7 Unit summary

7.1 What have you learnt in this unit?

This unit began by exploring some basic issues involving computers:

• the nature of data and information;
  
• why human beings need (and want) computers;
  
• the prevalence of computers in modern life.
  

The unit looked briefly at how a computer-based society affects the average person who (whether he or she knows it or not) has a persona that consists of data about them held by many diverse organisations.
Much of this unit consisted of case studies illustrating the possibilities for computer use. They raised some of the issues posed by computing technologies, such as:

• the distinction between data and information;
  
• what computers can do with data to produce information;
  
• how computers can be used to work with data and search for it, control machines, and support commercial operations.
  

There are a number of themes running through this unit.

• Data requires encoding.
  
• In order to function, a computer requires data which may be stored in databases.
  
• Data has to be transmitted from place to place.
  
• At the heart of a computer system there are one or more programs.
  
• Many current computer systems are distributed, in that they consist of a number of computers which cooperate and communicate with each other in order to function.
  
• Information has to be fit-for-purpose.
  
• Security and trustworthiness are major concerns with many systems.
  
• Computer systems also have drawbacks and adverse effects. They also have social, political, legal and ethical implications.
  

You should be able to define the following terms in your own words.

case study	hit
computer	information
computer program	internet
computer system	keyword
data	parameter
database	perceptual data
database server	search engine
distributed system	sensation
gateway	sign/symbol
global positioning system (GPS)	World Wide Web (the web)

6.3 Summary

This section examined how computers can be used to control machines. It used the household washing machine as a case study and explored how the microcomputer contained in such a machine is programmed to:

• provide an interface for the user to operate the machine;
  
• control the way the machine carries out the operations chosen by the user.
  

The washing machine case study also illustrated the necessity of building safety features into computer-controlled mechanisms.
Computers are also used to support selling goods and services via the web. A case study of a successful company showed what the information requirements for such a system are, and examined how two or more computers can cooperate as part of a distributed system to satisfy these requirements in a way that is secure.

6.2.3 Security: are my credit card details safe?

Many people now shop regularly on the web. However, many others don't because they fear that an unscrupulous person could obtain their credit card details. They also fear that if they provide their names and addresses to a firm on the web, they will be bombarded with junk mail (or its electronic equivalent, junk email). Some worry that, since anyone can put up a website, the seller may be bogus and no goods will appear after the sale has been completed or won't be as advertised.
Consequently, other important issues raised by this case study are security and trustworthiness. The internet is a remarkably open medium. It does not take too much effort to ‘capture’ the data that flows along communication lines. Someone could theoretically read your credit card details as they are transmitted between your computer and that of the seller. (I use the term ‘theoretically’ because there exist techniques which enable the data to be transformed into a form which would be virtually impossible to read.)
You can be reasonably confident of buying from a website if it displays one of two things.

1. The address shown in the bar at the top of the screen should start with ‘https’ instead of ‘http’. The letter ‘s’ means you are connected to a secure web server using techniques to protect your details from electronic snoopers.
   
2. An icon representing a small key is present. This also indicates that the web server you are connected to is a secure one.
   

Another safety precaution is to deal only with web sellers you know are reputable. Consumer organisations often have schemes for accrediting web sellers who are legitimate and secure dealers. Friends and neighbours may also be able to recommend reputable and secure web sellers.

SAQ 9

Is web selling, as practised by a firm like Lakeland, an example of a distributed system? Explain.

Answer

Yes, it is a distributed system. It consists of user PCs, web servers, and database servers, with data and information being transferred between them using networks (in this case the internet).

6.2.2 Database servers

To be able to search a website like Lakeland's requires not only a web server but a database server. Like a web server, a database server is a computer that responds to requests from other computers. Its task is to find and extract data from a database.
The web and database servers form part of a distributed system. This means that separate computers exchange data and information across a network (in this case the internet) to produce results for a user. For example, suppose I use the keyword search to ask for ‘kitchen cleaners’. This request is transferred to the web server, which has an index of products which can be categorised as kitchen cleaners. It then sends these product numbers to the database server, which locates the correct items in the product database and returns information about them (pictures, description and price) via the web server to my browser.
Compared with the simple data from which the complex DNA database is built, the data processed by the database servers at a company like Lakeland is complex (text, graphics, pictures).

