keyboard entry 1 mark sample coding: repeat read sensor1 read sensor2 1 mark if sensor1 > 45 then print “warning” 1 mark if sensor2 < 0.19 then print “warning” 1 mark read key 1 mark until key = ESCAPE 1 mark [5] (b) DAC Any two points from: – need to convert computer output to analogue values – to allow it to operate motors, actuators, …… – …… to open/close windows, switch heaters on/off etc. – devices may not understand/respond to digital signals [2]