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2.2.2 Positive integers: binary numbers

Just as a denary number system uses ten different digits (0, 1, 2, 3, … 9), a binary number system uses two (0, 1).

Once again the idea of positional notation is important. You have just seen that the weightings which apply to the digits in a denary number are the exponents of ten. With binary numbers, where only two digits are used, the weightings applied to the digits are exponents of two.

The rightmost bit is given the weighting of 2°, which is 1. The ne
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3.1 Introduction

Generally, when we talk about communication between humans, we mean one person conveying information to another person. Figure 6 shows a basic model, or representation, of a communication system for getting a message from the sender to the recipient. The diagram shows the sender (User
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Introduction

This unit is from our archive and it is an adapted extract from Networked living: exploring information and communication technologies (T175) which is no longer in presentation. If you wish to study formally at The Open University, you may wish to explore the courses we offer in this curriculum area.

This unit will introduce you to some ideas about how information and
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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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3.5 Other kinds of data

All the data we have had so far in the database has been text or numbers. I have mentioned that another type of data might be dates. Modern databases, however, can store other kinds of data than text, numbers and dates. They can also store graphics, moving pictures and sounds.

Activity 12 (exploratory)
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1 E-government

In many countries, e-government has become part of government policy. The UK government has a large e-government project under way, as do the governments of the USA, Australia and Japan, to name just a few. The ‘e’ at the start of ‘e-government’ stands for ‘electronic’, and e-government usually refers to the use by governments of ICTs. In many ways e-government is not a single activity but many activities. However, in the UK and many other countries, there is a degree of central c
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1.6.2 Different types of sound

Sounds come in four categories.

  • Sound effects. Many UIs contain a range of warning beeps and reassuring sounds confirming that operations have been completed. These can include naturalistic sounds, such as the sound of a piece of screwed-up paper dropping into a waste paper basket.

  • Music. Many composers use computer systems to compose music, and programs such as games make extensive use of music. Short sequences of mus
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1.3.4 How to use colour to good effect

The effective use of colour is a complex and technical area. In Table 2 we have listed some general guidelines.

Table 2: Making e
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References

Alberts, Christopher and Dorofee, Audrey (2003) Managing Information Security Risks: The OCTAVE Approach, Addision-Wesley.
Grant, Robert M (1998) Contemporary Strategy Analysis (3rd edn), Blackwell.
Itami, H and Roehl, T (1987) Mobilizing Invisible Assets, Harvard University Press.
Moses, Robin (1992) ‘Risk an
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7.3 ADV:

Some spam mail includes ‘ADV:’ in the title. This indicates that it is part of the system used in the US to allow spam mail but to highlight that it is an advertisement. You can then make an informed choice as to whether to read or delete the message.

ADV: also allows users of email systems that have filtering facilities, such as Outlook, Eudora or Pegasus, to set a rule that will automatically remove the message. The way this works is that some email systems allow you to define a s
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1 What this unit is about

The recent huge increases in ownership of home computers and ever-widening access have been obvious boons to many peoples' lives but, as with many things that improve life, there is a downside. The downside with computers is that software crashes, hardware fails and some Internet users want to cause havoc or vandalise your computer. In this unit we will look at a few of the problems that other people may cause you.

Normally when we talk about malicious software we are referring to virus
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3.1 Searching for your ancestors

In this section we consider searching for information about your ancestors. We cannot hope to cover all the techniques and information required to research genealogy, family history and local history; there is only time in this unit to scratch the surface. Some of the activities here are open-ended; please do not spend too long on them. If the subject interests you, you can revisit it after the course finishes, making use of the genealogical resources in the Appendix.


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4.4 An introduction to WiFi

WiFi (from ‘Wireless Fidelity’) is used to connect devices together in one of two network configurations known as ‘ad hoc’ and ‘infrastructure’. We shall explain these terms shortly. (As a starting point, though, you could look up the terms ‘ad hoc’ and ‘infrastructure’ in your dictionary.)

In wireless LANs, nodes are usually referred to as stations – probably because each communicating device acts as a radio station with transmitter and receiver. These func
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4.2 Basic principles of wireless transmission

I've never quite lost the sense of wonder at the way information can be transmitted with no visible link between the sender and recipient. When I was a child I used to think that sound came through the wire linking my family's radio to the mains electricity supply (I was born before the days of battery-powered transistor radios) and I couldn't understand why my parents referred to it as ‘the wireless’ – since clearly it wasn't. I now know that the wire simply fed the radio with the elec
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4.1 Introduction

The focus of Section 3 was on LANs that use some kind of physical medium (for example, copper wires or fibre-optic cables) to connect together network nodes. In this section we'll be examining wireless networks – that is, networks that transmit data through the air (or space) using radio waves.

There's nothing new about wireless: the principles of transmitting information using radio waves were discovered over a century ago. However, using radio waves to provide the transmission links
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2.2 What are signals?

To convey data from one point to another we need to represent the data by means of a signal. We can think of a signal as a deliberate variation in some property of the medium used to convey the data. Some examples are:

  • an electrical voltage travelling along copper wires between your telephone and the local exchange;

  • pulses of light (though we might not be able to see them) in a fibre-optic cable;

  • the radio emissions t
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1.1 Getting an overview

This section starts with an article from a technical journal – the sort that is read by academics and professionals working in a related technical field. It sets the scene for some of the technologies and issues that you will be encountering later in this unit.

We're not going to ask you to read the entire article, but we would like you to get an idea of the article's contents, the kind of points the author is making, and the range of issues that it throws up. With this aim in mind, w
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Learning outcomes

When you have completed your study of this unit, you should be able to:

  • understand and use correctly terms introduced in this unit in relation to communication networks;

  • understand general principles involved in data exchange between ICT devices;

  • work with numbers expressed in scientific notation, and use the Windows calculator to perform calculations on these numbers.


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Acknowledgements

The content acknowledged below is Proprietary (see terms and conditions). This content is made available under a Creative Commons Attribution-NonCommercial-ShareAlike 2.0 Licence

Grateful acknowledgement is made to the following sources for permission to reproduce material in this unit:

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2 2 Conclusion

The versatile tiny transistor is now at the heart of the electronics industry. In the video clips you have seen the history of the incredible shrinking chip, its Scottish connections, and an explanation of the physics that make chips work as well as a reconstruction of making a transistor using the crude techniques of yesteryear.


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