The layout of this paper is modelled on the Higher Grade Computing .... 11. A
program has been written that creates and processes the costs of 20 items. PS.
[COMP(H)06] NATIONAL QUALIFICATIONS
COMPUTING HIGHER Marking Instructions
This paper must be withdrawn from candidates after any follow-up discussion of marks/grades awarded. This is to ensure the ʻsight unseenʼ status of this paper is maintained for your centre and other schools/colleges during the diet of prelim examinations in 2005/2006. Submission of this test paper for Appeals purposes will assume that these conditions have been applied. © 2005-2006 Perfect Papers – All rights reserved.
Page one [COMP(H)06MS] http://www.perfectpapers.net
Higher Computing Marking Instructions KU - Knowledge and understanding PS - Problem solving Commentary on paper Structure of paper The layout of this paper is modelled on the Higher Grade Computing specimen paper published by SQA as part of the Course Assessment Specification. The Question Paper • consists of 3 sections • has a mark allocation of 140 marks • has a time allocation of 2 hours 30 minutes. Section I – 30 marks • consists of objective and short response questions • samples across the content statements of the two mandatory units (Software Development and Computer Systems) • 19 marks are for knowledge and understanding • 11 marks are for problem solving • the problem solving are based in familiar contexts and are of a fairly straightforward nature • candidates are expected to tackle all questions in the section. Section II – 60 marks Questions within this section • require extended responses demonstrating structuring and reasoning have varying mark allocation and therefore do not have to be of the same length. Most questions are subdivided into a number of connected parts with the marks for each part clearly indicated. • involve both knowledge and understanding and problem solving, and are set in less familiar and more complex contexts than those in Section I. • sample across the content statements associated with the mandatory units (Software Development and Computer Systems) and parts of questions, require integration of knowledge from the two mandatory units The marks for this section are split so that: • 25 marks are for knowledge and understanding • 35 marks are for problem solving Candidates are expected to tackle all questions in the section. Section III – 50 marks • this section has three sub-sections, one for each of the optional units (Artificial Intelligence, Computer Networking and Multimedia Technology) • candidates are expected to tackle all the questions within one sub-section Questions in each sub-section • require extended responses demonstrating structuring and reasoning • have varying mark allocation and therefore do not have to be of the same length. Most questions are subdivided into a number of connected parts with the marks for each part clearly indicated. • involve both knowledge and understanding and problem solving, and are set in less familiar and more complex contexts than those in Section I • sample across the content statements associated with the appropriate optional unit • Some questions, or parts of questions, require integration of knowledge from the mandatory units. Page two [COMP(H)06MS] http://www.perfectpapers.net
The marks for this section are split so that: • 17 marks are for knowledge and understanding • 33 marks are for problem solving Advice on marking Candidates should not be awarded half marks for any part of any question. This is the approach adopted by SQA markers and SQA will reduce the estimated grade for candidates where half marks have been awarded for questions. Lenient marking by centres can be a cause for invalidating centres estimates and centres are encouraged to apply the marking guidelines as stringently as possible. Perfect Papers also recommend that, where possible, candidates complete the estimate examination in one sitting to demonstrate retention of knowledge. Typical mark thresholds are shown below Band Award Percentage 1 A >=85% 2 A >=70% 3 B >=65% 4 B >=60% 5 C >=55% 6 C >=50% 7 D >=45% 8 D >=40% 9 No award highest score THEN – 1 mark Highest score = score(counter) – 1 mark ENDIF LOOP UNTIL end of array – 1 mark
PS
(d)
Should the variables used in step 4 above be called by reference or by value?
By reference – 1 mark Values are just displayed and will not be changed – 1 mark
Justify your answer.
Page thirteen [COMP(H)06MS] http://www.perfectpapers.net
No
Commentary
Source
Question
Marking Scheme
19
The first stage of the software development process is the analysis stage.
KU
(a)
Describe two methods that could be used to gather information required at this stage.
1 mark for each of the following bullet points (maximum of 2 marks) • Interviewing users of the current system or giving out questionnaires to find out how it works. • Collecting data that is used or produced by the current system. • Taking observation notes as the system operates
KU
(b)
During the implementation stage, it is good practice to make use of a module library.
1 mark for each of the following bullet points (maximum of 2 marks) • Code is pre-tested • Code is already documented
Other than to save time, give two reasons why this is good practice. KU
(i)
Name the personnel who test software.
Independent testing group – 1 mark
KU
(ii)
Name and describe three sets of test data that should be used during testing.
Normal – data that is well within the limits of what your program is expected to handle. • Extreme/boundary – data that is at the ends of the acceptable range of data • Exceptional – Data that the program is not designed to handle used to ensure that the program is robust. 1 mark for naming all sets of data, 1 mark for each description
PS
(iii)
A program takes in the test scores out of 100 of ten students. Suggest three sets of suitable test data.
