Cambridge IGCSE Computer Studies 0420 — 2010 Oct/Nov Paper 1 · Variant 3

This document consists of 19 printed pages and 1 blank page. IB10 11_0420_13/6RP © UCLES 2010 [Turn over *8051666953* For Examiner's Use UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS International General Certificate of Secondary Education COMPUTER STUDIES 0420/13 Paper 1 October/November 2010 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 2010 0420/13/O/N/10 For Examiner's Use 1 Explain, with examples where appropriate, the following five computer terms. (a) interrupt [2] (b) optical media [2] (c) CAD [2] (d) verification [2] (e) global positioning system (GPS) [2]

3 © UCLES 2010 0420/13/O/N/10 [Turn over For Examiner's Use 2 (a) What is meant by the term drop-down menu? [1] (b) Give an example of where a drop-down menu could be used. [1] (c) Give one disadvantage of a drop-down menu. [1] 3 A typical computer system contains the following four components:
RAM
ROM
hard disk
modem Describe the function of each of these components. RAM ROM hard disk modem [4]

4 © UCLES 2010 0420/13/O/N/10 For Examiner's Use 4 (a) Describe two differences between batch processing and real-time transaction processing. 1 2 [2] (b) Give one example of the use of each type of processing. batch: real-time transaction: [2]

5 © UCLES 2010 0420/13/O/N/10 [Turn over For Examiner's Use 5 Most laptop computers have networking capability. (a) Describe two other desirable features you would look for when choosing a laptop computer. 1 2 [2] (b) Describe two advantages of using broadband to connect to the Internet rather than using dial-up. [4]

6 © UCLES 2010 0420/13/O/N/10 For Examiner's Use 6 Complete the following table by writing down the most appropriate data collection method for the given application. Application Data collection method Reading information from a credit/debit card Choosing an option from a customer information screen at an airport Reading the results from a questionnaire where pencil lines were used to choose options [3] 7 Name two of the common methods used to change over to a new computer system. For each named method, give one advantage and one disadvantage. Method 1 Advantage Disadvantage Method 2 Advantage Disadvantage [6]

7 © UCLES 2010 0420/13/O/N/10 [Turn over For Examiner's Use 8 Describe how computers are used to generate graphics and animation effects for use in films and arcade games. [3]

8 © UCLES 2010 0420/13/O/N/10 For Examiner's Use 9 Students at a school decide to produce a monthly newsletter to inform parents of events. They could either produce a magazine on paper or arrange for a multimedia presentation in the school hall. (a) State two advantages and two disadvantages of producing the magazine on paper. Advantage 1 Advantage 2 Disadvantage 1 Disadvantage 2 [4] (b) State two advantages and two disadvantages of giving a multimedia presentation. Advantage 1 Advantage 2 Disadvantage 1 Disadvantage 2 [4]

9 © UCLES 2010 0420/13/O/N/10 [Turn over For Examiner's Use 10 (a) What is meant by a virus? [2] (b) What is meant by encryption? [2] (c) (i) A student wrote “I would make backup copies of my data to guard against viruses”. Why is the student’s statement not necessarily true? [1] (ii) The same student also wrote “Encryption would stop a hacker accessing the data in my computer files”. Why is the student’s statement incorrect? [1]

10 © UCLES 2010 0420/13/O/N/10 For Examiner's Use 11 (a) Which validation methods are being carried out by the following three pseudocode statements? (i) if age > 10 and age < 20 then print "correct" (ii) if gender = "male" and title = "Mr" then print "correct" (iii) if field = "" then print "input data is missing" [3] (b) Name a different validation technique and give an example to show how it works. Name Example [2]

11 © UCLES 2010 0420/13/O/N/10 [Turn over For Examiner's Use 12 (a) A student is trying to find out information about cloud computers. How could he use the Internet to find this information? [2] (b) Give two advantages of using the Internet to find information. 1 2 [2] (c) Give two disadvantages of using the Internet to find information. 1 2 [2]