6.2.1 Using a sales website

A visitor to a sales website is usually able to:

• browse through the details of the goods for sale;
  
• search for a particular product;
  
• check on the availability of goods;
  
• read reviews of the products by other purchasers;
  
• register to receive newsletters which detail new items of interest;
  
• buy products using credit or debit cards, and in some cases, other payment methods such as cheques.
  

6.2 Selling on the weba

The web is fast becoming a medium for selling everything from books to clothes, gardening tools to beauty products, investment advice to travel services. Web-based selling seems to be concentrated in three main categories of company:

• existing catalogue sales companies which have put their catalogues online to allow customers to buy using the web;
  
• existing companies whose products are largely information and which have used the web as a means of providing a personalised service or one with a very quick response;
  
• companies which have started from scratch using the web as their only sales medium.
  

6.1.4 Controlling the machine

The major task of a washing machine microcomputer is to control the actions of the machine in accordance with the wash programme selected. To do this, the computer is electrically attached to a variety of:

• actuators that cause mechanical parts of the system to work;
  
• sensors that sense the state of some aspect of the machine, such as water temperature.
  

There is an actuator to open or close the water input valve. Another controls the turning of the drum, and another the pumping of water through the machine. There is also one for pumping the water to the drain and one for controlling the water that washes through the tray holding washing powder and fabric softener. Lastly, there is an actuator that turns on a heating coil if the water temperature is below the desired temperature for the wash.
As regards sensors, my machine has one to check water level, and another to check water temperature. It also has a sensor that weighs the dry laundry at the start of the cycle, providing data that the microcomputer program uses to determine how much water to use for each wash. This enables my machine to optimise water use, and hence conserve resources (water and the electricity to heat the water).

6.1.3 Ensuring safety

Ensuring that a user can't choose a wash temperature that's too hot for the ‘hand wash’ programme is an example of ensuring safety. In other words, the washing machine microcomputer is trying to prevent the user making choices that are not sensible. Of course, I could put a load of delicate washing in and choose the ‘cotton’ programme which has a temperature of 90°C. The computer program controlling the machine has no way of knowing that I've put silks or woollens in and not cottons. The worst that would happen, however, is that I would ruin some expensive clothing due to my own negligence.
What about the safety of the user? A washing machine could be dangerous if anyone could put their hand into the drum when it was moving, or when the water was very hot (anything over 40°C can scald), or when the water level is high enough to spill out of the door. The programme on my machine does allow the user to open the door to insert additional items during the cycle, but only when safety conditions are met (drum not moving, water not too hot, water not too high). It is incumbent on the designer of any such system to ensure that basic safety requirements are met. While it may not result in serious harm if, for example, one can open the door when water is above the level of the bottom of the door, customer satisfaction would surely plummet were this to happen.
Some computer-controlled applications (e.g. controlling a flying aircraft) have to go further towards ensuring that an operator doesn't jeopardise situations due to negligence. These are not discussed in this unit, but you should be aware that they exist. They are called safety-critical systems, which means that serious harm or loss of life could occur if these systems break down, or do not function properly.

Exercise 15

It is common in modern cars to have central locking. This usually involves pressing a button on a key fob and sending a signal to the car from a short distance which locks or unlocks all doors simultaneously. A button on the control panel may work in a similar way to lock and unlock all the doors from inside.

1. Can you identify any safety situations that would affect the lock-control program in the car's microcomputer?
   
2. What kind of information might a driver need about the door locks?
   

   Discussion

   1. It might be dangerous to allow someone to unlock the doors while the car is in motion. For example, a child might press the button on the control panel, unlocking the doors, then accidentally open the door and fall out. With very small children, it might be dangerous for the child to be able to unlock any door (even when the car is stationary) without the driver knowing. Thus one safety consideration might be to ensure that it is not possible to override child-proof locks accidentally or through carelessness.
      