1 mark for each of the following bullet points (maximum of 3 marks) • A normal set – numbers between 1 and 100 • A boundary set with 0’s and 100’s • An extreme set with numbers out with the range and other data (e.g. text)
KU
(c)
(d)
During the evaluation stage, software is evaluated for robustness. What is meant if it is said that a piece of software is “robust”?
Page fourteen [COMP(H)06MS] http://www.perfectpapers.net
•
Robust software can deal with incorrect user input without crashing – 1 mark
No
Commentary
Source 20
Question
Marking Scheme
You have been asked to write a program by a teacher that will store and process pupils grades and then generate report cards. (a)
When writing a piece of software it is advisable not to use global variables.
KU
(i)
What is a global variable?
A variable that exists throughout the entire program – 1 mark
PS
(ii)
Why is the use of global variables not advisable?
1 mark for each of the following bullet points (maximum of 1 mark) • It means that the value of the variable can change throughout the program • It makes it harder to insert modules from a module library • Any other suitable point
(b)
It has been suggested that you use a scripting language to create the software.
KU
(i)
What is a scripting language?
Used for writing small programs that enhance an existing piece of software – 1 mark
PS
(ii)
State two uses for a scripting language.
1 mark for each of the following bullet points (maximum of 2 marks) • For writing macros for general purpose packages • For adding functionality to Web pages • Any other suitable use
When designing your software you use stepwise refinement and top-down design.
1 mark for each of the following bullet points (maximum of 2 marks) • Problem is broken down in to sub problems that can then be divided up between members of a team • Sub problems are easier to solve than trying to solve the entire problem in a single go • This method aids implementation as previously used modules could be used for certain sub problems. • Any other reason
PS
(c)
What are the advantages of using these methods to design your software?
Page fifteen [COMP(H)06MS] http://www.perfectpapers.net
Section III Part A – Artificial Intelligence No
Commentary
Source 21.
Question
Marking Scheme
Consider the following statement: “Different scientists give different definitions of artificial intelligence but most agree that artificial intelligence is the study of those theories, techniques, procedures and algorithms by which we may develop a machine that can be think or show intelligent behaviour as demonstrated by humans”.
KU
(a)
Explain why it is difficult to agree on a definition of artificial intelligence.
1 mark for each of the following bullet points (maximum of 2 marks) • Difficult to agree on definition of human intelligence • different characteristics are considered importance by different scientists. • Without clear definition of human intelligence, it is impossible to define clearly what is mean by artificial intelligence
KU
(b)
Identify two characteristics of human behaviour that could be considered intelligent.
1 mark for each of the following bullet points (maximum of 2 marks) • communicate with others • Learn new knowledge • Make decisions • Perception • Explain results and actions
(c)
The development of artificially intelligent programs requires knowledge of specialist AI languages. (i) Identify one AI language that is functional.
KU
LISP - 1 mark
KU
(ii)
Identify one AI language that is declarative
Prolog - 1 mark
KU
(iii)
Describe two differences between declarative languages and procedural languages.
1 mark for each of the following bullet points (maximum of 2 marks) • procedural language defines sequences of execution whereas declarative language states rules and facts. • Order of execution is determined at runtime.
Page sixteen [COMP(H)06MS] http://www.perfectpapers.net
No
Commentary
Source 22.
Question (a)
Marking Scheme
Every year, car manufacturers pack new embedded systems into their vehicles. Tiny processors under the hood and in the deep recesses of the car gather and exchange information to control, optimize, and monitor many of the functions that just a few years ago were purely mechanical.
KU
(i) What is an embedded system?
Chips that contain instructions that control a particular device. Chips are hidden within the system itself. - 1 mark
PS
(ii)
E.g. assistance with parking. Sensors measure space between parked cars to determine if there is enough space to par the cark. 1 mark for description of any suitable application;
(b)
Describe one embedded system in a modern car.
Read the following passage carefully. In the very near future the use of intelligent robots will change our lives. Now that the very difficult practical problems of navigation have largely been overcome, intelligent robot technology has come forward as a solution for many problems the world faces today. Problems such International trade issues and improving the quality of life for the physically handicapped will be tackled using intelligent robot technology.
KU
(i)
How does an intelligent robot differ from a dumb robot?
Dumb robots are pre-programmed to perform rote tasks with little or no ability to react or change their behaviour whereas intelligent robots have complex algorithms capable of dealing with circumstances and events that are unknown to or unanticipated by the programmer, and perhaps even the capability to learn from experience and change programming and algorithms in anticipation of future events - 1 mark
PS
(ii)
Describe one problem associated with robot navigation and suggest how this has been overcome.
Eg problems associated with providing robots with ability to find their way without colliding into obstacles. This can be overcome by providing robots with stereo vision systems 1 mark for identifying suitable problem and 1 mark for suggesting solution. Max 2 marks.
