This is default featured post 2 title
Go to Blogger edit html and find these sentences.Now replace these sentences with your own descriptions.
This is default featured post 3 title
Go to Blogger edit html and find these sentences.Now replace these sentences with your own descriptions.
This is default featured post 4 title
Go to Blogger edit html and find these sentences.Now replace these sentences with your own descriptions.
This is default featured post 5 title
Go to Blogger edit html and find these sentences.Now replace these sentences with your own descriptions.
Showing posts with label HSC. Show all posts
Showing posts with label HSC. Show all posts
Monday, February 14, 2011
Wednesday, February 9, 2011
Chapter 1.12 Implications of Computer Use
Chapter 1.12 Implications of Computer Use.
1.12 (a) Changing Trends in Computer Use
Imagine two people who live in a village. The village has a shop and newsagent. The last bank in the village has closed because it was too costly for the bank to maintain the branch which was losing money because so many of the villagers had changed to running their account on the Internet. A person living in this village that has a computer connected to the Internet will be able to pay their bills, order goods from the supermarket 20 miles away at a lower cost than buying them from the village shop and will have a wider variety of choice from the supermarket than they could get locally. They will be able to book rail tickets, at a discount, through the Internet, which will also allow them to pick up holiday bargains.
The second person does not have a computer, so has difficulty with having a bank account, has to use the village shop with much higher prices, and does not have the convenience of ordering on the Internet. If they want to book a holiday there is a 40 mile round trip to find a travel agent in the nearest town. These two people are very different in their life styles and the social changes that have occurred to, not just one of them, because of the computer are immense.
When we add to this the fact that one of these people used to be employed by the bank to run the branch in the village, but is now out of work, while the other has been told to go on a training course to learn a new piece of software, the scale of how much our lives are being effected by the use of new technology becomes even more evident.
1.12 (b) Changes in Leisure and Work
Computer availability and acceptance has brought about large changes, not just in the ways that we live, but also in the way we use our leisure time and in work practices.
Children, particularly boys, spend long hours of their leisure time in front of computer terminals playing computer games. This is a very insular way of passing the time which is beginning to worry educational psychologists because children who behave like this are in danger of not forming the social bonds and learning about the social interaction necessary in later life. Some of the games are particularly violent, or anti social. Although there is no hard evidence of a link between playing such games and anti social behaviour of the child themselves, there is a growing belief that there is such a link. Long hours spent in front of the monitor screen at an early age is suspected to cause the growing amount of RSI and other injuries being suffered by young adults, many years before their parents generation would have shown such symptoms.
Work practices are changing in a number of ways.
· Computers have meant that some repetitive tasks have been taken away from human beings. A robot on a car production line can not only work more consistently than its human counterparts and do the jobs of many people but it does not need paying. Many jobs have been lost to the human work force in this way. However, companies that have invested in this way have tended to become more profitable which has the effect of safeguarding the jobs that are still offered by the company, and also leads to expansion and the creation of additional jobs.
· Additional jobs are created. Every time a robot is placed on a production line, someone has to build the robot, someone has to write the software to control it and someone has to maintain it. The problem is that the majority of jobs created require more skills than the jobs that have been lost. This in turn means a ‘skilling up’ of the workforce. This change in working practices is another example of the technology creating two classes of people (Section 1.12.a), those able to learn additional skills and those not.
· The use of technology allows people whose jobs require a desk and who can communicate satisfactorily with their colleagues without needing to be in the same physical environment to have their desks where ever they want by using electronic means of communicating. This means that people can work from home for at least part of their week. The implications are far reaching. Less pollution because of fewer commuters and pleasant working conditions are both positive factors. Less positive is the ability of the electronic systems to report the working practices of the workers to their boss, and the lack of social contact which is so important in maintaining job satisfaction.
· In the past it would have been quite normal for a person to start a job after leaving full time education and to stay in that job until they retired. Although this may be seen by some as being an uninviting prospect, it does provide for security and gives automatic prestige to even the lowliest of workers because of their seniority within the business bringing invaluable experience. This type of work practice is becoming less and less common as modern technology changes products, manufacturing techniques and the life cycle of businesses.
· Electronic communications have changed the way that business is done. Communication can be immediate, and the worker is never far from being contacted and consequently can be at work at all hours of the day. A good example is the world’s stock markets. Twenty years ago, each country had its own stock market, the performance of which might affect others when they opened, but they tended to be fairly insular in their dealings. Nowadays, the stock markets of the world are all interconnected. As a stock holder it is possible to buy and sell stock at any time of the day or night simply by using one of the markets open at the time, no longer is it necessary to wait for the national market to open the following day.
1.12 (c) Privacy and Confidentiality of Data
The expansion of computer systems around the world has given rise to more information being stored about individuals than ever before. The problem is that to get another copy of a person’s information the only thing that needs to be done is to press a button. Distance is no object either. Using electronic communications it is possible to send a person’s information from one side of the world to another in milliseconds and then to store that information in a system that the owner of the information is unaware of.
There would be no problem if it could be ensured that all the users of the information were going to use it for the right reasons and that the information was always accurate, however these things cannot be guaranteed. Consequently it has become important to protect individuals from misuse of their information by legislation and by measures that restrict both the access to the data and the passing on of the data to other users.
Unfortunately the use of electronic information does not recognise national boundaries and some authorities are not as anxious to uphold the rights of the individual as others. A typical effect of this passing on of personal information is the junk mail that comes through the letter box. An interesting experiment is to change your initials every time you have to give your name. Within a relatively short space of time junk mail will begin to arrive and by reference to the initials it is possible to work out who has sold your details on and to whom they have been sold.
