Cambridge A Level Information Technology (from 2017) 9626 — 2017 Feb/March Paper 3 · Variant 2

1 A software application has been fully tested so that it is error-free and has been implemented. There are no new situations likely to arise but the management wants to ensure that the software is working as well as it should. Explain, with reasons, how you would maintain the software application. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... ......................................................................................................................................................[5]

Mark scheme: Question Answer Marks 1 Five from: 5 Because it is error-free, corrective maintenance is not needed Because there are no new situations likely to arise, adaptive maintenance is not needed Perfective maintenance is needed to modify the code ...enhance/add to the software capabilities to increase its usefulness Delete unused/obsolete functions to reduce the complexity/code size/resource requirements Optimise the code to increase functional speed

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2 Wearable, or body-borne, computers are miniature electronic devices worn by the bearer. Analyse the use of wearable computers by the police. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... ......................................................................................................................................................[8]

Mark scheme: 2 Eight from: 8 Benefits: (Body worn) video cameras used to record incidents for later use in court/enquiry Optical (head-mounted) technology to display information is in a similar format to a smartphone/act as a smartphone so is familiar Operated hands-free via voice activation Wrist-worn computers/smartphones for access to communications systems Wi-Fi-enabled/wireless connected clothing to track movements in real-time/connect peripherals ...monitor vital signs of officer ...maintaining constant communications with others Drawbacks: Reliance on computers can remove elements of human judgment Implementation can be expensive since this is an emerging technology Can lead to invasions of privacy for user and third parties... ...location and other details can be used to track the user Possibility of wearable computers being ‘hacked’ and data stolen/computers manipulated Breakdown in communications systems can lead to system failure Max 6 for all benefits or all drawbacks 1 mark available for a reasoned conclusion/opinion

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3 Fig. 1 shows a sequence of tasks that are required to complete a project. Task 2 Task 5 Start of Finish of Project Project Task 1 Task 3 Task 4 Fig. 1 The duration of each task is shown in this table: Task 1 2 3 4 5 Duration (days) 3 5 7 2 4 There are three paths through this set of tasks. (a) Use the information given in Fig. 1 and in the table to determine the critical path through the sequence of tasks. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ...............................................................................................................................................[6] (b) Each task can have an extra amount of time allowed over its stated duration before it causes the project to be delayed. This is the ‘float’. Explain how you would calculate the float for each of the tasks in the project. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ...............................................................................................................................................[4]

Mark scheme: 3(a) Six from: 6 1 mark for correct identification of critical path 2 marks for each correctly calculated path Path 3 is the critical path Path 1: start Task 1 Task 3 Task 4 finish = 3+7+2 = 12 Path 2: start Task 2 Task 5 finish = 5+4 = 9 Path 3: start Task 2 Task 5 Task 3 Task 4 = 5+4+7+2 = 16 3(b) Four from: 4 Each task on critical path has float of 0... ..tasks 2, 3, 4, and 5 Next longest path is path 1 with tasks 1, 3 and 4.... ..3 and 4 are on critical path so their float is still 0 ..so task 1 has float of critical path duration (16) minus Duration of path 1 (12) giving float of 4

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4 A website advertising a tourist resort uses both bitmap and vector graphics. Evaluate the suitability of these types of graphics for use on the website. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... ......................................................................................................................................................[8]

Mark scheme: 4 8 Answers/Indicative Level of Response content This question to be Level 3 (7–8 marks) marked as a Level of Response. Candidates will evaluate in detail the suitability of both Answers may make bitmap and vector graphics reference to e.g.: for use on the website. The information will be Photo-realism: bitmaps are relevant, clear, organised comprised of small pixels so and presented in a the bitmap is the most structured and coherent suitable format for photo- format. realistic images or images There will be a reasoned with high amounts of fine conclusion/opinion. detail. The vector image, on Subject specific terminology the other hand, does not will be used accurately and possess the same kinds of appropriately. photo-realistic capabilities because it is comprised of Level 2 (4–6 marks) larger objects and cannot achieve the kind of fine Candidates will explain the detail that is necessary for suitability of both bitmap and photo-realism. vector graphics for use on the website. Scalability: vector images For the most part, the are made of mathematically information will be relevant defined objects so sizes can and presented in a be easily manipulated with structured and coherent little to no loss in the quality format. of the image. The objects There may be a reasoned within a vector image are re- conclusion/opinion. rendered at a greater or Subject specific terminology smaller scale to provide will be used appropriately consistently smooth edges. and for the most part Bitmaps are more difficult to correctly. scale because changing the size of a bitmap requires a Level 1 (1–3 marks) complete rearrangement of Candidates will describe the the pixels. An enlarged suitability of bitmap and/or bitmap is likely to appear vector graphics for use on blurry, or “pixelated,” the website. meaning that the different Answers may be in the form pixels of the image have of a list. become visible. There will be little or no use of specialist terms. Shape: a bitmap image always has four straight Zero marks: Response with edges while vector images no valid content can be any shape. Answers/Indicative Level of Response content File size: complex vector images can have a very large file size due to the complex instructions needed to create them; the size of the file is not dependant on the size of the image: small complex images can have a large file size; bitmap images can be large but can be compressed. Conversion between file types: the most common file type for bitmap web images are jpeg or gif, and conversion to these is simple without loss of quality; conversion of vector images often results in more loss of quality.

