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Learning outcomes

Having studied this unit, you should be able to:

  • give examples of quantities that are intrinsically analogue, and quantities that are intrinsically discrete/digital;

  • define the terms ‘bit’, ‘byte’ and ‘word’;

  • outline how visual information, such as pictures, diagrams and moving images can be expressed numerically inside a computer;

  • describe how sounds such as speech and music can be represented inside a computer in terms
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Acknowledgements

All materials included in this unit are derived from content originated at the Open University.

Except for third party materials and otherwise stated (see terms and conditions), this content is made available under a Creative Commons Attribution-NonCommercial-ShareAlike 2.0 Licence
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8.3 The AND operation

The AND operation combines two binary words bit by bit according to the rules

  • 0 AND 0 = 0

  • 0 AND 1 = 0

  • 1 AND 0 = 0

  • 1 AND 1 = 1

In other words, only when both bits are 1 is the result 1. You may find it helpful to think of it this way: when one bit is one and the other bit is 1 the result is 1.

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7.6 Arithmetic with binary fractions

My final point in the preceding section brings home the fact that integer arithmetic is not really suitable when divisions are to be performed. It is also not suitable where some or all of the values involved in the arithmetic are not – or are not necessarily – integers, and this is often the case. In such cases, arithmetic has to be performed on non-integers.

The most common representation for non-integers is the floating-point representation that I mentioned briefly in Box 3. You
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7.1 Adding unsigned integers

Study note: You may like to have the Numeracy Resource (attached below) to hand as you study Section 7. It offers extra practice with the manipulations, and you may find this useful.

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

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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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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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16.2 Processes at the checkout

From the point of view of the customer and the checkout operator, a supermarket's ICT system is like the stand-alone computer you saw in Figure 10 in Section 9. The system map in Author(s): The Open University

13.3 Optical storage

A CD-ROM (Compact Disk Read Only Memory) uses a laser-based optical form of storage. This type of disk has been used for many years to distribute music and computer software. A CD-ROM drive is needed to read the disks. Data is locked into the disk during manufacture, and cannot afterwards be changed.

There are two other types of CD device for computers: CD-R (CD-recordable) and CD-RW (CD-rewritable). With the right sort of CD drive in your computer, you can ‘burn’ data (that
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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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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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Learning outcomes

This is what you should have achieved when you have completed your study of this unit:

  • Understand the concept of e-government, and the associated benefits and drawbacks.

  • Understand how a relational database differs from a flat database, including the function and construction of a joining table.

  • Understand some of the basic principles of XML.

  • Understand the basic principles of biometric identification and verification systems


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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 analy
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6.2.3 Likelihood, impact and risk

Having looked at threats, vulnerabilities, outcomes and impacts, we are now in a position to offer a definition of risk with regard to threats to the information assets of an organisation. This definition will lead to an approach to measuring and assessing risk that is consistent with the Standard and with IT Governance: A Manager's Guide to Data Security & BS 7799/ISO 177799 (the Set Book). This systematic approach to risk assessment corresponds to Stage 3 of the ISMS documentation ta
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5.4 ISMS documentation

In this subsection we shall consider Stages 1, 2 and 8 of the ISMS documentation task. Stage 3 is considered in Section 6. We shall not discuss Stage 9 in this course.


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5.2.1 ISMS documentation

ISMS documentation is carried out at organisation level. Its purpose is to define the scope and context of the proposed system, and the approach to information security management that it will embody. It has five stages: three that initiate the planning process (Stages 1 to 3) and two that complete it (Stages 8 and 9).

  • Stage 1: define the scope of the ISMS The context and scope of the ISMS are defined by considering the nature of the organisat
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3.2.3. Regulation and codes of conduct

Chapter 1 of the Set Book presents a case for effective information security based largely upon perceived threats and legal obligations. Chapter 2 introduces further imperatives, which govern specific types of organisation in the UK.

Activity 6


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2.3 What is information security management?

Information security management is the process by which the value of each of an organisation's information assets is assessed and, if appropriate, protected on an ongoing basis. The information an organisation holds will be stored, used and transmitted using various media, some of which will be tangible – paper, for example – and some intangible – such as the ideas in employees' minds. Preserving the value of information is mainly a question of protecting the media in which it is
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2.1 What is information?

Information comprises the meanings and interpretations that people place upon facts, or data. The value of information springs from the ways it is interpreted and applied to make products, to provide services, and so on.

Many modern writers look at organisations in terms of the use they make of information. For instance, one particularly successful model of business is based on the assets that a firm owns. Assets have traditionally meant tangible things like money, property, plan
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