1.12 (d) Legislation
Legislation protecting personal information must not be confused with copyright law. Copyright law protects intellectual property, in the case of a computer system it would protect the person who has written the software rather than the user or the person whose details are being stored. Each country will pass laws that are particular to that country, but they largely follow the same model that is used in Britain.
Any personal data that is stored in a computer system must
· be accurate and up to date.
· be relevant to the task for which it is intended to be used and used for that original purpose.
· not be kept longer than is necessary.
· be kept securely. Access to the data must be strictly controlled.
· be available, on request, to the subject of the stored data.
1.12 (e) Controversial Information
The Internet was originally started by the American military (ARPANET) as a means of communication in time of war. The principle was that if a communications system has a central control system (like a telephone exchange) then it is easy to disable that communications network by destroying the central control. There can be as many telephones as you like, without an exchange they are useless. ARPANET was devised so that there was no central control and consequently the losing of one part of the system does not stop the rest of the system from operating.
This is the whole principle of the Internet, there is no control. When someone complains about the fact that there is a page on the Internet that shows anyone how to make a bomb and says something like, “They should have that page removed.” They are showing their lack of understanding of the net. There simply is no ‘They’, there is no one in charge. A major problem is that individuals find it impossible to agree about what should be available on the net and what should not.
1.12 (f) Health and Safety Implications
The human being is not a sedentary animal. The human body is not designed for long periods of inactivity. The body is designed to move. The legs are designed to move us around, the arms to carry things and support weights, the eyes are designed for 3 dimensional vision. We are not designed to sit for long periods of time, supporting the weight of our own arms while small movements are made by the hands to press keys and our wonderful 3 dimensional sight is used to stare at a flat screen no more than a metre away.
The human body is very resilient, but, as with any misuse of the body the long term use of computer systems in this way will cause damage.
Muscles that are not designed to support relatively small weights (the arms) for long periods of time when using the computer keyboard begin to be strained, particularly when such small movements are made. Joints in the fingers and the elbow and shoulder are made to perform movements that they normally would not do, and to perform them regularly over long time periods. Over time, these strains on the body can lead to pain and to restrictions on movement which are difficult to ignore. A new condition has been identified called repetitive strain injury (RSI). The simple cure for this is to take regular short breaks and to move around and exercise the joints and muscles. Also helpful is the use of a Natural Keyboard which allows the user to sit naturally while working.
Eyes did not evolve to stare at a flat surface that is very close for long periods of time. The eyeball should, naturally, move about in the socket. This produces tears which lubricate the eyeball. Too much enforced staring at one point can lead to a condition called dry eye which can be very painful. The eye can also tire because it is being made to use a fixed focus for long periods. The use of glasses to help the eyes to remain focussed and regularly looking away from the screen can help to alleviate these problems, as can the use of anti glare screens fitted to monitors to cut down the levels of contrast so that the eye can handle it better.
Despite the problems that are associated with the computer itself, the most important problems are less to do with the machines themselves.
Many computer installations are housed in rooms that were not designed for such use. The result is that cables are left trailing and that the furniture used is not always suitable. Many schools provide good (or bad) examples of this, where a new network has been bought with little thought for the classroom that it is going to be squeezed into. Are there enough plug sockets or are too many pieces of electrical equipment going to be run from too few sockets? Can the cabling be put in trunking? Is there adequate ventilation and is the lighting suitable? If the lighting is the ordinary classroom lighting then it will make the screens even more prone to glare. If the chairs are not comfortable then back problems can occur. These can be lessened by using ergonomically designed seating which encourages good posture.
Working with computers can cause stress, particularly among workers who were not originally trained to use them. Historically, once a worker has attained middle age they should be more experienced than the younger people coming in to the firm who will probably be working under them. This situation has changed for many people because of the use of computer technology. Because of the need to keep up to date with the latest hardware and software it is now the young people coming into the firm that are more experienced than those who have been there some time. This can lead to feelings of inferiority and stress on the older workers.
Environmental Issues
Ø A lot of paper is required for printing jobs. Hence, lots of trees are cut down.
Ø A lot of toxic gases are emitted when chips are manufactured.
Ø When computer parts are thrown, this may cause pollution.
Ø If ink cartridges are not disposed off properly, pollution may occur.
Example Questions
1. Discuss the implications for customers of a travel agent closing down their agencies and doing all their business on the Internet. (6)
2. Describe two ways in which a computer system in the home can alter the interaction of the family with the outside world. (4)
3. State two reasons why it is necessary to protect the confidentiality of information stored about people. (2)
4. Describe three measures that would be expected in a country’s data protection legislation. (6)
5. Describe the consequences of allowing upper school pupils to use the Internet to find information for project work. (4)
6. Outline the health problems that may be experienced by telecall operators and state how such problems could be overcome. (6)
7. Describe two ways in which the use of computer systems in business has harmed the environment. (4)
Chapter 1.11 Characteristics of Information Systems
Chapter 1.11 Characteristics of Information Systems
1.11 (a) Passive and Interactive Information Systems
An information system is a system that provides information according to a user’s requests.
Passive information systems.
Passive information systems are systems that will answer queries based on the data that is held within them, but the data is not altered. A simple example would be an electronic encyclopaedia where queries can be used to search for data and much valuable information can be learned, but the user is not allowed to alter the data. Another example would be the student file in a school that can be accessed by members of the teaching staff to find out where a student is at a particular time of day, or to look up their telephone number in order to contact the parents. The database of information is a valuable resource but it is not possible for an ordinary teacher to alter it.
Interactive information systems.