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5 Global positioning systems (GPS) are used by navigation devices to allow drivers of cars to find locations and destinations. (a) Describe how GPS signals from satellites are used by navigation devices to determine a location. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 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................................................................................................................................................... ...............................................................................................................................................[8] (b) Describe the factors that could degrade a GPS signal, when it is transmitted to a navigation device, and affect the accuracy of the location found by that device. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 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Mark scheme: 5(a) Eight from: 8 (Civilian) signals from satellite travel by line of sight to navigation device/ receiver Use L1/1575.42 MHz in UHF band Satellites are Low Earth Orbit/LEO Signal contains ID code of the satellite ...and status/health information ...and current date and time from atomic clock in the satellite ...and almanac data about where each GPS satellite is at any point in time Navigation device/ receiver must lock to (at least) 2 satellites to calculate 2D position (i.e. latitude and longitude) To 4 or more (usually 4 to 7) satellites to calculate 3D position (i.e. latitude, longitude and altitude/elevation) Using trilateration techniques Calculation by finding intersect point by timing the signals from the satellites 5(b) Five from: 5 Atmospheric/ionosphere/ troposphere delays slowing the satellite signal slows as it passes through the atmosphere Signal multipath errors as the GPS signal is reflected off objects before it reaches the receiver ...increases the travel time of the signal Clock errors in the receiver because the built-in clock is not as accurate as the atomic clocks on board the GPS satellites Orbital errors ( ephemeris errors) of the satellite's reported location The number of satellites visible may be too few because buildings/terrain/dense foliage may block the signal reception electronic interference can block the signals ...causing position errors /no position reading ...GPS units usually will not work indoors, underwater or underground Satellite geometry/shading because the relative position of the satellites at any given time is not ideal for signal reception by the receiver ...the satellites should be located at wide angles relative to each other ...poor geometry occurs when the satellites are located in a line/tight grouping Intentional degradation of the satellite signal by the operator/owner of the satellites ...to prevent military adversaries from using the highly accurate GPS signals

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6 A customer in a restaurant can pay the bill with a credit card using a mobile chip and pin reader carried by a waiter. Describe the computer processing involved in the payment of the bill by credit card using the mobile chip and pin reader. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... ......................................................................................................................................................[8]

Mark scheme: 6 Eight from: 8 Reader communicates via secure wireless connection with restaurant base-station Base station communicates with bank computers Mobile reader reads the data from the card Requests input of PIN from customer PIN checked/validated against stored PIN Request sent to restaurant’s bank to determine the cardholder’s bank/issuing bank Request sent to card issuer/bank to authorise the transaction ...authorisation code sent to restaurant’s bank if credit is available Credit card is validated/credit available ...if valid/available then transaction can proceed ...if not valid/available then transaction is refused If transaction can proceed the amount of the transaction is deducted from the cardholder’s account Receipt is printed from the mobile reader

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7 Electronic data exchange is often called electronic data interchange. An online retailer and its trading partners use electronic data interchange (EDI). (a) Define EDI. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ...............................................................................................................................................[3] (b) The retailer has prepared an order that has to go to a supplier. When the supplier has received the order, an invoice asking for payment for the goods has to go back to the retailer. Explain how you would use EDI for these transactions. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ...............................................................................................................................................[5]