   2. The driver might simply need a light to tell him or her whether the locks were engaged or not.
      
   
   

6.1.2 Choosing programmes and parameters

Another part of the interface shown in Figure 15 allows the user to select one from a variety of predetermined washing programmes, and to change some of the parameters. If I choose the ‘cotton’ programme, for example, the microcomputer's program assumes that I wish to wash this load of laundry at 60°C, use the main wash programme, and spin the washing at the highest speed. Sometimes this programme is fine, but at other times I may want to select the higher temperature of 90°C in order, say, to sterilise the laundry (e.g. nappies), or a lower temperature (e.g. to prevent dark colours fading).
I may also select the pre-wash if my laundry is especially dirty or the additional rinse if a member of the family has sensitive skin which may react to residues of washing powder.
Finally, the microcomputer's program ensures I don't do anything silly. For example, if I select the ‘hand wash’ programme, it will not allow me to change the temperature to one higher than the pre-programmed 30°C.

Exercise 14

What kind of interface would you expect on a very simple microwave oven (one without predetermined programmes)?

Discussion

Since power level (e.g. defrost, low, medium and high) and time are important when microwaving food, the user needs to be able to select these two parameters.
Typically, a microwave interface will have buttons or a dial for selecting the power level, and a numeric keypad or dial for setting the time in terms of minutes and seconds. The display might indicate the power level chosen, and will certainly show the time remaining.
The interface will also have two other important controls: a ‘Start’ button and an ‘Open door’ button.
You may have said something a bit different, depending on your familiarity with microwave ovens.

6 Controlling things; selling things

6.1 Controlling things

As you learned in Section 1, computers can collect, process, store and distribute information. This section shows that they can also be used to:

• control machines and simple mechanisms;
  
• conduct a special kind of commerce: selling on the web.
  

Let us examine more closely that common household appliance, the automatic washing machine. Virtually all such machines sold in the last decade or so are controlled using a microcomputer of some type. Before that, such control was provided by mechanical systems. However, because these had moving parts they suffered from wear, and tended to break down frequently or require replacement. Also, the nature of mechanical control systems limited how complex they could be. Consequently, they tended to be quite simple, and therefore less ‘automatic’.
The main tasks of a microcomputer in a modern washing machine are to:

• present an interface to the users that lets them know what possibilities there are and what the current state of the machine is;
  
• allow the user to select one from a variety of predetermined washing programmes;
  
• change some of the parameters (such as water temperature) to suit particular conditions;
  
• initiate, control and finally halt the actions of the machine in accordance with the wash programme selected;
  
• in some machines, ensure that the washing is done efficiently with minimum inputs of water or washing powder, in the interests of reducing resource use and maximising environmental protection;
  
• ensure safe operation of the machine.
  

Let's examine some of these tasks in more detail.

5.3 Summary

This section made an interesting contrast between simple data that generates large and complex structures that require large and complex programs to handle them, and complex data which a complex but easy to use program helps a non-expert handle in some interesting, creative, flexible ways.
The case study on DNA illustrated how simple data (consisting of only four elements) can be combined into very large and complex structures (genes and chromosomes). You learned how such large and complex structures, when stored in databases, present certain computational problems. The difficulty of finding anything in such large databases where data may be very repetitive or partial, or its location not known means that huge computational effort is required, both to build the database in the first place, and then to use it effectively.
In contrast, the second case study examined how complex data, such as the graphical representation of a scene, can be made relatively easy to use by a non-expert. The case study showed how the flexibility of a computer and its ability to make and store multiple copies provides great scope for creativity.

5.2.1 Transforming the natural to the designed

The artist Christine Martell lives in Oregon in the United States and works with beads and visual images. I asked her to describe how she makes use of a computer to create her visual images of flowers and trees. She writes of her work:

