Capturing bits of reality and transferring them to a computer would be a pointless exercise if they stayed locked in the digital world. We want access to what we've captured. We want to see the results. In particular, we may want to look at our captive in a different form. For instance, suppose we input the series of temperature readings shown in Author(s): The Open University

In this unit, I want to be more specific and look at the way computers represent and handle data. The unit aims to:

• broaden the definition of a computer and explain the concept of crossing the boundary between the computer's world and our own

• explain the digital nature of the computer's world and contrast it with our analogue world of sense and motion

• describe in detail how to transform features of our world i
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This unit introduces the important distinction between our analogue world of colour, sound, taste and touch and the computer's peculiar binary world of digital entities. Concepts of the analogue universe in which we live and the digital world we create are explained. The way in which information, in the form of text, still and moving images, and sound can cross the boundary from the analogue universe into a digital world is explored.

This unit is from our archive and is an adapted extr
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The OR operation (occasionally called the inclusive-OR operation to distinguish it more clearly from the exclusive-OR operation which I shall be introducing shortly) combines binary words bit by bit according to the rules:

• 0 OR 0 = 0

• 0 OR 1 = 1

• 1 OR 0 = 1

• 1 OR 1 = 1

In other words, the result is 1 when either bit is 1 or when both bits are 1; alternativel
Author(s): The Open University

Study note: You may like to have the Numeracy Resource to hand as you study Section 15. It offers extra practice with the logic operations, and you may find this useful.

Author(s): The Open University

You will probably have carried out subtraction of denary numbers using rules for subtraction that include the process of â€˜borrowingâ€™ whenever you need to subtract a larger digit from a smaller one. It is possible to perform binary subtraction in a very similar way, but that is not what happens in computers. The processor contains the circuits needed to perform addition, and it is much more efficient to use these circuits also to perform subtraction than it is to build in extra circuits to
Author(s): The Open University

A very straightforward way of finding binary codes to represent positive integers is simply to use the binary number that corresponds to each integer. This is because every positive integer in the everyday number system (known as the decimal or denary system because it uses 10 different digits) has a corresponding number in the binary number system.

As you will see later, in Section 7 of this unit, just as arithmetic (addition, subtraction, etc.) can be performed on everyday denary numb
Author(s): The Open University

In a supermarket ICT system, there needs to be some way for the computer to receive information about the items a customer is buying.

## Activity 13 (exploratory)

Think back to a recent visit to your local supermarket and how you ma
Author(s): The Open University

Flash memory is an electronic form of memory which can be used, erased and reused. A flash memory card is a small storage device used to store data such as text, pictures, sound and video. These cards are used in portable devices such as digital cameras and in small portable computers, such as Personal Digital Assistants (PDAs).

A USB flash memory, sometimes called a â€˜memory stickâ€™, is a small storage device which is completely external and connects to the computer via a USB
Author(s): The Open University

The processor can be thought of as the â€˜brainâ€™ of the computer in that it manages everything the computer does. A processor is contained on a single microchip or â€˜chipâ€™. 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
Author(s): The Open University

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
Author(s): The Open University

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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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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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
Author(s): The Open University

This unit has discussed the importance of information assets to any modern organisation and has made the case for information security management. It has introduced you to extracts from the British Standard on Information Security Management and to the approach advocated in the Standard for establishing and managing an information security management system (ISMS). It has also introduced the PDCA cycle. A particular focus in this unit has been on the planning of an ISMS, and on the four tasks
Author(s): The Open University

A hacker who threatens your organisation's information assets is taking advantage of vulnerabilities in the media and systems which handle them. Vulnerabilities and threats clearly go hand-in-hand: each threat is directed at a vulnerability.

The relationship between information assets, threats, vulnerabilities and existing defences is illustrated in Author(s): The Open University

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 unit.

Author(s): The Open University

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 organisa
Author(s): The Open University

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

Author(s): The Open University

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 â€“ paper, for example â€“ and some intangible â€“ such as the ideas in employees' minds. Preserving the value of information is mainly a question of protecting the media in which it is
Author(s): The Open University