Mark scheme: 7(a) Three from: 3 The computer-to-computer Exchange of business documents Using a standard electronic format Between business partners 7(b) Five from: 5 Prepare the documents to be sent Collect/organise the data via human interface screens/typing Extract from databases/spreadsheets/output from stock control/purchasing systems into data files Translate the documents into EDI format Convert internal data into EDI standard format Transmit the EDI documents to trading partner Use VPN/secure private network Via an EDI network provider that connects the trading partners together

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8 Packet switching is used to transfer data around networks. Discuss the benefits and drawbacks of packet switching. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... ......................................................................................................................................................[8]

Mark scheme: 8 Eight from e.g.: 8 Benefits of Packet Switching include e.g.: Makes very efficient use of the network as communication lines are shared Data packets can be routed around unusable nodes/parts of the network so if part of network/node is faulty/not working packets can still reach destination The network only has to expand slowly with increase in users compared to circuit switching Drawbacks of Packet Switching: The packaging of the data changes each time a packet is switched so there is a time overhead/latency Can cause a problem for time-critical information such as an emergency signal/video streaming Small data packages are inefficiently packaged (e.g. a data package of 600 bytes uses two packets of 512 bytes plus the address information) Max 6 for all benefits and drawbacks 1 mark available for a reasoned conclusion/opinion

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9 JavaScript can be embedded in the code of web pages to add interactivity to a page. Jonas uses JavaScript code to store, list and display the names of cities on a web page. (a) Two methods of storing the names are shown below. Method 1: var city1 = "London"; var city2 = "Cambridge"; var city3 = "Oxford"; var city4 = "Manchester"; Method 2: var city = ["London", "Cambridge", "Oxford", "Manchester"]; Explain why storing the names using Method 2 is more suitable for storing large numbers of cities. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ...............................................................................................................................................[4] (b) Jonas has added some lines to the JavaScript code: /* The code below stores the list of cities. */ var city = ["London", "Cambridge", "Oxford", "Manchester"]; Explain why Jonas would have added the new code to the script. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ...............................................................................................................................................[2] (c) Jonas wants to extract ‘Oxford’ from the list in the code below to display it on the web page. var city = ["London", "Cambridge", "Oxford", "Manchester"]; Write a line of JavaScript code to access the list and store the city name. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ...............................................................................................................................................[3] (d) Write a loop in JavaScript code to extract and display the first three city names. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ...............................................................................................................................................[4]

Mark scheme: 9(a) Four from: 4 Method 2 uses an array... ....which stores multiple values in a single variable More suitable for storing large numbers of items/data items as it reduces the complexity of the code Increases the code easier to understand Increases the execution speed of the code Method 2 can be looped through using an iterative function ...to find a specific data item 9(b) Two from: 2 Jonas wanted to explain/add comments to the code/what the line of code means/is for To make it clear that the code referred to a list of the cities Ensures that the explanation/comment was ignored by the web browser To make the code more readable/understandable 9(c) A suitable line of code would be: var place = city(2) 3 Three from: var =1 mark plus suitable variable name to store city e.g. place =1 mark = city(2) =1 mark 9(d) Suitable code would be: 4 for (b = 0; b <= 3; b++) { document.write (city (b)); } Marks, four from: for () 1 mark suitable var names 1 mark count from to 0 to 2 (b from 0 to <=3) 1 mark adding 1 inside loop (b++) 1 mark displaying the result of loop 1 mark

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10 A new computer system is to be developed for a factory. You have been asked to gather information from the managers, assembly-line workers and clerical staff about the current system. The managers can be available at any time, the assembly-line workers must not be interrupted at any time and do not like taking work home, and the clerical staff are very busy during their working hours and do not like being watched. Describe, with reasons, the method of research you would use to gather information from each group. (i) Managers: ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ...............................................................................................................................................[3] (ii) Assembly-line workers: ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ...............................................................................................................................................[3] (iii) Clerical staff: ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ...................................................................................................................................................

Mark scheme: 10(i) Three from: 3 Interview face-to-face with managers asking about their views/opinions of the current system Managers can be available for in depth discussion/additional questions Not many managers, so time is not a constraint/consideration 10(ii) Three from: 3 Observation of the assembly workers to avoid disturbing/ distracting them at/from their work Observers can see the process first hand/for themselves Observers do not need to understand the technical language of the process 10(iii) Three from: 3 Using questionnaires so that clerical staff can take them away and complete in own time Questionnaires can be anonymously returned/completed Cannot use observation as the clerical staff behaviour could change Too many clerical staff to interview Clerical staff can remain anonymous Total: 90

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