An interactive system is one in which data can be entered for processing, which may alter the contents of the database. An example would be the school secretary updating the attendance record of a pupil in the pupil file. In commerce, a stock control system in a supermarket is an interactive information system because it not only gives information like the price and the description of the goods for the till receipt (passive), but also updates the number in stock immediately (interactive) so that when the next item is sold the number in stock has already been altered.
1.11 (b) Management Information Systems
A management information system is software that allows the managers within a company to access and analyse data.
The management within a company, or any other organisation, is usually working on two levels. These levels may be different levels of management or may be the same people but with two different tasks. One is the day to day management of the organisation, keeping track of invoices, ensuring that the business has enough stock, arranging for the workers to be paid… The other is the strategic management, making decisions about what items of stock to keep, what new items to stock, what to discontinue…
The first of these management tasks is condition driven. The information system can be used to trigger decisions that have to be made. A certain item is reported to be low in stock by the system, requiring a decision to be made as to whether to reorder and how many to reorder.
The second of these management tasks is to look at the wider picture. To extract information from the system which can inform wider decisions like should an item be stocked, which areas of the business are doing well and which are not, which workers are having to do a lot of overtime which may point to the need to increase staff in that sector.
Such reports are termed Strategic level reports because they inform the executives who need to decide the strategy that the company is to follow.
1.11 (c) Applications requiring Batch Processing/Rapid Response
Batch processing.
A batch processing system is used when the output does not have to be produced immediately. Other factors are that the application will tend to use a large amount of data, that processing will tend to be of the same type for each set of data and that human intervention is not necessary. In section 2 we saw that the perfect example of batch processing is the payroll system, and nothing has changed because we are in a different section.
Rapid response processing.
Real time processing can be thought of as being used in process control where the results of the process are used to inform the next input. A good example would be the control of a robotic machine on the production line. The other example is in information systems where it becomes necessary to update the file of information before the next enquiry is dealt with. The classic example is the airline (or theatre) booking system. If a customer enquires whether there is a seat available on the flight, and in response to a positive reply decides to buy the ticket, then the number of tickets now available must be updated before the next person makes an enquiry, otherwise the second person may be sold the same seat. Similarly, the mail order company will need to change the number of items in stock before the next query arrives.
1.11 (d) Expert Systems
An expert system is one which contains as much data as possible about a restricted knowledge area. The data is collected from as many expert sources as possible and stored in the system, in this way it is hoped that the system contains all the knowledge about that topic that there is.
For this reason, these systems are sometimes called knowledge systems. The use of expert systems relies on the belief that for any given area of knowledge there are rules that always apply to that knowledge and that they can be applied according to a logical ordering. This can apply to scientific principles well, for example if there is a rule that oil is always found between two particular types of rock strata, then if the system identifies the strata it can determine, according to the rules, where to drill for oil. Because it follows scientific principles, oil exploration is a good example of the use of expert systems. It is particularly useful because the data that is collected is logged on computer systems when it is collected so it seems sensible to use this information as input to the expert system because it is already in computer readable form.
Expert systems need four parts in order to produce sensible results:
· A lot of data. This is all the data that the system has been told about the application area. It is called the knowledge base. Imagine a medical expert system. The knowledge base would be created by collecting all the knowledge about diseases from all the best doctors in their fields.
· A set of rules that apply to the situation. “If the patient has a headache then they should take two aspirin”. This is called the rule base.
· It is no good having a set of rules and a big collection of knowledge if there is nothing that can apply the rules to the knowledge to come up with sensible solutions. The thing that does this called the inference engine. This is what decides whether the patient should be given aspirin. Some people are not allowed aspirin, certainly not if the patient has an ulcer or…, it is the inference engine that checks through everything to find out what will fit all the rules.
· After a decision has been made, the system must be able to tell the person what the result is. The fourth part of the system, therefore, has to be an HCI.
Example Questions
1. Explain the difference between a passive information system and an interactive information system, giving an example of each. (4)
2. A company payroll system uses a personnel file among others.
a) Explain the difference between batch processing and rapid response processing. (2)
b) Explain how batch processing and rapid response processing can both be sensibly used in the context of the personnel file being used to calculate the payroll. (4)
Chapter 1.10 Designing the User Interface
Chapter 1.10 Designing the User Interface
1.10 (a) Importance of Good Interface Design
However complex the software, however expensive and powerful the hardware, the system is unusable if there is no intuitively simple to use interface with the human being who is in control of the system or for whom the system is producing results.
The HCI must be unambiguous, allow the user to input all the data that the user thinks important, and produce the output in an easily understandable form.
The intended user of the interface must be taken into account. The interface design for a pre school playgroup to learn about numbers is going to be very different from the design of an interface for the manager of a chemical plant to keep a check on the reactions around the plant. The interface that this manager would use to study a particular reaction (perhaps tables of figures, or graphs showing the different parameters of the reaction) is very different from the interface the same person would use if they were wanting to see the flow of a chemical around the whole site. This would probably be in the form of a diagrammatic representation of the site. The circumstances under which the interface is to operate are also important. In the last chapter mention was made of the nurse looking after a group of patients. In those circumstances an audible warning that a problem may be occurring is far more sensible than a visual one which may be ignored if the nurse’s attention is drawn away from the screen. Finally, the designer of the interface needs to take account of the purpose for which the interface was designed, namely the transfer of data into the system and the communication of information from the system to the user. If the user is using the computer to play a game then the paramount importance of the interface is that it adds to the enjoyment of the user.