Page seventeen [COMP(H)06MS] http://www.perfectpapers.net
No
Commentary
Source 23
Question
Marking Scheme
YOUNGSTER is an expert system is being developed to help doctors in general practice (GPs) diagnose illnesses and diseases in babies and young children. (a)
The components of the YOUNGSTER medical expert system are shown below. See question paper
KU
(i)
Describe the function of working memory.
Needed to store user responses and keep track of rules that have been fired. - 1 mark
PS
(ii)
Explain the importance of an explanation facility in a medical expert system such as YOUNGSTER.
E.g. explanation facility is essential if system is to provide explanation of how particular diagnosis was made. This is important in medical situations to increase in output produced. 1 mark for relevance of how or why explanation to user; 1 mark for importance in medical expert system. Max 2 marks
PS
(b)
Describe two benefits that will be gained from the development of the YOUNGSTER expert system.
1 mark for each of the following bullet points (maximum of 2 marks) • combined knowledge of expert consultants in the particular area of medicine available to GP • availability of specialist knowledge to inexperienced doctor helps confirm diagnosis made
PS
(c)
Describe one moral issue and one legal issue that could arise from the use of the YOUNGSTER expert system
Moral – what would happen if system provides mis-diagnosis that results in the death of an infant? - 1 mark Legal – who has responsibility for any misdiagnosis that the system produces? – 1 mark
Page eighteen [COMP(H)06MS] http://www.perfectpapers.net
No
Commentary
Source
Question
Marking Scheme
24
A chatterbot is a computer program for simulating conversation between a human and a computer with the aim of at least temporarily fooling a human into thinking they were talking to another person. Eliza and SHRDLU were early examples of chatterbots.
PS
(a)
The Turing test was designed as a method of determining the existence of artificial intelligence. Describe one limitation of the Turing test. You should relate your answer to the Eliza or SHRDLU systems.
(b)
E.g. only measures ability to communicate – it doesn’t measure ability to make decisions or learn. Eliza system seems to be able to sustain conversation but cannot be considered intelligent because all it does is use a look-up table. SHRDLU, although seemingly able to communicate could not think for itself nor justify its actions. 1 mark each for description of any limitation; 1 mark for relevant reference to Eliza or SHRDLU systems. Max 2 marks
One contemporary application of a chatterbot is a web-based customer relation management strategy. This type of chatterbot offers a pleasant and useful first contact to customers, and is able to deal with the most common problems or requests for information. Explain the benefits of this type of chatterbot:
PS
(i)
to customers
E.g. available 24/7 - 1 mark
PS
(ii)
to the company
E.g. increase customer satisfaction with business which could result in increased custom - 1 mark
Page nineteen [COMP(H)06MS] http://www.perfectpapers.net
No
Commentary
Source
Question
Marking Scheme
25
The managers of a shopping centre use closedcircuit cameras to monitor the movement and actions of visitors to the shopping centre. Operators observe a set of screens in the operations room that show the output from all cameras in the shopping centre. This allows observation staff to direct security staff in the centre to intervene in any situation that threatens the security of the shopping centre or its visitors. The managers would like to automate this process using a computer vision system.
PS
(a)
Describe two problems of interpreting 3D objects such as shopping centre visitors from 2D images captured from closedcircuit cameras.
1 mark for each of the following bullet points (maximum of 2 marks) • large volume of data to be processed; 2D images can be vague • 2D images only give limited information about shape and size of objects
PS
(b)
Once a 2D image has been captured it must be analysed using signal processing techniques. Explain why signal processing would be necessary in the surveillance system described above.
Eg needed to remove noise from image; to remove blurring caused by camera movement; to improve contrast; to correct geometric distortions caused by the lens 1 mark for any appropriate reason
(c)
An artificial neural system (ANS) has been developed to assist in the surveillance system. A neural network is based on the workings of the human brain.
KU
(i)
Compare a human neuron in the brain with an artificial neuron in an ANS.
Eg biological neuron receives electrical signals from other neurons whereas artificial neuron receives numerical values that represent electrical signals; A biological neuron may have as many as 10,000 different inputs, and may send its output (the presence or absence of a shortduration spike) to many other neurons. Neurons are wired up in a 3-dimensional pattern. 1 mark for any acceptable comparison
KU
(ii)
In addition to artificial neurons, ANS make use of weights and layers. Describe each of these terms.
1 mark for each of the following bullet points (maximum of 2 marks) • Weights –values used to simulate modulated electrical signals that form input to neurons • Layers – organisation of neurons. One layer get input form previous layer and generate output for the next layer
Page twenty [COMP(H)06MS] http://www.perfectpapers.net
PS
(d)
Vision systems and ANS make use of parallel processing techniques. How does parallel processing benefit these applications of artificial intelligence?
Page twenty-one [COMP(H)06MS] http://www.perfectpapers.net
E.g. systems can run faster and produce quicker results because more processors are available to carry out processing tasks. Fast processing is essential in order to deal with vast quantities of data to be processed and searched. 1 mark for description of benefit of increased speed; 1 mark for underlying need and reason for increased speed.
