Last changed: March 9, 2022 11:35 AM
VCE Applied Computing Notes by Mark Kelly
Software DevelopmentVCAA Exam Post Mortem2015 |
Post Mortem Notes This is not a VCAA publication.
I do not speak for the VCAA, the IT examiners, or exam markers. I was not involved in the writing or marking of this examination. Extracts from exams are all Copyright © VCAA, and are used with permission. Use these post mortems at your own risk. I reserve the right to change my mind completely, at short notice, about anything I've said here. Suggestions, discussions and corrections are welcome. Questions look like this. |
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The exciting Illiteracy Award for crimes against the English language. |
Written examinationFriday 13 November 2015 Reading time: 3.00 pm to 3:15 (15 minutes) Writing time: 3:15 to 5:15 pm (2 hours)
Materials supplied
Instructions
At the end of the examination
Students are NOT permitted to bring mobile phones and/or any other unauthorised electronic devices into the examination room. |
SECTION B - short answer questionsInstructions for Section B [x lines] indicates the number of ruled lines provided on the paper for the answers. |
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Question 1 Annalie asks a programmer, Sam, to help her code a program. She suggests that 50 per cent of code lines be internal documentation as that is her company's normal practice. Sam says that adding internal documentation is a waste of time and he can work much faster if he just leaves out all internal documentation. a. Outline two reasons to support Annalie's suggestion of adding internal documentation. 2 marks Reason 1 [4 lines] It makes the meaning and purpose of the code clear to programmers. Code tends to be terse and its operation unclear. Adding remarks explains what the code is meant to do. Using code indentation and good object naming (other forms of internal documentation) makes code more readable and self-explanatory. Reason 2 [4 lines] It makes the code easier to maintain in future. Trying to understand someone else's code (or even your own code) after time has elapsed can take a lot of study without the explanations offered by internal documentation. Most students were able to provide two reasons to support the addition of internal documentation, b. Describe one naming convention that you have used in programming. Explain how this convention makes programming better. Give an example to support your answer. 3 marks [6 lines] Hungarian Notation - the use of a prefix to identify the type of object, such as intLength for an integer or lblName for a label. The prefix ensures each object is treated appropriately, and you don't try to store decimal places in an integer, or forget that 'Name' is a label rather that a textbox and try to set properties that don't exist for that class of object. or CamelCase - since one can't use spaces in object names, using capital letters for the initial letter of each words in an object's name makes it easier to identify the different words in the name. e.g. 'TimeOfArrival' is easier to read than 'timeofarrival'. Although students had an understanding of naming conventions many did not fully answer the
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Question 2 A pathology company provides patients with a device to monitor their blood sugar levels on a daily basis. After taking a reading, patients enter their blood sugar level readings into a website.
A use case diagram is drawn to help understand the system.
A pretty basic and repetitive UCD task, IMO. Yes. Thanks to Brody for the prompt! Then a third possibility comes to mind too. Since the pathologist will firstly analyse (requiring the login) and then store, the 'store results' use case could be shown as an includes as well. Fourth possibility is that the 'store results' use case is an <<extends>> if the pathologist did not always store the results of the analysis. But in either case, the association line from pathologist to the 'store results' use case would need to be removed, and it's all getting rather too complex, and the assigned number of marks doesn't make sense again.
Most students struggled to indicate the four required relationships. A common error was showing Above is the examiner's solution. |
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Question 3 Sue has written a program to record the results of History tests. She has decided to use a two-dimensional array to hold the results of four tests so that each row corresponds to a student. The programming language that she is using does not allow her to mix data types. She has decided to set up a one-dimensional array sorted by students' names, Names[ ], to store the students' names. Each position in Names[ ] corresponds to the position of the student's results in the two-dimensional array, called Results[ ][ ]. In this case, the index values start with 1.
a. The total mark for each test is 30. No half-marks are awarded. 28. You mean - that's IT?