12 © UCLES 2010 0420/13/O/N/10 For Examiner's Use 13 A spreadsheet has been set up to compare the monthly costs of five mobile phone networks. Normally a text message costs 2 cents and one minute of talk time costs 15 cents for all networks (100 cents = $1). A B C D E 1 Network name Monthly charge ($) No. of free texts No. of free talk time minutes Value of texts + talk time ($) 2 Lemon 65 500 500 85 3 Yodafone 65 1000 280 62 4 C-mobile 65 800 400 76 5 O-3 65 1000 500 95 6 T-world 65 2000 100 55 7 Best network: (a) What formula must be in E2 to calculate the value of the Lemon network offer? [2] (b) What formula needs to be placed in E7 to find the best offer? [1] (c) The customer actually uses 800 minutes of talk time per month. How could the spreadsheet be modified so that the customer can find out which network still gives him the best deal? [2]

13 © UCLES 2010 0420/13/O/N/10 [Turn over For Examiner's Use 14 An airport has a number of hotels nearby. A database has been set up to give customers information to allow them to select a hotel. Hotel Ref Name of hotel No. of stars No. of rooms Hotel parking Price per person ($) Distance from airport (km) H41 The Grand 3 45 Y 65 11 K22 Sleepy Inn 2 15 N 45 10 N15 Britannia 5 140 Y 150 4 L44 Beach Hotel 4 62 N 85 8 H30 Sea View 3 38 N 60 4 H21 Pyramid 3 25 N 70 5 N21 Superior 5 120 Y 200 2 K14 Travellers 2 15 N 45 10 (a) How many records are shown in the database? [1] (b) Which field in each record must be unique? [1] (c) The following search condition was typed in: (No. of stars > 3) OR (Hotel parking = Y) Using Hotel Ref only, which records would be found? [2] (d) Write down the search condition to find which hotels were less than 10 km from the airport and charged under $100 per person. [2] (e) The database was sorted into descending order using No. of rooms. Using Hotel Ref only, write down the sorted order of records. [2]

14 © UCLES 2010 0420/13/O/N/10 For Examiner's Use 15 (a) The following flowchart shows how a burglar alarm system uses light sensors to determine if an intruder has entered the house and decides to sound an alarm. Select statements from the list below, using numbers only, to complete the flowchart. START Light sensor detects movement No No Yes Yes No Yes Yes No 1 check sensor value with the stored value 2 convert signal to digital 3 has alarm been re-set? 4 is a signal detected? 5 is sensor value nominal? 6 is signal digital? 7 sound an alarm List of statements [4]

15 © UCLES 2010 0420/13/O/N/10 [Turn over For Examiner's Use (b) Explain why the sensor signal needs to be converted into digital. [2] (c) Name a different sensor and describe an application that uses the named sensor. Sensor name: Description: [2] (d) The computer can’t directly control items such as motors and heaters. What additional hardware is needed to allow the computer to control these devices? [1]

16 © UCLES 2010 0420/13/O/N/10 For Examiner's Use 16 A customer logs on to a secure website using a code and a password. The first stage is to key in a code which is his date of birth (DDMMYY) followed by 1234. The second stage is to type in the first, third, fourth and seventh character of his password. The customer last logged on to the website on 15th March 2010. (a) (i) The customer’s date of birth is 15th November 1985. What is the customer’s code? (ii) Why is this code not unique? (iii) Suggest how this coding system could be improved. [3] (b) (i) The customer’s password is PAULO168. What does the customer need to type at the second stage? 1st 3rd 4th 7th (ii) Why are passwords used? [2]

17 © UCLES 2010 0420/13/O/N/10 [Turn over For Examiner's Use (c) If the customer gets through the two stages above he is then directed to a new security page which states: “You were last logged on to this website on 14th April 2010. Is this correct?” What could have happened to make the customer concerned about this statement? [1]

18 © UCLES 2010 0420/13/O/N/10 For Examiner's Use 17 (a) Write an algorithm, using pseudocode or a flowchart, which
inputs a set of positive numbers (which end with -1)
outputs the average (mean) value of the input numbers
outputs the value of the largest (highest) number input [4]