No
Commentary
Source
Question
Marking Scheme
26
One current research project is aiming to combine spoken dialogue technology in computer games. Such a system would make use of natural language processing techniques to allow young children to have spoken conversations with the animated characters in the games that they are playing.
KU
(a)
Which stage of natural language processing is concerned with the generation of spoken output?
Speech synthesis - 1 mark
PS
(b)
Describe two difficulties of achieving natural language processing in a speech recognition system.
1 mark for each of the following bullet points (maximum of 2 marks) • ambiguities in meaning/intention if spoken phrase is imprecise • similar sounding words/phrases can have different meanings
KU
(c)
The use of artificially intelligent techniques in game playing has had many successes and failures.
Eg Deep Blue is a chess playing game. In 1997 it managed to beat world champion. This demonstrates success because of the large search tree that must be searched in order to plan moves and counter those of the opponent. 1 mark for description of game playing program that demonstrates use of AI techniques; 1 mark for justifying in terms of success or failure.
Identify one example of a game playing program that has successfully demonstrated artificial intelligence. Justify your answer.
Page twenty-two [COMP(H)06MS] http://www.perfectpapers.net
No
Commentary
Source 27
Question
Marking Scheme
A knowledge base contains facts and rules in a game called SUSPECTS. See question paper (a)
What would be the solution for each of the following queries?
PS
(i)
? has(rev_green, revolver)
No – 1 mark
PS
(ii)
? murderweapon(candle_stick ).
No - 1 mark
PS
(b)
Does the result produced by the query in (a) part (i) above prove that the Rev Green has the revolver? Explain your answer.
No. There is no fact to confirm that Rev Green has the revolver and for this reason, the search results in ‘no’. This doesn’t mean that the Rev Green doesn’t have the revolver – he may have but the system doesn’t have any facts that tell of this. 1 mark for explanation
PS
(c)
Assuming a depth-first search is used, explain how the program would find the solution to the following query. You should use the line numbers to exemplify your answer.
Matches at 11, sub-goal suspect(X) Matches at 3, X= mrs_white sub-goal murderweapon(Y) - 1 mark Matches at 10, sub-goal weapon(Y) Matches at 1, Y = candle_stick, sub-goal is_in(candle_stick, dining_room) - 1 mark Sub-goal fails, backtrack to 10 - 1 mark Matches at 2, Y = lead_pipe, sub-goal is_in(lead_pipe, dining_room) - 1 mark Matches at 8, sub-goal has(mrs_white, lead_pipe) Matches at 6, output X = mrs_white - 1 mark
? is_guily(X)
PS
(d)
Rule 11 in the knowledge base makes use of a feature known as inheritance. Explain one advantage of inheritance.
Page twenty-three [COMP(H)06MS] http://www.perfectpapers.net
Inheritance reduces memory needed to store rules in knowledge base since nodes adopt characteristics of their descendants 1 mark for advantage; 1 mark for explanation.
No
Commentary
Source 28
Question
Marking Scheme
ESCOTIA Airlines has a number of flights that fly direct from Glasgow airport to various locations throughout Europe. A customer would like to book a flight with ESCOTIA airlines from Glasgow to Rome. Since there are no direct flights, the customer will need to use a combination of connecting flights. A search tree shown below has been drawn to show the flight connections available. See question paper
PS
(a)
Compare breadth-first and depth-first search techniques by referring to the need for backtracking in each method.
All search techniques involve backtracking. DFS requires considerable backtracking when long branch with no decision at the end is explored; BFS can require considerable backtracking when the solution is several layers deep. 1 mark for use made of backtracking in each technique. Max 2 marks
PS
(b)
Suggest a suitable heuristic that could be used to help find the best route for the customer from Glasgow to Rome.
E.g. look for lowest cost or fastest connection times - 1 mark
Page twenty-four [COMP(H)06MS] http://www.perfectpapers.net
Section III Part B – Computer Networks No
Commentary Question
Marking Scheme
29.
A family with young children have just purchased their first PC. The parents are concerned about their children having access to unsuitable material.
PS
(a)
One internet service provider (ISP) offers a walled garden. Explain how a walled garden could help ensure a safe experience for the children.
The internet user is only able to access sites that have been specifically approved by the ISP - 1 mark Sites are selected on their appropriateness, ie no nudity, sex, racism, or other offensive content, making it suitable for user and their family to access - 1 mark
PS
(b)
Another ISP the family have considered does not offer a walled garden, but is able to provide software which they advise the family installs to minimise the risk of access to unwanted material. Describe three types of software they may provide the family with.