I start by finding flowers that are compelling in some way, most often in form and colour. I take photographs with a 35 mm camera having a macro lens.
I'm usually looking for a line that might suggest movement or gesture. I find a place that might be the resting place in the movement, and focus the camera there. Often times the background is out of the focal range.
When I have the film developed, I choose a lab that tends to make the photographs saturated [with little or no admixture of white] and rich. I prefer to bring the colour ‘down’ electronically rather than try to enhance it. I have the prints made in 5 by 7 inch size.
I scan the photograph into the computer, using a simple consumer grade scanner. I copy the image to make a working copy. I keep the original photo scan as a separate file, so I can move back and forth between the images to restore original edges and details.
When I draw into the images electronically using a drawing tablet, I am usually looking to create a dynamic energy; to express a movement and visually emphasise the contrast between that energy and the stillness of the flower. I draw back into the images with my digitising tablet, using Painter software. I hardly ever use filters [standard effects made available by ‘painting’ software, equivalent to using a lens filter on a conventional camera] as the effect is too uniform for my taste. Once in a while, if I need a uniform texture for a background, I'll use a filter… or I might start with a filtered texture, then draw into it.
The computer gives me the freedom to mix the visual effects of media that would not readily combine in traditional media. I also can work through many more ideas electronically.

5.2 Art and the common computer

Art is difficult to define. But all art involves the Exercise of human skill. A natural object, such as a piece of driftwood, a flower, a bird song, can move us to admire it as beautiful or intriguing or comforting, but it isn't art. Artists (be they photographers, painters, sculptors, actors, musicians, authors or dancers) use their skill to transform natural objects, materials or signs (paint, clay, their own body or voice, the sounds of musical instrument, words) into something else: something with value in its own right rather than for the way in which it might be used.
And what, you may ask, do computers have to do with art?
Central to this unit is the idea that a computer is essentially a tool. And because of the flexibility of programming, it is an exceedingly flexible tool. With the right sort of program and appropriate peripheral devices, a computer can be used by artists to produce art. This subsection will examine how computers can be used to produce visual art.
If you examine a photograph, a painting or a view out of your window carefully, you will notice that what you are looking at is, for the most part, incredibly complex. Colours vary across an almost infinite colour spectrum. There are apparent lines or edges, and objects within the view will be clearly or fuzzily defined depending upon lighting conditions and distance from the person viewing the scene.

Screening for genetic defects

Now that scientists have mapped the human genome, computers can be used to detect genetic defects.
Screening for genetic diseases existed before the application of computers. Family histories were used, together with a knowledge of inheritance patterns and statistics, to determine the likelihood of a couple having offspring with genetic disorders such as sickle cell anaemia.
Some genetic disorders such as phenylketonuria have had simple chemical detection tests available for some time. Once detected, careful control of diet prevents mental retardation, demonstrating the value of detecting the presence of a genetic disease before any symptoms have appeared.
What the computer adds to the screening process is the power to compare very long genetic sequences (i.e. sequences of base pairs) against the human genome in a way that would be far too time consuming (and therefore expensive) to be carried out by hand. Once a particular gene and type of defect has been identified, it becomes possible to develop a test to find out whether a patient has that genetic defect well before any signs of it appear.
Genetic tests are used for several reasons, including:

5.1.2 The human genome

All life is ‘encoded’ chemically in genes. What this means is that the structure of an organism, the organs it possesses, its colouring, and so on are all determined by different genes. A very simple organism may have just a few genes, and a complex one tens of thousands. The ‘map’ of an organism's genes is referred to as its genome. It shows, in essence, which genes give rise to which characteristics or traits of the organism. The word ‘template’ would describe the genome better than ‘map’.
Figure 13 shows the 23 pairs of human chromosomes that constitute the structure of the human genome. These chromosomes contain between 30,000 and 40,000 genes in total. For each human characteristic, such as eye or hair colour, the human genome shows where the genes are that control that characteristic.

5.1.1 What is DNA?

DNA (deoxyribonucleic acid) is frequently in the news for four main reasons.

1. DNA can be used in crime detection to eliminate innocent suspects from enquiries or, conversely, to identify with a very high degree of probability the guilty.
   
2. DNA is now used in medicine to detect the possibility that diseases having a genetic origin may occur in an individual. This enables doctors to prescribe preventative treatments.
   
3. It is hoped that discoveries about DNA will yield important new treatments for hitherto intractable diseases and conditions.
   