That's all? Just effectively read a table? And why was it necessary to point out "The total mark for each test is 30. No half-marks are awarded." The correct response was 28. AVERAGE MARK 1. b. The lowest test score is 14. Results[2,3] Many students were able to read the array correctly and provide the index values for i and j in c. To find the total of the four test scores of a student, would Sue write a procedure to find the sum of each column or the sum of each row? 1 mark [1 line] Each row. Most students were able to identify that the sum of each row was required to perform the d. State two reasons why Sue has used a two-dimensional array instead of four one-dimensional arrays to store the test scores. 2 marks [4 lines] 1. Using 4 arrays, she would have had to repeat code four times to manipulate each test. This is a lot of unnecessary coding that would only make the software bigger and slower - and no better. 2. Using one array means she can quickly and easily use nested loops to process all students and all tests in one operation. She could loop vertically to add all students' test results and then generate a class average for each test, or horizontally add values to get each student's total or average over all four tests. This would have been a chance to get students to write pseudocode to actually create a test average for each student. A number of possible reasons were accepted; however, more commonly students identified that it
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B4 (2 marks) |
Question 4 Teachers and students use the same computer network in a school. Teachers are concerned that tests and personal information kept on their computers may be accessed by students. A penetration test (pen test) could be organised whereby someone (perhaps a reliable and skilful student) attempts to access some dummy information that has been placed in a teacher's data storage area on the network. If the person can access the dummy information without being given any special privileges or credentials, the network has been shown to be insecure and should be strengthened. Students were asked to describe a test that could be carried out to see if students were able to
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Question 5 Explain how error logs can be used to measure the reliability and maintainability of a network. Reliability [5 lines] The more errors that are recorded in the log over time, the greater the evidence that the system suffers from faults and is not reliable. If there are few errors in the log, the system is more reliable. Maintainability [5 lines] If the error rate reported in the log increases over time, it's a sign that the system is hard to maintain and is becoming increasingly error-prone. If the error rate stays consistent, it is evidence that the system can be repaired and upgraded appropriately because it's not getting any worse. Students answered this question with varying degrees of success. It was important for students to
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Section B overall -
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Case studyCASE STUDY INSERT FOR SECTION C Case study Case study The current proposal is to use specially designed desktop computers (voting machines) connected to a server at each polling booth. Each of the servers will be linked to the main server at the council's office. When voters cast their votes, the data will be uploaded to the local file server at the polling booth. A file of voters who have voted will be created and a separate file containing the actual votes, stripped of any identification, will also be created. These files will then be transmitted to the local council records, where they will be stored on the main server as part of the council's computer system. All voters who cannot attend on Election Day will be required to vote earlier at the council's office or request access to the mobile voting service, if they meet certain eligibility criteria. The mobile voting service will be available to voters who live within the council's boundaries and are at least 80 years of age or have a diagnosed medical condition that may prevent them from travelling to a polling booth. A mobile device will be brought to eligible voters so that they can cast their vote. The mobile device will be connected wirelessly to the main server at the council's office. The proposed voting system will operate two weeks prior to, and on, Election Day. Voters who need to vote before Election Day will be required to come into the council's office during this period to cast their votes. The mobile service will be available only on application.
END OF CASE STUDY INSERT FOR SECTION C |
Instructions for Section C Answer all questions in the spaces provided. Remove the case study insert and read all the information provided before you answer these questions. Answers must apply to the case study. |
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(2 marks)
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Question 1 The council has appointed the company Marvellous Management Systems (MMS) to produce the voting software. The council has provided the information in the case study insert and has asked MMS for the software requirements specifications (SRS) document as soon as possible. An SRS documents the scope, constraints and requirements of the new software, and is used to guide the design, development and evaluation of the system. The study design indicates that the ‘software requirements specifications fulfils the purposes of
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(4 marks) |
Question 2 Sally, as the manager of the voting software for MMS, is beginning to write the SRS document. Requirement 1 [1 line] - It must be able to work on a mobile device. Explanation [2 lines] - Voters who can't attend on Election Day will be visited at their home so they can cast their vote. This will only work if the software can be run on a mobile device. Requirement 2 [1 line] - It must work quickly. Explanation [3 lines] - One expected advantage is that it allows for election results to be known earlier. Also:
A number of non-functional requirements could have been discussed in response to this question;
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(6 marks) |
Question 3 Sally continues her analysis by drawing a context diagram and she has started a data flow diagram (DFD).
