In this section I've briefly considered the very contentious question of what digital representations mean, but this debate must be left to another course. I have also described some of the devices that take digital information back into the analogue world of sight and sound, presenting it in a form that is meaningful to human eyes and ears.

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Nearly all computers are supplied complete with a monitor which opens a window onto the machine's digital world. Without one we could have little idea about what the computer was doing, or even whether it was working at all.

There are two main types of monitor: the CRT (cathode ray tube) and LCD (liquid crystal display). A CRT monitor looks like a television screen, and works in a similar way to a TV or a scanner. A beam of electrons is fired from a gun at the back of the
Author(s): The Open University

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

1. Join the 200,000 students cur
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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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The number system which we all use in everyday life is called the denary representation, or sometimes the decimal representation, of numbers. In this system, the ten digits 0 to 9 are used, either singly or in ordered groups. The important point for you to grasp is that when the digits are used in ordered groups, each digit is understood to have a weighting. For example, consider the denary number 549. Here 5 has the weighting of hundreds, 4 has the weighting of tens and
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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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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

An important aspect of systems is that each component can be considered as a subsystem. In the health centre appointments system, the ‘computerised booking system’ may be a complex system in its own right involving a number of computers networked together. Figure 2 shows
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This chapter is taken from: Stone, D., Jarett, C., Woodfoffe, M. and Minocha, S. (2005) User Interface Design and Evaluation,
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For the purposes of this unit, we define a threat to an information asset as a possible way in which the asset can have its security requirements breached, and we define the outcome of a threat as the way in which the asset's security requirements would be breached if the threatened action were to occur. Recall from Section 4 that the security requirements are confidentiality, integrity and availability.

A complete picture of the relationship between an information asset,
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To preserve the value of an information asset, an organisation needs to sustain simultaneously its scarcity and its shareability within their respective regions. This is the critical high-level information security goal for any information asset; it is the entire rationale of an information security management system.

To maintain the security of an information asset, an organisation must:

• either make the information asset unavailable in i
Author(s): The Open University

## Activity 4

Read Chapter 1 of the Set Book and evaluate the case for information security made in that chapter.

### Guidance

To complete this activity, you should consider carefully the s
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Microsoft Windows is an example of an operating system (OS). These operating systems contain millions of lines of code, and inevitably there will be some errors in that code. Some malware writers set out to find these errors, or holes, in the code and exploit them to their own benefit. Whenever holes are found (by IT security people or groups, malware writers or the software developer) the operating system manufacturer will issue a fix for the particular problem. These fixes are referred to a
Author(s): The Open University

In this section we will look at two of the ways in which you can protect yourself from malware:

1. Ensure that your computer has the latest patch from Microsoft or your operating system vendor.

2. Install antivirus software that will protect you from these problems, and ensure that you keep it up to date.

(Later in this unit we will discuss firewalls, which you can also use to protect your computer.)

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The figures below show how the problem of malware has increased over the last 30 years.

1974First self-replicating code (Xerox)
1982First virus on the Apple platform
1984First conference papers on viruses presented
1986First recorded virus infection on the PC
19
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All materials included in this unit are derived from content originated at the Open University.

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Let's start by brainstorming the impact that access to information on the Web has had on you and on the people with whom you are in contact.

### Activity 34

Make a list of the advantages and disadvantages of getting information from
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An immediate temptation is to head straight for a search engine such as Google and enter your family name, but a moment's thought should warn you that the results will be disappointing. This is particularly so if your name is common or, like White or Snow, is also an English word. Even a relatively uncommon family name such as Rosewell turns out to be a place name in both Scotland and the USA and a misspelling of a UFO.

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Most browsers allow you to keep a record of links to websites that you have found useful. These are called ‘Bookmarks’ in Firefox and ‘Favorites’ in Internet Explorer, and may have other names, such as a ‘Hot List’, in other browsers. For convenience I've chosen to call them bookmarks. Browsers usually offer the facility for organising the bookmarks into folders and sub-folders so that you can keep track of them as your collection grows.

You may well have a collection of boo
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## Activity 32: exploratory

What is the smallest RFID tag currently available? Use the Web to see what you can come up with but don't spend longer than 10 minutes on this activity. (Hint: using ‘smallest RFID tag’ as the search term w
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