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Headache

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2.1 Introduction

Study note: You may like to click on the link below to the Numeracy Resource as you study Section 2. It offers additional explanations and extra practice on some of the topics, and you may find this useful.

Click on the 'View document' link below to open the Numeracy Resource.
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1 Representing data in computers: introduction

A computer is designed to do the following things:

  • receive data from the outside world;

  • store that data;

  • manipulate that data, probably creating and storing more data while doing so;

  • present data back to the outside world.

In the next few sections I am going to examine in more detail the data that a computer receives, stores, manipulates and presents. I
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16.1 Introduction

Supermarkets make use of ICT systems for a range of purposes. In the following sections, we'll look at the processes of receiving, storing, retrieving, manipulating and sending data at the checkout, and then we'll move on to the larger context of the supermarket.


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4.2.3 Second computer (the FirstClass server)

The computer on the right of Figure 11 receives the data, manipulates it and then stores it. The computer then typically sends some kind of response back via the network, which may require the computer to retrieve some stored data.

The computer in this example is one of the Ope
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4.2.2 Network

In the same way as in the network shown in Figure 8, this network conveys the data to the receiver, selecting the most appropriate route for it to travel. In order to do this, the network may need to manipulate and store or retrieve data.

Your computer sends the FirstClass message
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12.2 Bytes of data

You will recall from Section 6.2 that a binary digit, or bit, can have one of two values: either a 0 or a 1. In a computer, bits are assembled into groups of eight, and a group of eight bits is known as a byte. The abbreviation used for a byte is B, so 512 bytes would be written as 512 B. Although this course will use ‘b’ for bit and ‘B’ for byte, you should be aware that not everyone makes this clear distinction.

A byte of data can represent many different things in a co
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8 Computers

In sections 8–14, I am going to start by considering a stand-alone computer, which is a computer that is not connected to a network. In this type of ICT system, the key processes are the manipulation and storage of data. I'll be introducing some details about the way that a computer manipulates and stores data. Then I'll be discussing the processes that are carried out by computers when they are linked.


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7 Describing an ICT system: conclusion

We have arrived at a model of a communication system that illustrates the processes needed for communication. We have also looked at the different kinds of communication link that can be used to convey data, and how to express the rates at which they can convey data. In sections 8–14, we shall be looking at a computer system as an example of an ICT system where data manipulation and storage are the most important features.


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6.1 Networks

Next I'll be looking more closely at the ‘network’ block in Figure 8, and in particular at the links that must be present before communication can take place. I'll introduce you to just a few of the forms that these links can take; links may be physical ones, such as cables, or they
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4.1.3 The receiver

The receiver receives data from the network and manipulates it into a message to send to User 2. Sometimes the receiver may also store or retrieve data.

In the mobile phone communication system, the data received from the network must be manipulated back into sound before being sent to the user. In addition, some mobile phones can store and retrieve data about the user's contacts, so that when a call is received they can translate the phone number of the caller into a name which is then
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2.2.2 Drawing the boundary

Deciding where to place the system boundary is an important consideration in that we have to think about what to include and exclude. This isn't always an easy decision to make and it often depends on the perspective of the person viewing the system.

The system maps in Figures 1
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2.2 A system map

One way of explaining and analysing a system is to represent it in a graphical form, known as a system map. I'll use the example of a system for making an appointment with a doctor in a health centre to illustrate this point. In this example, the health centre uses a computerised booking system and the patient may phone or visit the health centre to make an appointment. Therefore, the system includes a patient, a receptionist, a doctor, and a computerised booking system. The example sh
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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.

Many governments across the world are moving towards the use of infor
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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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7.5 Active and passive tags

Activity 30: exploratory

Read the extracts below. Using the information they contain, make notes about the main differences between active and passive RFID tags. You will get more out of this exercise if you make a serious attempt to d
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3.1 Introduction

This section starts by broadly classifying different types of network, first by the nature of the communication links used to connect devices and then by a network's geographical spread. It then examines in more detail a network which uses a cabled communication link.

A networked device is often referred to as a node so we shall use this term in the sections that follow. A node is any device (for example, computer, printer, server) connected to a network, either as an end point (
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2.8 Attenuation and distortion

As a signal travels from one device to another it has two problems to overcome. The first is that it gets weaker the further it travels, because some of its energy is absorbed by the transmission medium. This effect is known as attenuation. The extent of attenuation depends on the distance it has to travel and on the type of medium it is travelling through. An amplifier can be used to boost the signal power at the transmitter and receiver, and if necessary at various points in the tran
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4 The eBay phenomenon – what it means

Writers on e-business group Internet processes into four categories, using this grid:

Figure 13
Figure
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