4. DNA can be used to identify victims of disasters, and establish whether people are related.
   

5 Computers as tools for working with data

5.1 Genetic databases and disease

Section 2 looked at data and information from two different perspectives: that of the individual and that of commercial organisation. The type of data you have will dictate both why you want to process it using a computer and, to a large extent, how that is done.
This section contains two short case studies whose unifying theme is that the computer and its programs are tools for working with data. The two studies provide an interesting contrast between:

• simple data in large and complex structures (which require large and complex programs to handle them), and
  
• complex data which a complex program helps a non-expert to handle in some interesting, creative, flexible ways.
  

This subsection uses a case study to show how simple data (the four bases in DNA) can be combined in different ways to create a huge and complex collection of information.

4.4 Summary

This section described how computers can be used in geographical applications (and in doing so it discussed maps and showed how modern maps are composed of layers of different data).
It discussed the GPS to demonstrate how computers can communicate in order to solve a problem, such as navigation.
It also showed how the geographical data that supports both map-making and the GPS navigation system can be presented in different forms such as a map, a list of directions, a moving graphical display on a navigation device such as a GPS receiver or as spoken directions. The reasons why one form of presentation is preferable over another were discussed: it depends on fitness-for-purpose, i.e. on the requirements of the user and/or the situation in which the information is needed.
Finally the section described how computers can be used to find information on the web. The two activities associated with this section introduced you to gateways and to the simple and advanced use of search engines.

4.2.3 Using a search engine more effectively

The search shown in Figure 9(b) is an example of how to use a search engine in a simple way. However, one of the problems with finding information on the web is that there is so much! And not all of it is relevant to what you want. My search for ‘rugby’ and ‘wales’ using the Google search engine yielded about 420,000 results or ‘hits’ (see the information contained in the blue strip on Figure 9(b)). The first few sites listed will probably tell me what I want to know. But what about all the others? Are they all about the game of rugby in Wales?
The answer is ‘no’. A website about rugby in New South Wales, Australia also appeared as a result of this search. Google didn't make a mistake since the site contains the chosen keywords. However, it wasn't smart enough to distinguish between Wales and New South Wales.
If you are just looking (‘surfing’) for information in a general way, too much information isn't always a problem. Where it becomes irritating and counterproductive is when you are looking for some quite specific information.

Example 4

Suppose you're interested in genealogy, and your surname is Bird. If you search on the web by typing in the keywords ‘bird’ and ‘family’, the web server will return every website it finds with those two words in it, so you'll probably find scientific and hobby sites on bird ‘families’ such as the passerines! It's clearly not what you want, but do you need to examine all the websites returned (which could run into hundreds) to find the one you're looking for?
The answer is that there are ‘tricks’ that you can use to narrow down your search to eliminate at least some of the things you aren't looking for. Each search engine has its own ‘tricks’, though the concepts of making more targeted searches are common to most search engines. Search engine screens will generally have a selectable topic called something like ‘Advanced Search’ or ‘Search Tips’.

One obvious trick is to choose your keywords carefully. The more specific the keywords you choose, the more likely you are to get what you want. For example, if you want to find information on antique chairs, typing in just the keyword ‘antique’ will return all websites that use the word antique, and typing in the keyword ‘chair’ by itself will return all websites that use the word chair. But typing in both keywords will only return websites that use both words. The more keywords you add, the more targeted will be the websites returned to you. So adding ‘British’ to ‘antique’ and ‘chair’ will only return websites that have all three words in them.

4.2.2 Using the web more effectively: gateways

A gateway on the web is a website intended to direct users to other preselected websites containing information on a particular topic. It can also refer to a computer that acts as a message router on the internet
University librarians often set up gateways for particular areas of study, although they may be set up by anyone with sufficient expertise in a topic. Gateways may be fairly general, such as a gateway site for sciences, or more specific, such as a gateway for particle physics.
Professional or vocational bodies may also develop gateways useful to their members, as may hobby organisations. A well-known gateway for people interested in family history and genealogy is Cyndi's List. This is updated by volunteers who notify new links relevant to topics of interest such as seventeenth and eighteenth century ships' passenger lists, local history websites, lists of names of war veterans, and so on.