1 mark for each of the following bullet points (maximum of 3 marks) (No description – no marks.) • Firewall – prevents their computer being ‘seen’ by other internet users and being attacked by others • Pop-up blocker –minimises the amount of undesirable sites/images being presented to the user (and innocently clicked on) • Anti-spam software – minimises users opening up e-mail which contains unsuitable content or links to it • Anti-virus software – minimises the risk of a file being loaded onto their computer or executed, which can subsequently present the user with unsuitable images or try and redirect them to such sites
(c)
The parents have been told of advantages of online shopping. Despite this, they remain cautious about the idea.
KU
(i)
Give two concerns they may have about online shopping.
Other users being able to ‘see’ their credit card details – 1 mark Details being passed on to other sites or companies – 1 mark
PS
(ii)
What advice should they follow to be assured about these concerns.
Check that their details are being entered into a secure site, indicated by a small padlock at the foot of the browser and https in the address bar 1 mark Tick all boxes which ask for permission for the users’ data to be passed onto other sites - 1 mark
Page twenty-five [COMP(H)06MS] http://www.perfectpapers.net
No
Commentary Question
Marking Scheme
30.
A local group of volunteers have set up a website to promote the various attractions of the town of Esselmont.
PS
(a)
The group have bought the domain name www.esselmont.org.uk for their site. Explain what each part of the name refers to.
www – the name given to the company’s web server esselmont – the name of the organisation or company (or name chosen by the body to identify it on the world wide web) org – the type of body, in this case identifying that the site belongs to an organisation uk – denotes where the company (or server) is based 2 marks (1 mark deducted for any error/omission)
PS
(b)
How else could an internet user directly access the website?
By entering the DNS address in the browser’s address bar. 1 mark
PS
(c)
Explain how the group’s domain name can be matched up to the correct IP.
DNS clients send a named address to Domain Name Servers. These servers store information which matches valid names with their IP addresses. Once matched, the server returns the associated IP address. If one DNS does not have a match for the name, it may refer the name to another DNS. If not found, an error appears on the user’s browser indicating that the server could not be found. 2 marks (1 mark for less detail)
PS
(d)
The group have rented a small office where they intend to network half a dozen PCs. Which class of IP address would they use to do this and why?
Class C - 1 mark Classes A and B are used for larger organisations, companies or ISPs. Class C uses 8 bits for local addressing which offers a sufficient number of IP addresses for a network with scope for future growth - 1 mark
PS
(e)
Some companies have recently found themselves victims of a DOS attack. Explain what this is and what can be done to minimise the risk of being attacked.
A Denial Of Service attack is one where a company’s servers, or resources including hard disk drive, network connections, are put under pressure in a way that prevents other users being able to access them. 2 marks (1 mark less detailed) The risk of DOS attacks can be minimised by installing a firewall, which monitors incoming and outgoing traffic. Up-to-date anti-virus can prevent the use of worms for triggering a DOS attack. 2 marks for detailed solution (1 mark for less detailed)
Page twenty-six [COMP(H)06MS] http://www.perfectpapers.net
PS
(f)
The local group are considering using fault tolerance components to minimise risk of disruption due to a system failure. Describe one example of a fault tolerance component and say whether or not you feel it would be appropriate.
Examples include: RAID system – series of mirrored hard disks, whereby if one drive fails, any of the others can be accessed, allowing the system to continue operating. Appropriateness – good, in that the system can continue operating in the event of a hard disk failure. Clustering servers – a group of servers on a network where if one fails, any of the others can take over. Appropriateness – probably not appropriate as the company may not likely have two or more servers for their size of their business at present. UPS – Uninterrupted Power Supply which will prevent a server from crashing in the event of a power failure. It will allow enough power to have the file server notify all users, safely close down its applications and data files before shutting itself down. Appropriateness – good in order to minimise the loss of any data in the event of power failure to the server. 2 marks for description of a suitable component 1 mark for sound argument regarding its suitability
Page twenty-seven [COMP(H)06MS] http://www.perfectpapers.net
No
Commentary Question
Marking Scheme
31. KU
(a)
List three things that distinguish WML from HTML.
1 mark for each of the following bullet points (maximum of 3 marks) Compared with HTML: • WML has fewer formatting features, supporting the more basic ones such as bold, italic and underline. • Has limited support for tables and images • Used a data structure where content is stored on cards.
KU
(b)
Why are many WAP enabled devices unable to access HTML content?
1 mark for each of the following bullet points (maximum of 1 mark) • Many of the devices have slow connection. • Limited data input options. • Screens too small.
KU
(c)
A company has bought a number of PDAs. They are able to communicate through a WPAN. Give one example of a type of wireless communication, giving typical speed and range of communication.
Example: Bluetooth Speed: 720 kbps (versions 1.1 & 1.2), 2 Mbps (version 2) Range: 10 m (class 3), 20 m (class 2), 100 m (class 1) Example: IrDA Speed: 5760 kbps & 11520 kbps (version 1.1), 2400 kbps & 11520 kbps (version 1.0) Range: 1 m 1 mark for type 1 mark for speed and range
KU
(d)
A company wishes to install a network within a listed building, but have been denied permission to run cables behind walls. What hardware will be required to allow the computers to communicate wirelessly.