Consideration of the purpose of the interface,
· who it is for
· what information needs to be conveyed
· the circumstances under which the interface must operate
· the effectiveness of the communication
· the enjoyment obtained from using it
are all important when the interface is being designed.
1.10 (b) Peripheral Hardware for a Given Application
This section deals with the needs of the application rather than the peripheral devices themselves. For details of the devices the reader’s attention is drawn to chapter 1.5.
When peripheral devices are chosen a number of factors need to be taken into account.
· Who are the people that are going to use the application? Specifically, consideration must be given to their age (can they read is an obvious question), their ability with computer systems, their understanding of the software in use (do they need to be given instruction about how to use it or do they know what is expected of them?), any physical disabilities which may make some hardware impossible to use.
· Is the system automated in any way? If so the peripherals may include sensors and actuators.
· Under what circumstances will the system be used? If the input and output devices are to be used in the open air then the environment will dictate some restrictions which would not be necessary if the system was being used in a computer room.
· The software that is being used. The software will dictate the type of input required and the type of output that will be produced, consequently it will also have an influence on the peripherals that are suitable for that input and output.
1.10 (c) HCI Design Issues
Short term and Long term memory
The information produced by a system can be of such a large volume that it is not possible for all the information to be stored for future use by the user. Some of the information is presented via the user computer interface, perhaps in the form of a scrolling graph. Such data is very transitory in nature because the screen display is being constantly updated. Such data is part of the short term memory. The long term memory is that which stores the data for future reference.
Visual perception
This includes all the information that is presented by the system in such a way that it can be seen with the eyes. This means that the information will be presented on a screen or on a hardcopy produced by a printer. The size of individual pieces of information will be important as will the contrast used and the type of font in the case of text.
Colour
Colour is an important part of any HCI. The contrasting use of colours can highlight the more important information, or can be used to distinguish one type of information from another. The different levels of contrast between colours are necessary if the individual items of information are to stand out. Black on white provides the highest possible contrast, while dark blue on black is very difficult to decipher.
Layout
The layout of the data on the screen is important. The eye naturally reads from left to right and from top to bottom. This means that more important information should be positioned toward the top and left of the screen. The volume of information on the screen at any one time is also important because there is a limit to the amount that the eye can follow and the brain distinguish in one sweep of the screen content. If the information should be seen in an order, then the correct screen order is from top left to bottom right corners, as the eye naturally reads.
Content
The content of the information presented is important because a user will soon begin to ignore items of information that are constantly being put on the screen despite not being necessary. Similarly, if a method is used to show that a piece of information needs urgent attention, while the operator does not perceive the urgency, then all such highlighted information may be begun to be ignored in the same way.
1.10 (f) Speed Mismatch
A typical computer system will consist of the processor to do the necessary calculations or other processing, the peripheral devices to allow input, output and storage of data/information, and the human being that is using the computer.
The processor can carry out its side of the task at great speed while the human being is very slow, both at providing input and making sense of the output. This difference in speed is known as the speed mismatch between the operator and the processor. Peripheral devices work at far greater speeds than the human being, but are considerably slower than the processor, consequently there are also speed mismatches on both types of communication concerning peripherals. If there are enough computer systems this speed mismatch does not matter so much, but if there is a shortage of processing time, then a method needs to be found to keep the slowest parts of the systems isolated from the processor. One way of doing this is to use batch processing (see section 2).
The speed mismatch causes more problems if the decisions of the computer need to be acted upon immediately. If a computer is being used to control the insertion of the graphite rods into a nuclear reactor it may become important to ignore the human being once the decision has been made and simply to report that an action has been taken after the event. In this way the speed mismatch has been overcome by cutting out the slowest part of the system.
Example Questions
A company has a workforce of around 2000. Some work in the office using the computer system for administrative tasks, while others use the computer system on the production line for giving details of orders that need to be manufactured.
1. Describe the factors that would have been important in the design of the software interfaces to be used by the office workers and the shop floor workers. (6)
2. Select appropriate peripheral hardware for these two application areas, giving reasons for your choices. (12)
3. The office workers often have to key in the details of new members of the workforce. The details of the worker are on a standard form which the new employee fills in. Explain how a form based software interface would be useful to the worker who has to key in the data. (4)
4. Explain the types of output that would be expected from the computer on the factory production line, if it is used to control the speed of the production line as well as being used as a tool for the workers. (4)
5. Explain why speed mismatch would mean that the computer should be in control of the speed of the production line. (3)
Chapter 1.9 Handling of Data in Information Systems
Chapter 1.9 Handling of Data in Information Systems
1.9 (a) Manual and Automatic methods of Data Entry
All computer systems need to have data input to them otherwise they have nothing to process. The methods of collecting the data can be divided into two types: automatic and manual data collection.
Automatic Data Collection
The input devices used here are:
OMR: for multiple choice answer sheet marking
OCR: for scanning of documents that can be modified
MICR: for clearing bank cheques
Sensors: Here data will be captured in analogue form. Hence, there is a need for an Analogue-to Digital Converter to convert the data in digital form before sending to the computer.
1.9 (b) Methods of Image Capture
Scanner:
Used to convert printed text or graphics into digital form.
Video capture card
A video picture is made up of a series of images which are changed approximately 26 times per second in order to fool the brain into thinking that the images are moving. A video capture card is an interface board which fits into one of the expansion slots in a processor that allows the processor to store the values of the screen pixels for a specific picture. In other words it allows the action to be frozen. A typical example of the use of a video capture card is the market stall that uses a video camera to take an image of a customer and then to select one image to print onto a T shirt.
Digital camera
Works in a similar way to an optical camera but does not store the image on film. Instead, the image is stored electronically enabling the user to download it into a computer and manipulate the image and print out the images if desired.
