They are neither finite quantities, or quantities infinitely small, nor yet nothing. May we not call them the ghosts of departed quantities?

(Bishop G. Berkeley, The Analyst)

This section follows up the ideas presented in and aims to:

• define the terms analogue, discrete and digital;

• look briefly at the human perceptual system, whic
Author(s): The Open University

Suppose I take a digital photograph of myself for my website. Horrified by my wrinkled, baggy appearance, what can I do? Actually, with the right software I can do more or less anything I like: I can smooth out the wrinkles; I can restore the grey hair to its former splendour; I can even put in a background of books to give me a scholarly appearance. In fact, I can so improve the picture that if you met the real me you probably wouldn't recognise me.

â€˜Massagingâ€™ my photographic imag
Author(s): The Open University

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.

Author(s): The Open University

Multiplication can be thought of as repeated addition. For instance, in denary arithmetic

7 Ã— 5

can be thought of as

7 + 7 + 7 + 7 + 7

There is therefore no need for a new process for the multiplication of binary integers; multiplication can be transformed into repeated addition.

In multiplication the result is very often much larger than either of the two integers being multiplied, and so a multiple-length representation may be needed to hold the result of a mu
Author(s): The Open University

If computers encode the denary numbers of the everyday world as binary numbers, then clearly there needs to be conversion from denary to binary and vice versa. You have just seen how to convert binary numbers to denary, because I did a couple of examples to show you how binary numbers â€˜workâ€™. But how can denary numbers be converted to binary? I'll show you by means of an example.

Author(s): The Open University

Just as a denary number system uses ten different digits (0, 1, 2, 3, â€¦ 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 2Â°, which is 1. The ne
Author(s): The Open University

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
Author(s): The Open University

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.

This unit will introduce you to some ideas about how information and
Author(s): The Open University

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
Author(s): The Open University

All the data we have had so far in the database has been text or numbers. I have mentioned that another type of data might be dates. Modern databases, however, can store other kinds of data than text, numbers and dates. They can also store graphics, moving pictures and sounds.

## Activity 12 (exploratory)Author(s): The Open UniversityLicense informationRelated contentExcept for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

In many countries, e-government has become part of government policy. The UK government has a large e-government project under way, as do the governments of the USA, Australia and Japan, to name just a few. The â€˜eâ€™ at the start of â€˜e-governmentâ€™ stands for â€˜electronicâ€™, and e-government usually refers to the use by governments of ICTs. In many ways e-government is not a single activity but many activities. However, in the UK and many other countries, there is a degree of central c
Author(s): The Open University

Sounds come in four categories.

• Sound effects. Many UIs contain a range of warning beeps and reassuring sounds confirming that operations have been completed. These can include naturalistic sounds, such as the sound of a piece of screwed-up paper dropping into a waste paper basket.

• Music. Many composers use computer systems to compose music, and programs such as games make extensive use of music. Short sequences of mus
Author(s): The Open University

The effective use of colour is a complex and technical area. In Table 2 we have listed some general guidelines.

## Table 2: Making eAuthor(s): The Open UniversityLicense informationRelated contentExcept for third party materials and/or otherwise stated (see terms and conditions) the content in OpenLearn is released for use under the terms of the Creative Commons Attribution-NonCommercial-Share

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) â€˜Risk an
Author(s): The Open University

Some spam mail includes â€˜ADV:â€™ in the title. This indicates that it is part of the system used in the US to allow spam mail but to highlight that it is an advertisement. You can then make an informed choice as to whether to read or delete the message.

ADV: also allows users of email systems that have filtering facilities, such as Outlook, Eudora or Pegasus, to set a rule that will automatically remove the message. The way this works is that some email systems allow you to define a s
Author(s): The Open University

The recent huge increases in ownership of home computers and ever-widening access have been obvious boons to many peoples' lives but, as with many things that improve life, there is a downside. The downside with computers is that software crashes, hardware fails and some Internet users want to cause havoc or vandalise your computer. In this unit we will look at a few of the problems that other people may cause you.

Normally when we talk about malicious software we are referring to virus
Author(s): The Open University

In this section we consider searching for information about your ancestors. We cannot hope to cover all the techniques and information required to research genealogy, family history and local history; there is only time in this unit to scratch the surface. Some of the activities here are open-ended; please do not spend too long on them. If the subject interests you, you can revisit it after the course finishes, making use of the genealogical resources in the Appendix.

Author(s): The Open University

WiFi (from â€˜Wireless Fidelityâ€™) is used to connect devices together in one of two network configurations known as â€˜ad hocâ€™ and â€˜infrastructureâ€™. We shall explain these terms shortly. (As a starting point, though, you could look up the terms â€˜ad hocâ€™ and â€˜infrastructureâ€™ in your dictionary.)

In wireless LANs, nodes are usually referred to as stations â€“ probably because each communicating device acts as a radio station with transmitter and receiver. These func
Author(s): The Open University

I've never quite lost the sense of wonder at the way information can be transmitted with no visible link between the sender and recipient. When I was a child I used to think that sound came through the wire linking my family's radio to the mains electricity supply (I was born before the days of battery-powered transistor radios) and I couldn't understand why my parents referred to it as â€˜the wirelessâ€™ â€“ since clearly it wasn't. I now know that the wire simply fed the radio with the elec
Author(s): The Open University

The focus of Section 3 was on LANs that use some kind of physical medium (for example, copper wires or fibre-optic cables) to connect together network nodes. In this section we'll be examining wireless networks â€“ that is, networks that transmit data through the air (or space) using radio waves.

There's nothing new about wireless: the principles of transmitting information using radio waves were discovered over a century ago. However, using radio waves to provide the transmission links
Author(s): The Open University