19 © UCLES 2010 0420/13/O/N/10 For Examiner's Use (b) Write an algorithm, using pseudocode or a flowchart, which
inputs a whole number (which is > 0)
calculates the number of digits in the number
outputs the number of digits and the original number (E.g. 147 would give an output of 3, 147) [4]

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. 0420/13/O/N/10 BLANK PAGE

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS International General Certificate of Secondary Education MARK SCHEME for the October/November 2010 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. • CIE will not enter into discussions or correspondence in connection with these mark schemes. CIE is publishing the mark schemes for the October/November 2010 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 2010 0420 13 © UCLES 2010 1 (a) Interrupt Any two points from: – a signal/request generated by a device/program – which causes a break in the execution of the program/stops the program – examples: printer out of paper, <BREAK> key pressed, disk full [2] (b) Optical media Any two points from: – type of non-magnetic memory – uses light sensitive surface to store data – media are very portable – can be write once or write many times – used to store large files – can be ROM or RAM – examples: CD, DVD [2] (c) CAD Any two points from: – computer aided design – uses special hardware such as hi-res screen, plotters, spaceball – makes use of features such as 2D, 3D, wire frames, costings, zoom – use a library of spare parts – often used with CAM – examples: architecture designing buildings, car design, lighting at concerts [2] (d) verification Any two points from: – check on input for errors – check before and after transfer (of signals) – by double entry – on screen checking – comparing input/use of second operator – e.g. typing in a password twice [2] (e) GPS Any two points from: – Global positioning system – navigational system – uses satellites – which transmit data … – … to determine exact location and time – satellites use atomic/very accurate clocks – sat nav computer calculates position based on satellite data – examples: used in vehicles to find routes from a to B [2]

Page 3 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – October/November 2010 0420 13 © UCLES 2010 2 (a) Any one point from: – choose options by clicking on an arrow – which highlights possible options – uses a pointing device (e.g. mouse) to select – list of items to select/click on – an inactive drop-down menu only has one value [1] (b) Any one point from: – when selecting an option from a finite list – e.g. choosing an expiry date for a credit card – navigating between web pages [1] (c) Any one point from: – limited options available – difficult to find the required option, as only one option is visible [1] 3 RAM – allows random access – stores work user is currently working on – stores files/data temporarily when s/ware running ROM – stores BIOS – stores files/data that should not be changed Internal hard drive – main memory of the computer – stores applications software Internal modem – allows computer to link to a network/internet – allows modulation/demodulation to enable info to be sent/received by analogue cables – controls the flow of data – error correction – compresses data transmitted – converts digital to analogue and vice versa [4] 4 (a) Any two points from: Real time transaction: – individual transactions processed as it occurs – fields/files updated immediately Batch processing: – all data collected together before processing started – processed in one go – processing often done at night during “quiet periods” – no need to up date files immediately [2] (b) Any one use of batch: – processing of utility bills (gas, electricity, water, …) – processing of cheques – payroll – producing wages/salary slips Any one use of RTT: – on line booking of seats in a cinema, flights, … – any application where double booking must be avoided [2]

Page 4 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – October/November 2010 0420 13 © UCLES 2010 5 (a) Any two points from: – consume very little power … – … hence prolonging internal battery life – run cool … – … thus minimising problem of heat dissipation – no processor fans needed … – … therefore prolonging internal battery life – light weight for easier portability [2] (b) Any two advantages from: (1 mark for advantage + 1 mark for expansion) – very fast transfer/conncetion rate … – … thus can download/upload files much faster – always “on” (no need to dial up) … – … thus don’t have to wait/have instant access to the Internet – not metered … – … thus it is possible to download large files without additional cost – telephone lines not tied up whilst computer in use … – … this is because broadband uses a wide bandwidth – because of the high data transfer rate … – … it is possible to do video conferencing or use VOIP systems [4] 6 One mark for each method: Data collection method magnetic stripe reader OR chip and PIN reader touch screen OMR [3] 7 1 mark for named method, 1 mark for advantage and 1 mark for each disadvantage (these MUST match up with named method) Direct: Advantages: – less likely to malfunction since fully tested – immediate benefits/less time wasted – reduced costs (only one system so no need to duplicate staff) Disadvantages: – disastrous if the new systems does fail Parallel: Advantages: – if new system goes down, there is a backup system in place – possible to gradually train staff/staff have time to get used to the new system