Each of these image capture systems results in an electronic image being stored in the computer system. Image manipulation software can then be used to alter or edit the image in any way that is required. While this allows the user to use their imagination and to tidy up pictures or crop them to miss out unwanted parts of the image, it also allows unscrupulous people to produce pictures with very little foundation in reality. It used to be said that: “The camera never lies”, this is certainly no longer true, witness the film Forrest Gump.
1.9 (c) Validation and Verification
Verification
Verification means checking the input data with the original data to make sure that there have been no transcription errors. The standard way to do this is to input the data twice to the computer system. The computer then checks the two sets of data (which should be the same) and if there is a difference between the two sets of data the computer knows that one of the inputs is wrong. It won’t know which on is wrong but it can now ask the operator to check that particular input.
Validation
The first thing is to dispel a common misinterpretation of validation. In section 1.6.f checking of data was mentioned. Specifically, the use of parity bits to check data. This is NOT validation. Parity bits and echoing back are techniques that are used to check that data has been transmitted properly within a computer system (e.g. from the disk drive to the processor), validation checks are used to check the input of data to the system in the first place.
Validation is a check on DATA INPUT to the system by comparing the data input with a set of rules that the computer has been told the data must follow. If the data does not match up with the rules then there must be an error. There are many different types of validation check that can be used to check input in different applications.
1. Range check. A mathematics exam is out of 100. A simple validation rule that the computer can apply to any data that is input is that the mark must be between 0 and 100 inclusive. Consequently, a mark of 101 would be rejected by this check as being outside the acceptable range.
2. Character check. A person’s name will consist of letters of the alphabet and sometimes a hyphen or apostrophe. This rule can be applied to input of a person’s name so that dav2d will immediately be rejected as unacceptable.
3. Format check. A particular application is set up to accept a national insurance number. Each person has a unique national insurance number, but they all have the same format of characters, 2 letters followed by 6 digits followed by a single letter. If the computer knows this rule then it knows what the format of a NI number is and would reject ABC12345Z because it is in the wrong format, it breaks the rule.
4. Length check. A NI number has 9 characters, if more or fewer than 9 characters are keyed in then the data cannot be accurate.
5. Existence check. A bar code is read at a supermarket check out till. The code is sent to the main computer which will search for that code on the stock file. As the stock file contains details of all items held in stock, if it is not there then the item cannot exist, which it obviously does, therefore the code must have been wrongly read.
6. Check digit. When the code is read on the item at the supermarket, it consists of numbers. One number is special, it is called the check digit. If the other numbers have some arithmetic done to them using a simple algorithm the answer should be this special digit. When the code is read at the check out till, if the arithmetic does not give the check digit it must have been read wrongly, it is at this point that the beeping sound would normally be heard if everything is alright.
1.9 (d) Output Formats
When data has been processed by a computer system it is necessary to report the results of the processing. There are a number of different ways that the results can be reported to the user.
Graphs
Graphs show trends very clearly.
Reports
A report is a hard copy printout of the values of variables. This has the advantage of producing the actual figures according to the values specified by the user. However, the figures themselves may need skill to interpret their significance and the value of figures in a vacuum is often hard to justify.
Interactive presentations
The previous forms have relied on the format of the report being decided without the luxury of being able to see what the figures look like in the first place. If the system allows the user to decide the type and range of output required during the run then there is some positive user involvement leading to an interactive presentation where the user can adjust the output to suit their needs.
Sound
Many applications do not lend themselves to a standard, visual, printout. Sound can be used for output from some systems. Obvious examples would be voice synthesis for reporting to blind people and an alarm system to protect property against burglars.
Video
Video is a visually satisfying form of output that takes large amounts of memory to produce because the nature of the medium requires large quantities of pictures to produce the feel of continuous motion. Video is useful for demonstration of techniques where there is little value in pages of instruction if a simple video can illustrate something better.
Images
‘Images’ can refer to any of the forms of output mentioned when they are shown on a monitor screen, as opposed to the hard copy produced from a printer.
Animations
Provide a good stimulus for an audience and lead from one slide to another when making a slide based presentation. Animation takes considerably less processing power than other forms of motion, unless the image being animated is complex. Animation is used so often that it can come across as being a boring technique that has just been added for ‘gloss’.
Example Questions
1. a) State two methods of data entry used by banks in their cheque system. (2)
b) Explain why banks find the use of your two examples suitable for this application.
2. A small stall is to be opened, as part of a fairground, where the customer can have their likeness printed on to the front of a sweatshirt. Describe two possible methods of capturing the image to be printed. (4)
3. A mail order firm receives orders from customers on paper order forms. These are keyed into the computer system by operators. The data that is to be keyed in includes the 5 digit article number, the name of the customer and the date that the order has been received.
a) Explain how the data input would be verified. (3)
b) Describe three different validation routines that could be performed on the data. (6)
4. A reaction vessel in a chemical plant is monitored, along with many others, by a computer system using a number of sensors of different types. Describe three different types of output that would be used by such a system, stating why such a use would be necessary. (6)
5. Explain what is meant by the timeliness and relevance of data. (2)
Chapter 1.8 Choosing Applications Software
Chapter 1.8 Choosing Applications Software
1.8 (a) Custom Written and Off-the-Shelf Software.
When the analyst has analyzed the problem and come to a conclusion about how it can be solved, a decision has to be made about the software that should be used.
There are many pieces of software that have already been written and are immediately available to buy. This type of software is called ‘off-the-shelf’ software because you can literally go into a computer shop and pick a copy off the shelf. There are a number of advantages in buying an off-the-shelf package:
· The software has already been written and so is immediately available rather than having to wait, sometimes a considerable time, for it to be written.