Transceiver - 1 mark Wireless network card - 1 mark
PS
(e)
Explain why a MAC address is needed when transferring data over a network.
The MAC address is the unique physical address which allows a device (or node) on a network to be identified - 1 mark AND Nodes will can only accept and process data by checking the MAC address attached to the data. OR Routing tables are constructed by routers using MAC addresses 1 mark for either of the above two points
Page twenty-eight [COMP(H)06MS] http://www.perfectpapers.net
PS
(f)
Some companies operate a policy where all user communication is monitored. Say whether or not you think this is justified and give reasons for your answer.
Justified: 1 mark for each valid reason (maximum of 4 marks) • All computer data should be monitored in the interests of national security • Businesses have to ensure that their facilities are not being abused • Companies must have a way of identifying those responsible for inappropriate conduct • It is the law! The Regulation of Investigatory Powers Act 2000 allows the government to intercept or acquire communications and to set up surveillance. • (Other reasons) Not justified: 1 mark for each valid reason (maximum of 4 marks) • Businesses have the right to confidentiality of their data, for example, plans and financial details. • Users themselves have the right to privacy in their communications, particularly personal e-mails. • Users have the right to have all personal data such as financial information kept private. • Against the principles of freedom of speech. • (Other reasons)
Page twenty-nine [COMP(H)06MS] http://www.perfectpapers.net
No
Commentary Question
Marking Scheme
32. KU
(a)
The OSI model is a set of protocols used for the transmission of data across computer networks. Which layer is responsible error checking and correction?
Data link layer - 1 mark
KU
(b)
Cyclic Redundancy Checking is a method used for checking errors. Explain how this works.
The binary number (representing the data) is divided by another pre-determined number to generate a remainder. The remainder is then sent along with original data - 1 mark The receiving computer performs the same calculation to generate a remainder and the two results are compared - 1 mark If different, the receiving computer requests the data to be re-transmitted - 1 mark
PS
(c)
When sending and receiving data it is important that the devices know when to send and receive data. Describe two different ways this can be done.
Synchronous Transmission – the clocks of the sending and receiving computers are co-ordinated. This co-ordinated clock pulse ensures that data is transferred at regular time intervals. 2 marks (1 mark less detailed) Asynchronous Transmission – no clock involved. Blocks of data are surrounded by start and stop bits. Individual characters also have start and stop bit. The use of these enable the receiving computer to distinguish the start and end of data. 2 marks (1 mark less detailed)
(d)
The CSMA/CD protocol is used to prevent collisions occurring during the transmission of data over a network.
KU
(i)
Explain how this operates.
When a node is ready to transmit data, it listens to find out if there is already data being transmitted - 1 mark If all is clear, the node sends the data, as can others in the network - 1 mark If there is a collision between data sent by two nodes, both wait a random amount of time before resending their data - 1 mark
PS
(ii)
Why can the use of CSMA/CD sometimes have a detrimental effect on network performance?
The more nodes there are on the network, the more likely there will be a collision, so the longer it can take for data to be received by the required computer - 1 mark The further apart the nodes are, the harder it is for the nodes to detect other transmissions on the network - 1 mark
Page thirty [COMP(H)06MS] http://www.perfectpapers.net
Section III
Part C – Multimedia Technology No
Commentary Question
Marking Scheme
33.
A web page is being created for a school. The web site is intended for members of staff, the parents of the pupils in the school and the pupils themselves.
PS
(a)
Suggest a plan that would allow the necessary information to be gathered before the design phase takes place.
1 mark for each of the following bullet points (maximum of 2 marks) • Compared with HTML: • Analysis needs to take place, where the problem to be solved is investigated to identify need. • The plan detail will vary but may include: • Interviews with senior management – small group. • Questionnaires to parents/pupils – large group.
KU
(b)
During the design stage of the website, the screen layout of the pages is determined. Describe one technique that may be used to create the layout of the web pages.
1 mark for each of the following bullet points (maximum of 2 marks) • Storyboarding provides a detailed description of the final product. • Contain information on text, graphic, video, sound, audience interaction, type fonts, type size, etc.
(c)
Artwork created by an S1 pupil is to be included on the web-site. The artwork is scanned and saved as a compressed 24-bit. The image is shown.
KU
(i)
PS
(ii)
Explain the type of compression that will be used on this image.
Run Length Encoding – 1 mark Algorithm looks for a repeated pattern of pixels replaces with a number and the pixel colour - 1 mark
The edges of the image are seen as jagged and need to be made smooth.
Anti-aliasing – 1 mark Adds a line of an intermediate colour between the two existing colours to give the impression that a smooth edge exits - 1 mark
Explain one technique that may be used to solve this problem.
Page thirty-one [COMP(H)06MS] http://www.perfectpapers.net
PS
(iii)
Based on you solution in part (ii), it has to be decided whether to apply this technique to the image before it is included on the web site. You have to decide whether to apply the technique or not. Give one reason to justify your decision.