Page 5 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – October/November 2010 0420 13 © UCLES 2010 Phased: Advantages: – only a small part of the operation affected if new system fails – no need to pay for two sets of wages Disadvantages: – time consuming (each part needs testing fully before expanding system) Pilot: Advantages: – if new system fails, only that part will be affected – possible to gradually train staff on pilot before whole system changes over Disadvantages: – time consuming (waiting to see how pilot works before rolling out to rest of the organisation) [6] 8 Any three points from: – animation effects produced by animator using key frames (which define start point and end point of a movement e.g. open the mouth) – use of tweening/morphing (differences in appearance between key frames are calculated using tweening/morphing) – use of avars (animation variables) – successive sets of avars control movement of animated character – adding of surfaces to avars using rendering (realistic image) – generation of avars using markers on real moving objects … – … or using joystick to manually produce stick models – software prevents need to produce hundreds of hand drawn sketches [3] 9 (a) 1 mark for each advantage and 1 mark for each disadvantage: Advantages: – reaches a larger audience – people can read information on paper copies at their leisure – permanent copy which can be referred back to later Disadvantages: – need a high quality colour printer – cost of ink, paper, etc. – no sound, video, animation or special effects – need to distribute by hand (time and cost issues) [4] (b) 1 mark for each advantage and 1 mark for each disadvantage: Advantages: – can be interactive with the presenter – can have sound, video, animation or special effects – easier to update (don’t have to re-print or re-distribute) Disadvantages: – not a permanent record – people may not go to the presentation – need expensive equipment (e.g. projector) – needs to be set up each time it is used [4]

Page 6 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – October/November 2010 0420 13 © UCLES 2010 10 (a) Any two points from: – a program/software/code – which can replicate itself automatically – attach themselves to e.g. files – cause damage to computer system (e.g. delete/change/corrupt data) [2] (b) Any two points from: – data which is jumbled up … – … to prevent unauthorised people from understanding data – a key is needed to encrypt data (encryption key) – a key must be known to decrypt data (decryption key) – even if data is accessed it can’t be read without necessary key [2] (c) (i) Any one point from: – viruses could be attached to the data and backup copies may still be “infected” – when copying backup data onto computer may transfer virus again [1] (ii) Any one point from: – encryption only makes data, already accessed, unreadable – encryption doesn’t stop access to files [1] 11 (a) (i) range check (ii) consistency check / crossfield check (iii) presence check [3] (b) 1 mark for name and 1 mark for example. Example must match name Name Example – type/character check only letters typed into name field – format check ensure date typed in correct format – length check ensure year field has four digits – check digit on barcodes to ensure they have been read correctly [2] 12 (a) Any two points from: – use a search engine … – … and enter KEY words (e.g. CLOUD + COMPUTER) [2] (b) Any two advantages from: – more likely to be up-to-date – can contain multimedia files – more information is available – can find information anywhere (e.g. away from home) – usually faster than looking through paper-based information (must be a comparison) – easier to incorporate information into own work, projects, etc. [2]