· The software will be used by many people or organisations, therefore they share the development costs rather than one having to foot the whole bill. This implies that the software will be considerably cheaper.
· Copies of the software have been in use for some time and will have been in use by a variety of users. This means that any bugs in the software should have been found and rectified, consequently it can be expected to work.
· If it comes as part of a suite of software it can be relied upon to be compatible with other applications, allowing, for example, the import of data.
· Because the software will be in general use there are likely to be well established training courses for the staff to be sent on to learn about the software.
A Custom package is one that has been specially written to solve a specific problem. Perhaps there is no freely available piece of software that will satisfy the needs of the company, A piece of custom software should mean that the organisation gets a piece of software that will do all the things that it requires doing, and, equally importantly, does not contain extra routines that will never be used.
1.8 (c) Generic Applications Software.
Word processing.
Used for applications that have the need to communicate with others using text. Writing letters, mail merging, preparing text documents for use in other software packages, are all typical uses of a word processing package.
Spreadsheets.
A spreadsheet is particularly useful because it can store different types of data, including numerical data, and that it can perform calculations on the areas (cells) where the numerical data is being stored.
Desktop publishing (DTP).
This type of software is characterised by the ability to produce a page of printed output that has been designed by using advanced layout techniques. The page may well contain text, graphics, tables and many other types of output each one of which may be better produced using a word processor or a drawing package or a spreadsheet. The value of the DTP is that it contains powerful tools for arranging these individual items on the page, the printout of which can be used directly as the starting point for a printing process. Typically DTP software is used for the production of leaflets, posters, proof copies of books and magazines.
Presentation software.
. The software allows for the preparation of a show which typically follows a storyboard of individual screens. The software allows morphing from one screen to another and also allows animation and full use of text and graphics within individual screens. If required, a soundtrack can be added to complement the pictures being shown.
Drawing packages.
This is a package that produces graphics output. Often such output is exported to a DTP for inclusion in some publication, or to a piece of presentation software for inclusion in a display sequence. Another use for such output is to enliven a page on the world wide web. There are many different forms of graphics package split into groups dependent on the way that the graphic is produced. The two most common are bitmap graphics where each pixel is treated separately, and vector graphics where the lines on the drawing are created mathematically. Different software packages create the graphics in different ways for instance Paintbrush creates pictures in bitmap form while Draw uses vectors. The simple way of describing the difference is in sizing the drawing. If a drawing held as a bitmap is increased in size then each of the pixels is increased in size and hence becomes more obvious. If a drawing stored using vector graphics is increased in size the only thing that changes is the mathematical formulae for producing the lines, which will produce a picture of comparable quality whatever the size.
1.8 (d) Applications for which Common Packages are not appropriate
Common applications packages are those that have been designed to satisfy particular needs that are common to a number of different applications. There are many other examples where computers are necessary but where the use is so specialised that the software will need to be written (or at least tailored) for that particular use. Uses that would require such specialist software are legion, but would include many uses of control software. Robots used on production lines tend to be one-off machines, designed for that particular purpose, consequently, the software that would drive them would, similarly, be one-off. A stock control system in a warehouse would have standard modules, but would have other sections which would be for that warehousing system alone. The important consideration is how different from the standard design is the system for which we want the software, the further away from the standard, the more difficult it is to use standard software, and the more likelihood there is that the system will require software written specially for it.
Example Questions.
1. Discuss the reasons that a solicitors’ practice would have for choosing off-the –shelf software rather than custom written software if it was decided to change the word processor currently being used because it was perceived to be out of date. (4)
2. In the same scenario, State two reasons why custom made software might be more appropriate than off-the-shelf software. (2)
3. Describe how CAD/CAM can be used to produce prototype designs in a manufacturing process. (4)
4. A firm produces widgets for sale to the brewing industry.
A brewing company may come to the firm with a proposal for a widget to fit a particular container which will need to be produced by the firm which will then ship the finished product in batches and invoice the brewing company. Sometimes the sales team will be sent to try to persuade the brewing firm of the advantages of the company’s widgets.
Explain how the company can use commonly available software in the running of its business. (6)
Chapter 1.7 Systems Development Life Cycle
Chapter 1.7 Systems Development Life Cycle.
1.7 (a) System Lifecycle as an Iterative Process
When considering the systems development life cycle it is important to think of the different stages as a continually developing process rather than each stage being an end in itself.
When one of the stages is completed the following stages may mean that the previous ones may need to be considered again. If the problem definition agreed with the end user later proves to be impossible to implement then the problem will have to be redefined. If the required input proves to be not feasible then it may be necessary to alter the expected output. If, during the training of the staff, one of the input operators proves to be colour blind then the input screens may need to be altered in order to not have any clashes between red and green.
This reliance of each stage being on the following stages as well as the previous ones means that the process is said to be iterative.
1.7 (b) Problem Definition
It is important from the outset to ensure that when a computer system is being designed all those that are involved are agreed about the aims of the system.
There will normally be a person, or a company or organisation that decides that a task would benefit from computerisation. This belief normally arises because there is a problem which cannot be solved by previously used methods or similar problems seem to have been solved by computerisation elsewhere. Unfortunately, the owner of the problem probably understands the problem itself quite well, but does not understand the consequences of using computers to try to solve the problem, or, indeed, whether such a solution is even possible. For this reason it is necessary for the organisation to employ a specialist who does understand computers and computerised solutions to problems. This is the systems analyst. Unfortunately, it is probable that the systems analyst is not expert in the area of the problem.
