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3.1 Introduction

Figure 6
Figure 6 Digital camera displaying image; a memory card is shown alongside

Digital cameras need to represent still pictures digitally,
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2.7 Input and output considerations

So far in Section 2 I have focused on how the data is represented, or encoded, inside the weighing-scales computer. But how does it get into the computer? And how does it get out again in a form that users can recognise? These are big questions, and ones that later parts of the course will be going into in some detail. But I can sketch some answers here.

Weight is the most important input in the kitchen scales. To detect a weight, sensors are placed under the scalepan. They produce an e
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2.4 Representing numbers: negative integers

In Section 2.2 I showed you how integers can be encoded if they are known to be positive, treating the integers in the kitchen scales as if they were known to be positive. However, if the user invokes the ‘add-and-weigh’ function on the scales while there is an object in the scalepan and then removes th
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2.3 Representing numbers: fractions

In the denary system, a decimal point can be used to represent fractions, as in 6.5 or 24.29. One way of encoding fractions uses an exactly analogous method in binary numbers: a ‘binary point’ is inserted.

Some examples of 8-bit binary fractions are:

  • 0.0010110

  • 110.01101

  • 0101110.1

The weightings that are applied to the bits after the binary point are, reading from left to right, 1/2, 1/4, 1
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2.2.4 Positive integers: encoding larger integers

The examples and activities in this section have looked only at 8-bit numbers. They have illustrated all of the principles of encoding positive integers as binary numbers without introducing the complication of larger numbers. But of course with 8 bits only relatively small integers can be encoded.

Activi
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16.3 Networked computers in the supermarket checkout system

All these processes are very helpful for the purposes of dealing with an individual customer's purchases. However, when computers are linked in a network, many new uses are possible.

Now, I am going to draw a different system boundary. The components of this supermarket checkout system are the checkout terminal, the network and the database server. A database server is used to make the data in databases available to other computers on the network, and therefore to users. You met
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4.2 Data for identification

I have already mentioned signatures, photographs and fingerprints as examples of the kinds of data that have been used for authenticating a person's identity. Many other types of data have been used or suggested. DNA is widely used, but mostly in criminal investigations. Iris recognition, which relies on distinctive patterns in the coloured part of the eye, is another technique. Author(s): The Open University

3.1 Tables and flat databases

Databases lie at the heart of many e-government systems, and at the heart of many other ICT systems. The local government websites you looked at in Activity 6, for instance, almost certainly used databases a great deal, as do the majority of central government sites. Away from e-government, the websites for Amazon or eBay, for example, use huge databases.

Constructing a database of any complexity requires careful thought about the way information is organised in any particular context.
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References

Eyewitness Travel Guide (1997) Amsterdam. London, Dorling Kindersley. pp. 120-1.
Götz, V. (1998) Color and Type for the Screen. Berlin, RotoVision (in collaboration with Grey Press).
Hartley, J. (1994) Designing Instructional Text. 3rd edn. London, Kogan Page.
Michaelis, P. R. and Wiggins, R. H. (1982) ‘A human
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1.6.5 Using speech to good effect

Speech output is a powerful way of communicating information. It has particular benefits for the visually impaired. For those whose eyesight is good, speaking lifts may seem a novelty, but they provide useful information and reassurance for the visually impaired. Some applications of the technology have less obvious benefits, such as supermarket checkouts that read out the product and prices. These were found to breach the customer's sense of privacy and to be noisy. Again, good design depend
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6.4 Using music to good effect

Music in UIs is relatively undeveloped, except in games and specialist packages designed for composers and musicians.

Some operating systems have a signature tune that is played automatically when they are loaded. This informs the user that the operating system has loaded correctly and creates a sense of identity, but can be annoying for the user if they have to listen to it repeatedly. A development on this use might be to signpost different parts of the program using musical clips.
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1.6.1 The role of sound

The use of sound is becoming increasingly common, particularly for the following types of application.

  • Applications where the eyes and attention are required away from the screen. Relevant examples include flight decks, medical applications, industrial machinery and transport. If you are a runner, you may have a heart rate monitor that allows you to monitor how fast your heart is beating. This is often indicated by an auditory beep, which spee
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1.5.2 Using animation to good effect

You can use animation for the following purposes.

  • To illustrate movement. An example of this would be an educational program that teaches about the muscles a horse uses when it runs.

  • To provide dynamic feedback. For example, in some operating systems when you are copying a number of files, an animation appears that illustrates files flying from one folder to another. This is dynamic feedback, confirming that something
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1.5.1 Different types of moving image

On paper, you can show movement by a series of diagrams each with a very small change. Figure 9 illustrates such a scenario. This has its uses, as it allows the process to be studied very carefully.

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4.2 Using images to good effect

The following are the main types of image.

  • Pictures. These include photographs, drawings and cartoons.

  • Diagrams. These include maps and other representations of relationships between objects, such as family trees and Venn diagrams. Some writers classify maps as charts. We have chosen not to do this.

  • Graphs and charts. These are visual representations of numbers. Thus, they include pie charts, h
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1.4.1 The role of images

We can use images in several ways.

  • To motivate, to attract the attention of the user, to amuse and to persuade. These uses are particularly important in advertising and marketing.

  • To communicate information. This is often exploited in computer-based learning materials.

  • To help overcome language barriers. This approach is widely used in instruction manuals for consumer items.

  • To support interaction. Fo
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1.3.5 Using colour to represent information

All UIs need to communicate information. Colour can be particularly effective for this. Table 4 summarises some of the techniques that are available.

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1.3.3 Choosing colours with the right connotations

When you use a colour, you should think about what it is likely to mean to the people who look at it, as colours can have different connotations. Colours can even make people feel different. For example, pink has been shown to have a calming effect on emotionally disturbed people.

These connotations are partly cultural, so you may find they do not ring true for you if you are a member of a non-western culture, such as Chinese or Indian. For example, in western culture, red is often used
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1.3.2 The characteristics of colour

Screens can only display a subset of the colours visible to the human eye. This limits the accuracy of colour reproduction. There is also variation between computers, so a web page on a PC may look different when viewed on a Macintosh. There are similar problems with colour printers.

These issues can cause problems for some sectors, such as the fashion industry.

There are also differences in the way we perceive colour from a screen compared to the way we perceive colour from paper
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1.3.1 The role of colour

We can use colour in the following ways.

  • To draw attention. You will often find that important buttons or areas of the screen are a different colour. For example, warning signs are often in bright colours, such as amber or red. Your eyes are drawn to these colours.

  • To show status. As the status becomes more critical, the colour might change. An example of this is traffic lights changing from amber to red.


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