a. List the entities involved. 2 marks [1 line]
The two entities involved were voters and council, and most students were able to identify them b. There are three processes:
From these processes, select the correct two for the circles labelled 1 and 2 in the DFD below. Write your answers in the circles.Process 1 - Check voter eligibility and record votes Process 2 - Allocate votes to candidates Process 1 imports voter_ID_details (to check voter eligibility) and exports voting_data (to record votes) Process 2 exports individual_votes to each of 3 candidates (which is allocating votes) The two processes required in the DFD were: c. Using the context diagram, the DFD and correct labelling conventions, choose labels for the data flows numbered 3 and 4. 2 marks Voting_data You can see this in the context diagram. 4. [1 line]
Election_results Again, the context diagram shows there is only one data export from the system to the council. This is the same mystery flow in the DFD. Students should be encouraged to use the data flow diagram to assist in formulating accurate
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(6 marks) |
Question 4 The council wants to offer mobile voting to voters aged 80 and above or those who may be unable to get to the polling booth due to a diagnosed medical condition. To obtain an estimate of how many voters will require mobile voting, Sally has decided to use the council's electronic roll of eligible voters. She will create a file containing each voter's name, address, age and information on whether they have a diagnosed medical condition. The following algorithm is suggested, with Age being the age of the person in years and Medical indicating if they have a diagnosed medical condition. a. To check this algorithm before coding, the data in the table below was created. Complete the table by filling in both expected and actual values after each record is read and the loop is executed. 3 marks
This was so obvious that a thorough deskcheck may not even have been necessary. Do it now anyway - as an exercise. Many students struggled with this question – many had the correct expected values but did not [The examiner's answers match mine above].
b. Outline the major error in this algorithm. 1 mark [4 lines] If someone's age is >= 80, and they also have Medical=True the NumberEligible is incremented for each condition, instead of just once. Many students were able to identify that the error occurred because the value of NumberEligible is c. Write new lines of code to correct this error. 2 marks [9 lines] Remove both IF structures and replace with... IF age >= 80 or Medical = True then The examiners' answer is the same as mine. AVERAGE MARK 1.0 | |||||||||||||||||||||||||
(4 marks)
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Question 5 Sally has started a data dictionary of all the variables that will be used in the voting software.
Students were generally aware of the appropriate data type; however, a number failed to provide The examiners' answer is the same as mine. |
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(2 marks)
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Question 6 Choose the best data structure from the list below for the data in the voters' electoral roll:
The "in RAM" bit is essential. Arrays only apply to storage in primary memory. The examiners' answer is the same as mine. AVERAGE MARK 1.2 |
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(4 marks) |
Question 7 A member of Sally's team has suggested using a virtual private network (VPN) for sending the voting data back to the council. Communications over a VPN are very securely encrypted, so data will be safe during transit. What's a second advantage of VPN? This is quite a technical question - especially the difference between HTTPS and VPN.
Most students had difficulty with providing technically accurate information or responses were AVERAGE MARK 1.5. Told you so. |
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(3 marks) |
Question 8 The voting software will need to be accessible to all eligible voters. This includes voters with special needs, such as visual impairments, reading disabilities and physical disabilities. Visual impairments [4 lines]
Reading disabilities [4 lines]
Physical disabilities [4 lines]
Most students were able to discuss accessibility issues, with many providing a range of
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(6 marks) |
Question 9 Voters may need to update their details on the electronic electoral roll. Sally needs to be sure that all data entered into this file is reasonable. a. What is this technique called? 1 mark [1 line] Validation. A majority of students were able to identify validation as the technique described. AVERAGE MARK 0.6 b. Surnames must contain alphabetic characters and may also contain an apostrophe ('), hyphens and spaces. The field ‘Surnames' cannot be blank and no upper limit on length is set.
Most students were able to provide a range of test data; however, a number of students tested the
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(2 marks)
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Question 10 MMS has made a recommendation to the council to mail to each voter a printed copy of a simple quick start guide to assist them with the use of the online voting software. The council had assumed that all user documentation would be built into the software and this would help them to reduce printing costs.