Sample answers should be based on the impact the image has on the web page. Examples may be: • As the image may appear blurred at the edges, the image may appear sharper on the web site if the technique is not applied. Smoother image integration into the web page may make technique appropriate 1 mark for correct reasoning rather than yes or no to applying anti-aliasing.
Page thirty-two [COMP(H)06MS] http://www.perfectpapers.net
No
Commentary Question
Marking Scheme
34.
A head of a local council department is preparing a talk to his staff and decides to create slides to support the talk.
PS
(a)
PS
(b)
(i)
Identify a suitable application package purpose.
class of for this
(ii)
Give two reasons why your choice of package is suitable.
Presentation software – 1 mark
Linear nature of presentation matches speaker delivery. – 1 mark Ability to include wide range of media types e.g. sound, video, text – 1 mark
As part of the presentation he wishes to include sound files. The sound files are the spoken words from politicians and famous people that he feels are inspirational. When the voice is recorded the sound wave looks as shown. As part of the presentation he wishes to include sound files. The sound files are the spoken words from politicians and famous people that he feels are inspirational. When the voice is recorded the sound wave looks as shown.
PS
(i)
Explain what has happened to the sound file.
Sound recording carried out with volume set too high – 1 mark
KU
(ii)
Name this effect.
Clipping - 1 mark
Page thirty-three [COMP(H)06MS] http://www.perfectpapers.net
(c)
The head of department decides to record his voice for use on certain parts of the presentation. He records the file using a microphone plugged into the sound card.
KU
(i)
Describe the role of the sound card in the capture of the head of department’s voice.
1 mark for each of the following bullet points (maximum of 3 marks) • Input signal goes to Analogue to digital converter chip [Changes the analogue signal to digital signal] • ADC sends the binary information to the digital signal processor. • DSP gets instructions from a ROM chip about what to do with signal e.g. compress signal [ROM chip contains the instructions to handle the digital signal]
PS
(ii)
The manager decides that the file will be saved as a WAV file.
1 mark for each of the following bullet points (maximum of 2 marks) • Compresses stored PCM values - Stores changes in values rather than values themselves • File format is common and may be inserted in a variety of application packages.
Justify the choice of saving the sound as a WAV file, giving two supporting statements. (d)
The presentation will include 4 music files as background music. When one of the files is recorded the waveform looks like the one shown.
KU
(i)
What should be done to this waveform before it is included in the presentation?
Normalisation - 1 mark
PS
(ii)
Explain why this important in terms of the presentation.
One file may sound louder than others if the files are not normalised, causing listening difficulties turning volume up and down. - 1 mark
PS
(e)
The sound file is a stereo music file lasting 30 seconds using CD quality. Calculate the storage space required for this file. Give the answer in Mbytes.
Page thirty-four [COMP(H)06MS] http://www.perfectpapers.net
No of bits = channels * no of bits * sampling depth * length of track – 1 mark = 2 * 44100 * 16 * 30 bits = 42336000 bits – 1 mark = 5292000 bytes = 5167.97 Kbytes = 5 Mbytes – 1 mark
No
Commentary Question
35.
Marking Scheme
A television company are looking to deliver video advertising latest films to their customers. The programmes are transmitted via satellite or cable. The company link extracts from 8 of the latest movies in a short film that repeats continuously on the film channel before movies are shown. A computer system and video editing software are used.
PS
(a)
Explain two ways in which the video editing software may be used when the short film is created.
1 mark for each of the following bullet points (maximum of 2 marks) Examples of functions are: TIMELINE • Ability to place, edit and remove objects on timeline to determine order and timing of play. • May allow recording of narration, trimming of clips, adjusting of audio levels, etc. TRANSITION • Controls how the video plays from one clip to the next. SEQUENCING • Order of the 8 clips can be determined and changed as required simply by moving clips on e.g. a timeline. Answer should relate to the scenario and the 8 clips being brought together.
(b)
The short film is saved on DVD and played back to check the visual impact of the presentation
PS
(i)
Recommend one suitable technique for storing the short film clip.
Uncompressed AVI • Container format • Contains both video and audio data • Audio-video interleaving rate can be set MPEG • Video and audio compression based on discrete cosine transform [DCT] • Each frame is compressed as a JPEG • Stores a key frame and subsequent frame contains data on changes from key frame. 2 marks for a suitable description of the process containing two discrete points– either uncompressed AVI or MPEG description is suitable
Page thirty-five [COMP(H)06MS] http://www.perfectpapers.net
KU
PS
(ii)
(c)
State clearly the role of the components of a video card when the video is played back.
It is decided to include background music for the presentation. It is suggested that surround sound or stereo sound is used to deliver the music. Compare the suitability of using stereo sound or surround sound in the presentation. You should use two supporting statements.