The system analyst’s job is to solve the problem by planning and overseeing the introduction of computer technologies. The owner of the problem will be happy if the analyst can introduce a computer solution. The problem arises when the analyst, who doesn’t know very much about the business, solves the problem that they think needs solving, while the owner of the problem expects a very different problem to be solved.
The definition of the problem is the most important part of the analysis because if it is not done correctly the wrong problem may be solved.
1.7 (c) A Feasibility Study.
When the organisation and the systems analyst have agreed the definition of the problem, a decision must be made about the value of continuing to develop the computerised solution. The organisation may be convinced that there is a problem to be solved, and that its solution will be worth the effort and the expense. However, the systems analyst is being paid to look at the problem, and its solution, from another point of view. The analyst is an expert in computer systems and what is possible with computer systems. This analyst must consider the problem from the point of view of the computerised part of the solution and make a report to the organisation saying whether the solution is possible and sensible. This report is called the feasibility study because it says whether the solution is feasible.
The feasibility study will consider the problem, and the proposed solution, from a number of points of view.
· Is the solution technically possible? A car firm may decide that if robots are used on the production line to assemble the different parts of engines then quality of work may improve. However, if it is not possible to manufacture a robot arm of the correct dimensions to fit into the small areas under a car bonnet, it doesn’t matter how big an improvement there would be in the quality of the finished product, it would simply not be feasible
.
· Is the solution economic to produce? Perhaps the robots exist that can be programmed to assemble this engine and the benefits will be worthwhile. However, if the cost of the robots and the program to control them is so great that it puts the car manufacturer out of business, the introduction of the robots is not feasible.
· Is the solution economic to run? It has been decided that there are tremendous benefits in producing a robot production line and the robots are very cheap to buy, but they have so many electric motors, and they are so slow at assembling the engines that it is cheaper to employ people to do the job.
· What is the effect on the human beings involved? If the car plant is the only major employer in the region, and the introduction will put much of the workforce out of work, then the employer may decide that the human cost is too great, certainly the Government would.
· Is the workforce skilled enough? It will be necessary to employ highly skilled technicians to look after the robots. If there are no workers with the necessary skills then the computerisation is not feasible.
· What effect will there be on the customer? If the customer is likely to be impressed with the introduction of the new systems then it may be worth the expense, however, if the customer will notice no difference, what is the point?
· Will the introduction of the new systems be economically beneficial? Put bluntly, will the introduction of robots increase the profits made by the firm?
If the feasibility study shows a positive result which is accepted by the company, the next stage will be for the analyst to collect as much information about the process as possible.
1.7 (d) Information Requirements of a System and Fact Finding
There are three accepted methods of finding out people’s views:
1. By interview. Interviews are particularly important because they allow the interviewee to talk at length, and also to leave a prepared script. However, they are very time consuming and consequently restricting in the number of people whose views can be sought.
2. By using questionnaires. Questionnaires make it possible to find out the views of a large number of people very quickly, but because the questions are pre-determined the person who is supplying the answers may find difficulty in putting their point of view across.
3. A compromise is to hold a group meeting. This allows a number of people to discuss points and make their views known and yet cuts down on the amount of time spent in interviews getting the same answers over and over again. The problem with meetings is that one or two people tend to dominate, not allowing all the members of the group to give their opinions.
1.7 (e) Requirements Specifications
The planning of any system design must start by deciding what the requirements are of the system. A system may need to store data for future reference or processing. However, simply being aware that the system may need to store data is not enough.
· Decisions need to be made about the types of data to be held as this will dictate the form that the data will be stored in and the amount of storage space required for each set of information.
· Calculations as to the number of sets of data that are going to be held have to be made because the volume of storage will make some storage devices more sensible than others. Also, the volume of storage can affect the structures that will be used to store the data.
· Decisions need to be made about the relative importance of the different ways of accessing the data. Is it going to be necessary to access individual items of data or will all the data be accessed at the same time?
· Will the data be changed regularly or is it fairly static?
1.7 (f) Data structures, Input/Output, Processing
Input Design
All systems require input. The way that the data is input to the system depends on a number of factors.
· The data that is required. Is it graphical/textual/physical in nature? Is the data already in existence or does it need to be collected first?
· The hardware that is available. Is the data to be entered via a keyboard by an operator, or is there an automatic way to enter the data?
· The experience of the operator.
· The design of the user interface.
Output Design.
The results that are produced by the system must be presented in a way that is appropriate for the application. If the system is designed to produce bank statements for customers, then it would not be sensible to have an audio output. Similarly, a burglar alarm system would not serve the purpose for which it had been designed if the output is a message on a computer screen saying that someone has broken in as there is probably no-one in the house to read it, which is why the alarm was needed in the first place.
The decision about the type of output will depend greatly upon the same factors as the input, namely, the hardware available, the form that the output needs to be in, the experience of the operator, indeed, whether there will be an operator present.
Equally important to giving enough information, is the danger of providing too much. In order for users to be able to understand the information presented various tricks can be used.
· Information can be arranged on a monitor screen by always putting the same sort of information in the same place. The operator will then quickly become accustomed to the relative importance of different areas of the screen.
· Information can be colour coded. Important information may appear in red while that which is less important is in black
· Video reversal can be used to highlight a particular piece of information effectively. This is when the normal writing on the screen is black on a white background, but the piece that needs to stand out is shown as white on a black background.
· Very important pieces of information may be shown as a dialogue box obscuring the rest of the screen until it is dealt with.
