11.1 Introduction

A stand-alone computer needs two main components to manipulate data: a processor and a working memory.


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10.2 Ports

On the outside of a computer you will see a number of connection points that look like sockets. These sockets are known as ports and they provide connections between the computer and external devices such as a digital camera or printer. Ports control the flow of data between the computer and these devices, ensuring that data is sent and received quickly and reliably.

Modern ICT devices require increasingly large amounts of data to be sent between the computer and the devices. The
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10.1 Introduction

A stand-alone computer receives data from a user by means of input devices. The two most commonly used input devices are the keyboard and the mouse. A computer sends data to a user by means of output devices. Data may be output via devices such as a screen or a printer.

There are many different ways of getting data into a computer. For example, a scanner converts images and texts into a format that can be processed by the computer and displayed on screen. Devices such as t
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9 A stand-alone computer

The computer you are using for your studies is called a personal computer or PC. Although you have an internet connection for use in this course, your computer can probably also be used as a stand-alone computer. Your PC may be a desktop computer or a notebook computer (sometimes known as a laptop computer). Usually a desktop computer comes with separate devices such as a monitor, a keyboard, a mouse and speakers and it runs on mains electricity. Notebook computers
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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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6.2 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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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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5 The processes

My description of the three subsystems of ‘means of conveying a message’ has indicated some important processes that each carries out. These are shown in Figure 8. The key processes are those that will always be carried out and they are shown in bold; the other processes may or may
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4.1.2 The network

The network is a communication channel in that it conveys data from the transmitter to the receiver. The network may also manipulate data in some way, and it may also store or retrieve data.

In a mobile phone system, the network conveys the message from User l's handset to User 2's. It will also store the identity of User 1 and the duration of the call. This data is used to work out the amount to charge User 1, which is a form of manipulation of data. A network can be very comple
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4.1.1 The transmitter

The transmitter receives a message from User 1 and manipulates it into data which can be sent into the network. The transmitter may also store or retrieve data relating to the message.

In the mobile phone system, the transmitter, which is User l's mobile phone, receives a message from User 1 in the form of sound. It manipulates the incoming sound into a data format suitable for sending into the mobile phone network. Even basic models of mobile phone handsets can store names and telephon
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4.1 Introduction

I'll now look at what these components do in the communication system, using the mobile phone system as an example.


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3.2 Looking into the 'means of conveying a message'

The diagram in Figure 6 shows that, for communication to take place, there needs to be some means of conveying the message between the sender and the recipient. I am now going to look at the essential components of ‘means of conveying a message’. In other words, I shall treat ‘m
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2.3 Models of an ICT system

To help me to introduce you to important ideas about ICT systems, I'm going to take a three-stage approach. ICTs involve conveying, manipulating and storing data. This is going to be the basis of my approach.

Firstly, in the next few sections, we'll look at ICT systems where the primary function is to convey data. We can think of these systems as communication systems and I'll use a mobile phone system as an example.

In sections 8–14, I'll focus on ICT systems wher
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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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4.5 Typical false match rates

A false match rate is expressed as a statistic such as ‘1 in 1000’. A rate of 1 in 1000 means that if a sample of biometric data is compared with random selections of other data, a false match occurs, on average, once every 1000 comparisons. False match rates vary widely between different biometric systems. The following figures are taken from Mansfield and Rejman-Greene (2003).

Using good-quality fingerprints, a false match rate for single prints can be around 1 in 100,000. This ra
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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

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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7.2 Difficulties in navigating e-commerce sites

People who are new to computing sometimes find the process of online ordering baffling and frustrating. They get ‘lost’ in the process – for example, by putting something into a virtual shopping cart and then remembering that there's something else they need to look for. So they return to the search engine or the catalogue and then can't find the cart. These kinds of commonly experienced difficulties can be addressed by good and adaptive site design, but still a disturbing proportion of
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6.2 Authority and the variety of information sources

Technology has massively increased the number and variety of news sources that we have access to. We still have printed books, magazines and newspapers, while digital techniques have increased the number of broadcast radio and TV channels that we can get. On the Web we have access to online versions of many of these. This allows us access to media that previously would have been inaccessible.

With traditional news sources such as these, we have some understanding of the authority that t
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