1 mark for each of the following bullet points (maximum of 2 marks) • GPU may be used to decompress the file for playback using software or chip with appropriate CODEC. • Audio/video data is sent to the digital to analogue converter, which converts the digital data to analogue 1 mark for each of the following bullet points (maximum of 2 marks) Surround Sound • Provides a more life-like immersive experience for a user, providing more suitable audio cues to the user. • Data requires to be compressed in order that playback hardware is able to cope with number of bits requiring processed. • Requires data for 5 channels • Requires non-standard equipment to playback Stereo sound • Standard computers provide this capability. • Smaller file size as only 2 channels 1 mark for each of two suitable points. Maximum 2 mark.
PS
(d)
The television company’s management decide to use the short film as advertising on mobile devices including phones. The video cannot be used in its present format. State two changes that may be made to the video that may allow it to be viewed on the mobile devices.
Page thirty-six [COMP(H)06MS] http://www.perfectpapers.net
1 mark for each of the following bullet points (maximum of 2 marks) • change resolution • change colour depth • change frames per second
No
Commentary Question
Marking Scheme
36.
Melanie is looking to buy a new camera to help her create a multimedia product as part of her Biology course.
KU
(a)
Describe the type and role of the Charge Couple Device (CCD) in a digital camera.
•
An array CCD is used in a camera. o Strips of CCD cover entire picture area. o Coloured filters cover the array [RGB] o data passes to ADC to convert to digital.
1 mark for naming correct CCD 2 marks for description which may break down to: • 1 mark for strip cover, • 1 mark for colour filters over array PS
(b)
The salesman at her local shop she is offers her a 5 megapixel camera or a 3 megapixel camera that claims to produce images that are twice the resolution of the Charge Couple Device (CCD) rating.
• •
Re-sampling is used. The software ‘guesses’ the actual colour using the colours of the pixels around it.
1 mark for naming 1 mark for how it gets the new colour.
Explain one technique that may be used that may allow the second camera to produce an image that is twice the size of the Charge Couple Device (CCD) rating. PS
(c)
Melanie begins to use her camera and is getting familiar with the settings for photograph quality. She finds that she has two settings to save the picture: JPEG and TIFF. Which file format would you suggest that Melanie chooses from her camera’s setting: JPEG or TIFF? Support your answer with two reasons.
TIFF • Stores raster images including photographs and line art • Popular format for high colour 32 bit images • Widely used in image manipulation software • Uses lossless compression • Unlike JPEG, can be edited and saved without a compression loss. • JPEG • Lossy format for compression • Full colour format and relatively small file size • Degradation of image may occur with repeated editing and saving. Marks to be awarded for reasons rather than choice. 1 mark for each reason to a maximum of 2.
Page thirty-seven [COMP(H)06MS] http://www.perfectpapers.net
No
Commentary Question
37.
(a)
Marking Scheme
Dan Druff is creating a background for his mobile phone. Dan experiments with his graphics package. He experiments by drawing a rectangle then a circle on the same layer (Figure 1). Dan decides to edit the rectangle and brings it forward (Figure 2).
PS
(i)
Explain whether Dan is using a vector graphics package or a bitmap graphics package.
As the rectangle can be brought forward the package is a vector graphics package. 1 mark for explanation not naming of type of package.
KU
(ii)
Describe how these objects are stored in the package Dan is using.
the attributes of the object are stored e.g circle [ centre, radius, fill, line thickness, line type, etc] 1 mark for description.
KU
(iii)
Describe two types of tool that are available in this type of package.
1 mark for each of the following bullet points (maximum of 2 marks) • line tool • pen tool • rectangle tool • text tool • freeform tool
PS
(b)
PS
On completing the background image, Dan decides to create a new ring tone for his phone using MIDI software on his home computer. (i)
Identify two benefits of using a MIDI file in connection with the new ring tone, giving reasons to support each benefit.
1 mark for each of the following bullet points (maximum of 2 marks) • small file size • may be edited in a text editor on phone
(ii)
Dan plays the MIDI file to check it sounds as he wishes it. Explain one way in which the sound card will play the created MIDI file.
Wave table synthesis - 1 mark AND 1 mark for each of the following bullet points (maximum of 1 mark) • MIDI instruction tells DSP which sound to play. • DSP looks up sound in ROM table if wave table • DSP manipulates stored sound to generate correct sound if required • Passed to DAC for conversion to analogue signal.
Page thirty-eight [COMP(H)06MS] http://www.perfectpapers.net
(c)
A friend of Dan suggests that he uses 3-D graphics for the image in the background. He creates the 3-D graphic using an application package.
PS
(i)
Identify the file type of the saved file.
Scaleable Vector Graphics – 1 mark
KU
(ii)
Give one benefit of using this type of graphic file.
1 mark for each of the following bullet points (maximum of 1 mark) • attributes only stored • edited in text editor • may be produced from an application package
Page thirty-nine [COMP(H)06MS] http://www.perfectpapers.net