A number of students concentrated on the inefficiency of the postal service or people’s inability to
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(2 marks) |
Question 11 In order for the election process to run smoothly, election officials will need to be trained to use the new voting software. The council will need to employ at least 60 officials to supervise voting at the polling booths. Many of these officials will be employed only for Election Day and could have other employment on other days. Online training will probably be the cheapest and most convenient. Video tutorials could be put on a password-protected part of the council website with animated multimedia explanations and electronic tests. The completion of tests, and the test results can be stored by the council to ensure officials are now qualified. The traditional methods - lecture, small-group, and train-the-trainer are not really appropriate here. Students often provided responses such as train-the-trainer or a centralised training session;
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(4 marks) |
Question 12 The data collected from the file servers at the polling booths and through mobile voting is irreplaceable. The data must be retained and must be collected even if the internet connection is lost between the polling booth file servers or the mobile devices and the main server at the council's office. 1. on the polling booth file server [4 lines]
2. on the mobile devices. [4 lines]
I'm having trouble working out what key knowledge the examiner is fishing for. Students struggled to provide clear and technically accurate responses to this question. Many
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(3 marks) |
Question 13 If this voting software is successful, it is hoped that the software will be sold and used in other larger elections. As such, it may need to allow for electoral rolls of approximately 10 million voters. Each voter's record is approximately 150 bytes. a. Calculate the file size, in gigabytes, of an electoral roll with 10 million users and explain if the file can be stored on a mobile device with 32 GB of storage. 2 marks Size of file [1 line] 1.5 GB (assuming an even 1 million bytes per megabyte) or 10,000,000 voters * 150 bytes = 1,500,000,000 bytes. Explanation [3 lines] Yes. The file can be stored on the device because 1.5 GB is less than 32 GB. This question required students to calculate the likely file size in gigabytes. A number of students b. If the mobile device has 512 megabytes of RAM, what effect is using this file likely to have on processing? 1 mark [3 lines] Processing will be slower. Because the entire data file will not be able to be stored completely in RAM, it will need to be swapped in and out to secondary storage (e.g. SD card) as needed. Accessing these non-volatile media is slower than accessing RAM, so processing will be considerably slower. The same happens with a home PC with little RAM that has to use the page file on hard disk to simulate RAM. The majority of students were able to identify that the whole file cannot be held in RAM at the same
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(6 marks) |
Question 14 Sally is concerned that during the two-week period prior to Election Day, the newly installed voting software may create conflicts for other council services, such as the council's website and IT department. a. State two conflicts that may occur. 2 marks [3 lines]
Students had difficulty expressing what conflicts may occur in this situation. Most common were b. For one of the conflicts stated above, identify the stakeholders and outline why the conflict exists. 2 marks [4 lines]
If students were able to identify a conflict, they were generally able to identify the appropriate c. Suggest two techniques that could be used to minimise the conflict discussed in part b. 2 marks
Students gave a range of techniques that could be used to minimise the conflict with IT staff, |
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(6 marks) |
Question 15 After Election Day, the council needs to prepare a list of those who have not voted. The voters' electoral roll contains a number of fields, including Surname, GivenName, StreetAddress, Suburb, Postcode and Voted. To do this, it is necessary to read each voter's details from the Electoral Roll file and display the fields Surname, GivenName, StreetAddress, Suburb and Postcode for those who are recorded as false in the Voted field. Each record is read until the EndOfFile is reached. Write pseudocode for a procedure to perform this process. [11 lines] Begin Pretty easy. Students are reminded to read the question carefully as many students read and displayed the |
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END OF QUESTION AND ANSWER BOOK |
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Created 2 November 2015
Last changed: March 9, 2022 11:35 AM
Original Content © Mark Kelly 2015
Images and questions are © Victorian Curriculum
and Assessment Authority 2015.
Reproduced here with permission for educational purposes.
Thanks, VCAA!
VCE Applied Computing Notes © Mark Kelly
Section C summary
It's a shame the pseudocode challenges were so lightweight. Kids can do better than that.
Overall, pretty fair and straightforward.