Page 7 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – October/November 2010 0420 13 © UCLES 2010 (c) Any two disadvantages from: – not regulated/checked, therefore may be inaccurate/incorrect – easy to get irrelevant information/sites/overabundance of info – can download viruses, spyware, etc. – risk of finding porn sites – need to invest in computer system + broadband – sometimes information is withdrawn and is lost from the Internet [2] 13 (a) = (C2 * 0.02) + (D2 * 0.15) ← 1 mark → ← 1 mark → [2] (b) = MAX (E2:E6) [1] (c) Any two points from: – new column F added – new formula e.g. F2 = 65 + (800 – D2) * 0.15 – modify formula in, e.g. E2, to include (800 – D2) * 0.15 [2] 14 (a) 8 [1] (b) Hotel Ref [1] (c) H41, N15, L44, N21 (-1 for each error or omission) [2] (d) (Distance from airport (km) < 10) AND (Price per person($) < 100) ←-------------- 1 mark ---------------→ ←------------- 1 mark --------------→ OR (Price per person($) < 100) AND (Distance from airport (km) < 10) ←---------- 1 mark ----------→ ←------------------ 1 mark ------------------→ [2] (e) N15, N21, L44, H41, H30, H21, K22, K14 ↑ (last 2 in any order) [2]

Page 8 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – October/November 2010 0420 13 © UCLES 2010 15 Award marks as shown below 1 = check sensor value with stored value 2 = convert signal to digital 3 = has alarm been re-set 4 = is a signal detected? 5 = is sensor value normal? 6 = is signal digital? 7 = sound an alarm [4] (b) Any two points from: – sensor information/signal usually analogue – computers can only read/understand digital signals [2] 2 1 5 7 3 6 No Yes Yes No Yes No Yes No START Light sensor detects movement 4 (1 mark) (1 mark) (1 mark) (1 mark)

Page 9 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – October/November 2010 0420 13 © UCLES 2010 (c) 1 mark for name of sensor + 1 mark for application Application must match the sensor Can have the same application for different sensors Sensor type Possible applications temperature (1) (2) used in controlling central heating systems used to control/monitor temperatures in chemical processes moisture (1) (2) monitoring of greenhouse environment any process where moisture is an issue (e.g. production of tablets in a pharmaceutical company) oxygen (1) environment (e.g. measuring oxygen content in a river to check for pollution) infra red (1) (2) detecting an intruder by breaking an infra-red beam counting (e.g. counting coins as each one breaks the beam) pressure (1) (2) detecting intruders in a burglar alarm system some systems still use these to count vehicles on the road acoustic (1) (2) picks up sound (e.g. burglar alarm system) detecting liquids moving in pipes (chemical processes) motion (1) detecting speed (e.g. radar guns measuring vehicle speed) pH (1) (2) (3) used to measure acidity in rivers (pollution monitoring) used in greenhouses to monitor soil acidity used to monitor/control chemical process where acidity levels are important proximity/distance (1) these tend to be versions of the above (e.g. light or infra-red) [2] (d) Any one from: – DAC (digital to analogue converter) – actuators [1] 16 (a) (i) 1 5 1 1 8 5 1 2 3 4 [1] (ii) more than one person can have same date of birth [1] (iii) Any one from: – give different 4-digit codes to people – increase the number of digits in code (e.g. 10 instead of 4) [1]

Page 10 Mark Scheme: Teachers’ version Syllabus Paper IGCSE – October/November 2010 0420 13 © UCLES 2010 (b) (i) 1st 3rd 4th 7th [1] (ii) to prevent illegal access to the website [1] (c) Any two from: – he last logged on on 16th March 2010 and system shows 14th April 2010 – there is evidence of illegal access [1] 17 (a) highest = –100; total = 0: count = 0 (1 mark) initialise values NB highest cannot be 0 input number (1 mark) inputs in the correct place while number < > –1 do (1 mark) loop until –1 is input total = total + number (1 mark) calculate number total count = count + 1 and count numbers input if number > highest then highest = number (1 mark) highest input number endwhile average = total/count (1 mark) calculate average value print average, highest and output average and highest value [4] (b) d = 0 (1 mark) initialise value input number (1 mark) input number and set variable t = number to this number repeat (1 mark) correct loop t = t /10 (1 mark) **method to find number of digits d = d + 1 (1 mark) **counting number of digits until t < 1 print number, d (1 mark) correct output outside the loop (** NOTE: there are other ways of finding number of digits e.g. if number > 0 then d = 1 else if number > 9 then d = 2 … … … … … … … … … … … else if number > 999999 then d = 7 etc.) If no loop then 0 for loop and 0 for output [4] P U L 6