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14.1 Introduction

Now that I have introduced you to the processes carried out by a stand-alone computer, I will move on to discuss what happens when computers are linked.


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13.2 Magnetic storage

As I mentioned earlier, your computer has a hard disk which provides a permanent storage area for your computer's programs and the files you create. When you save files to your computer's hard disk, you are using a magnetic storage medium. Data stored in magnetic form can be changed once it has been stored, so if you run out of space you can delete some files to make room or, if you want to edit a file, you can make the necessary changes and then save it again. At the time of writing, a mediu
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12.1 Introduction

Data must be stored somewhere when it is not being manipulated. Modern ICT systems require increasingly large amounts of data to be stored for later use, and it is important that the data can be accessed quickly. Data may be stored on the stand-alone computer's hard disk in the form of files.

You may want to move files from one stand-alone computer to another. In addition, you may want to move files from a device, such as a digital camera, to a computer. These activities require some fo
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11.4 Computer software

The electronic components and other equipment that make up your computer system are known as hardware. In order to make the computer do things, such as help you to produce your TMAs, edit photographs or draw diagrams, you also need computer programs, which are called software.


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11.2 The processor

The processor can be thought of as the ‘brain’ of the computer in that it manages everything the computer does. A processor is contained on a single microchip or ‘chip’. A chip is a small, thin slice of silicon, which might measure only a centimetre across but can contain hundreds of millions of transistors. The transistors are joined together into circuits by tiny wires which can be more than a hundred times thinner than a human hair. These tiny circuits enable t
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11.1 Introduction

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


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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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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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4.1.1 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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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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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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4.6 False identification

If you think back to the Heathrow experimental system and the United Arab Emirates system described earlier, you can see that the false matches and false non-matches open up possibilities for these systems to malfunction. In the Heathrow scheme, a false match could mean that a person who was not enrolled might be allowed through. In the United Arab Emirates scheme, a false non-match might mean that a person who should be stopped is allowed through. These are examples of identification error.<
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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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3.4 Using a query language

When you search a large website for information, for instance when you search a large e-government site, very often, behind the scenes, a large relational database is being searched. I mentioned earlier the use of SQL as a way of extracting information from a database. Depending on the system being used, your enquiry may be converted into an SQL query, and this finds the information you need. For example, suppose we wanted to find the family names of all people enrolled on the digital photogr
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3.3 Entities and attributes

A well-designed relational database overcomes the problems outlined in Section 3.2 by using two or more tables, rather than a single table, such as Table 1. This means that the data has to be divided in some way between the tables. The construction of tables is done according to several rules.
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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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2.1 The role of text

Text is the dominant component in most education and training software, and on many websites. It also plays a central role in standard software applications such as word processors and spreadsheets. It is a flexible and powerful means of communication.

Activity 1


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Other approaches to information security management

Many of the approaches to planning an ISMS to be found in the literature follow a three-phase, rather than a four-task, approach. For instance, Moses (1994) stipulates seven steps in three phases:

  • initiation: the identification of information assets and their security requirements;

  • analysis: the identification of possible risks to the security requirements of information assets, of the vulnerabilities to those risks, and
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5.2.3 Risk assessment

The risk assessment task is also carried out at unit level, in light of policies set out in Stages 1 to 3 and for the assets identified in Stage 4.1.

  • Stages 4.2, 4.3 and 4.4: identify the risks

  • Stage 4.2 determines systematically the possible threats to the assets identified in the asset identification part of the process. (Clause 4.2.1(d)(2))

  • Stage 4.3 identifies vulnerabilities that might allo
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