3.9 A few more terms

Just to round off this description of the interior of the digital world, let me introduce and define a few more terms that you will come across again in this course and in any future studies of computers. Specifically, you may have heard the terms bits, bytes and words used in connection with computers. Now that we have taken a look at the binary system that underlies computer arithmetic, you will find there is no mystery in any of these three terms.

The word Bit is
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3.3.1 The human perceptual system

In order to survive, all living things have evolved some sort of ability to sense or perceive the world around them. Even the humble amoeba is sensitive to light. Complex animals have intricate perceptual systems that respond to many different features of their environment – insects, despite their impressive eyes, are most sensitive to trails of chemicals; bats are blind to light but responsive to sonar pulses; dogs and pigs depend more on smell than vision for sensing the world.

We w
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2.9 Summary

In this section, I started by emphasising the fact that the computer, which has become more or less omnipresent in modern society, is a tool like any other.

I went on to look at the special nature of that tool, establishing that its function is to capture, store, present, exchange and manipulate interesting aspects of the world.

I then introduced the idea of two contrasting realms: the analogue world we inhabit and the digital interior world of the computer. When we capture featur
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2.7 Manipulation

As I suggested above, we can change a digital version of some aspect of reality in any way we want. I've used the simple example of tinkering with a digital photograph, but the possibilities for transformation go far beyond this. We can set up elaborate replicas of real-world systems and inspect them in detail. We can establish digital models and run them forward in time to see what might happen in the future. We can even create completely imaginary digital worlds and then explore them as if
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2.5: Crossing the boundary

So computers are used to acquire, store and present, exchange, and manipulate interesting characteristics of the world. But this raises a serious problem: the world we inhabit and know so well and the world inside the computer are very different in kind. We live in an analogue world. The world of the computer is digital. The exact meaning of these terms may not be very clear to you at the moment. I will define them both in the next section. For the moment, the only point
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8.4 The OR operation

The OR operation (occasionally called the inclusive-OR operation to distinguish it more clearly from the exclusive-OR operation which I shall be introducing shortly) combines binary words bit by bit according to the rules:

  • 0 OR 0 = 0

  • 0 OR 1 = 1

  • 1 OR 0 = 1

  • 1 OR 1 = 1

In other words, the result is 1 when either bit is 1 or when both bits are 1; alternativel
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4.2 Representing text

Study note: You will need to refer to the Reference Manual while you are working through this section.

Please click on the 'View document' link below to read the Reference Manual.

References

Revell, P. (September, 2004) Miniature computers are adding up to fun [online] http://education.guardian.co.uk/elearning [story[0,10577,1314016,00.html Accessed 16 October 2006] Guardian Newspapers Ltd.

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18.2 Using e-commerce

Many people now have internet connections and this offers many benefits to both businesses and their customers.

From a customer's point of view, e-commerce has a number of advantages. Shopping can be done from home; you can probably find what you need without trudging from one shop to another and waiting in queues. You can also purchase goods 24 hours a day, every day.

From the point of view of a business, e-commerce also offers a number of advantages. There is a potentially wide
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17.2 The checkout terminal

The first computer block represents the checkout terminal. The processes at the checkout (receiving, storing, retrieving, manipulating and sending data to the user), are the same as I described earlier. However, the checkout terminal also sends data via the supermarket's network.


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16.9 Identity in an ICT system

In a supermarket we might see the following data on an item: 5018190009067. On their own, the digits do not mean very much, but these numbers are typical of the type of data input to a computer system. In this instance, they are numbers from a bar code on a jar of coffee. I have described the numbers here as ‘data’ because in themselves they do not really tell us anything.

When the bar code is moved past a bar code reader at a checkout counter, the checkout terminal will display det
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16.2.3 Manipulating data

Once all items have been scanned, the checkout computer manipulates the data to produce the total cost. If you are paying with cash and require change, the checkout operator will enter the amount you have tendered (an example of the computer receiving data from the user) and the computer will calculate any change required.


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6.2 Working with bits

You may have met the term bit, perhaps in connection with computers. The term ‘bit’ is also important in communication systems. It is an abbreviation for ‘binary digit’. A binary digit can have just one of two values: it can be either 1 or 0. Pulses can be represented by 1s and 0s, that is, as bits, and so it is convenient to think of streams of 1s and 0s being conveyed along the communications link.

The rate at which the 1s and 0s are conveyed is known as the data rat
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1 Describing an ICT system

In this unit I shall be introducing you to some ideas about how ICT systems work. Because this unit is about ICT systems, I'll be starting with a discussion about what constitutes a system. I'll go on to introduce some diagrammatic ways of representing ICT systems. Then I'll look at some examples to illustrate how they carry out certain processes, namely conveying, storing and manipulating data. You will also find out about other processes performed by ICT systems.

In this sectio
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3.6 Viewing the data

Reverting to the relational database we constructed in Section 3.3, you might wonder what, from the user's point of view, has been gained by creating separate tables for the students and courses. With Table 1 you could see at a glance who was studying what. In the relational database it was har
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2.1 Modernising government

Before we start to look at e-government itself, I would like you to read some quotations. During the 1980s and 1990s, the potential of ICT systems for government was discussed by many commentators, but in the UK the official argument for e-government was set out in 1999 in the document Modernising Government. This document, however, is not specifically about e-government. Rather, it is about the much broader issue of how government should be modernised. Here is an extract:


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1 1 Getting the best from interaction devices

Once we have chosen an interaction device for a user interface, we need to consider how to use it effectively. We have relatively little control over the appearance or use of input devices, so we concentrate on the design of the feedback provided by output devices. In particular, we concentrate on the following software components that form this feedback.

  • Text. How can we ensure that the text is legible? Which font should we use? How long shou
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5.2.4 Risk treatment

The risk treatment task is again carried out at unit level, in light of polices set out in Stages 1 to 3. The risks treated are those chosen for control at Stage 6.

  • Stage 7: select control objectives and controls For each risk chosen for control at Stage 6, a suitable control (countermeasure) must be selected from those suggested in the Standard or from elsewhere. The risks are treated in order of priority, according to the priority levels as
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11.4 Controlling cookies in Firefox

  • Open your browser.

  • On the top menu bar of the browser choose Tools > Options.

  • Then choose Privacy in the left panel and expand the Cookies heading.

9 Adware and spyware

The previous sections of this topic have been concerned with email, but the Internet provides yet more problems, in the form of adware and spyware on the Web. You may have seen pop-up messages on your browser screen offering services or products. What you may not realise is that if you respond to these messages, extra software may be installed alongside other programs without your knowledge.

Adware

Adware is ‘free’ software that is subsidised by displaying adverts


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