· A printer may be reserved for special messages so that a hard copy of the information is preserved. Again, the fact that the information appears on that printer means that it has a particular importance.
· Information can be made to flash, or can be printed in a different size, anything that makes the operator’s eye go to that part of the screen.
Jackson diagrams:
A Jackson diagram starts with the original problem as the highest level. The next, and subsequent, levels show how the problems in the previous levels are split up to form smaller, more manageable, problems. This continues until each of the blocks in the lowest levels are self contained, easily solvable problems. These individual problems can then be solved and combined according to the links that have been used. If the links between the different blocks are then used correctly, the result will be a solution to the original problem. Imagine a Jackson diagram as a method for showing the individual modules that go to make up a solution to a problem and the relationships between them.
An example of a Jackson diagram to show the solution to a simple problem.
A register is taken of the 25 students in a class. Each student can be either present or absent. It is necessary to print out the number of students who are present and the number absent.
Data flow diagrams:
These are diagrams that are used to describe systems. Boxes are used to stand for input, processes, storage, and output. Arrows show the direction of communication around the system, and communications outside the system. As the name implies, these diagrams are used to show the directions of flow of data from one part of a system to another. Data flow diagrams can have complex shapes for the boxes that are used, but the important thing is not the shapes of the boxes, rather the logical train of thought that has been used to produce the diagram. Rectangular boxes, though not always used, are perfectly acceptable for all elements in a data flow diagram. Such diagrams are intended to show how the processes and the data interrelate, not the details of any of the programming logic.
At this stage the analyst will also identify the hardware that will be necessary for the system to operate as the user requires, and the software characteristics that will need to be satisfied for the system to operate.
1.7 (g) System Evaluation
Any system must match certain criteria if it is to be considered successful. This does not only apply to a computer system but any system. For example, a car must satisfy various criteria before being able to be called a car
· it must move under its own power
· it must be possible to steer it
· it must have 3 or 4 wheels
· it must have seats.
1.7 (h) Documentation
The documentation of a system consists of all the text and graphics that explain how the system was produced, how it should be used, and how it can be maintained.
Documentation is created at different stages in the life of a system and for different people to use. Some of the different types of documentation are met in this section and others will be encountered later in the course. Indeed, much of the project work that is done in module 4 consists of producing the documentation for a problem solution.
Requirements specification
This is a list of the requirements of the customer for whom the system is being designed. It consists, largely, of the criteria that will be used for the evaluation of the finished system. It is usual for the system analyst and the customer to sign the list of requirements so that there is no confusion when the work is finished.
Design specification
Taking the requirements specification and working out the stages necessary to produce the required end product is known as the design specification. This will include the different stages, often shown in diagrammatic form as mentioned earlier in this chapter, and also the criteria for each stage of the solution. For example, one part of a solution may be the production of a file of data. The ways that this file of data relates to the other parts of the system, and the specification of the file (what is the key field? How many records will there be? What type of medium should it be stored on?) make up the design specification.
Program specifications
These will include detailed algorithms showing the method of solution for some of the parts of the problem. These algorithms may well be in the form of flow diagrams or pseudo code. The language to be used, the data structures necessary, and details of any library routines to be used will also be in the program specification.
Technical documentation
The technical documentation will include the program specifications, the coded program itself, details of hardware configurations. Generally, anything that will aid a technician in maintaining or updating a system. Indeed, technical documentation is otherwise known as maintenance documentation. This type of documentation is not intended to be accessible to the user of the system, who does not need any of these details to be able to use the system correctly.
User documentation
This is the documentation for the person who will actually be using the system. It contains those details that are needed to make the system operate as it should. Items normally included in the user documentation will be
· examples of output screens
· examples of valid input
· methods of input of data
· error messages and what to do when they appear
· How to install the system onto specific hardware
Some user documentation is part of the software and can be called up onto the screen when it is needed. This type of documentation is called on-screen help.
1.7 (i) Testing and Implementation Planning
When the system has been completed it has to be implemented so that it is performing the tasks for which it was designed. Initially, this involves
· ensuring that the correct hardware is available
· arranging for staff to be trained in the use of the new system
· inputting the data to the data files, either manually or by downloading them from the original system.
The system handover, itself can be done in a number of ways:
· Parallel running. Until the system can be considered fault free, the old and new systems are run side by side, both doing the same processing. This allows results to be compared to ensure that there is no problem with the new system. Such a system is ‘safe’ and also allows staff training to be carried out, but it is obviously very expensive because of the need to do everything twice. Parallel running is used in situations where the data is so valuable that there must be no possibility of failure.
· Pilot running. Key parts of the new system are run alongside the old system until it is considered that they have been fully tested. This is a compromise with the idea of parallel running, but it does not give a clear idea of the effects on the system of the large amounts of data that are going to be encountered in the full application.
· Big bang, or direct change. The old system is removed and the new system replaces it completely and immediately.
· Phasing. Parts of a system are replaced while the remaining parts are covered by the old system. This allows for some testing of the new system to be done, and for staff training to take place, but also allows for a back-up position if the new version does not work as anticipated.
1.7 (j) System Maintenance and the Software Life Span
Adaptive Maintenance: Systems may be designed for a well defined purpose and may realise that purpose, hence they would be considered successful. However, the original reasons for a particular system to be created may change, the hardware may alter, the law governing a system may change. For many reasons the original system may no longer be satisfactory. One solution would be to produce a totally new system, another would be to adapt the present one so that it can be used in the new circumstances. This situation is reviewing the system and is the main reason for technical documentation.
Corrective Maintenance: While the system is running it will need attention because of faults being discovered, this again needs a technician with a set of maintenance documentation.
