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Topic outline

 

  • Time: 20 hours
    Level: Introductory

 
 

Introduction

  • Introduction Resource
  • 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...
 

1 Aims

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

2 The worlds we live in

  • 2.1 Between two worlds Resource
  • Between two worlds life hovers like a star,
  • 2.2 Sensual world Resource
  • Just back home after a night walk, Klingsor stood on the narrow stone balcony of his studio. Below him, dizzyingly precipitate, the old terrace gardens dropped away, a densely shadowed tangle of tree tops,...
  • 2.3 The computer in the world Resource
  • I want to stress what, for me, is the main point. Computers exist because of our human need to reach out into the world. The computer is a tool which, like all tools, strengthens our ability to reach into,...
  • 2.4 The pervasive computer Resource
  • We can start with a simple proposition:
  • 2.3: Crossing the boundary Resource
  • So computers are used to acquire, store and present, exchange, and manipulate interesting characteristics of the world. But this raises a serious problem: the world we inhabit and know so well and the...
  • 2.5 Going back Resource
  • 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....
  • 2.7 Manipulation Resource
  • As I suggested above, we can change a digital version of some aspect of reality in any way we want. I've used the simple example of tinkering with a digital photograph, but the possibilities for transformation...
  • 2.8 The price Resource
  • But using computers to acquire, store, exchange and manipulate data comes at a price. By this, I don't mean that the technology is expensive, although this may be an issue. Rather it's the fact that the...
  • 2.9 Summary Resource
  • In this section, I started by emphasising the fact that the computer, which has become more or less omnipresent in modern society, is a tool like any other.
 

3 Analogue information: digital representation

  • 3.1 Ghosts of departed quantities Resource
  • They are neither finite quantities, or quantities infinitely small, nor yet nothing. May we not call them the ghosts of departed quantities?
  • 3.2 Analogue things Resource
  • In Section 2, I claimed that we lived in an analogue world, but put off defining what the term ‘analogue’ means. Here is a starting point: analogue quantities are ones that change continuously.
  • 3.3 How we perceive things Resource
  • In order to survive, all living things have evolved some sort of ability to sense or perceive the world around them. Even the humble amoeba is sensitive to light. Complex animals have intricate perceptual...
  • 3.4 Discrete things Resource
  • In contrast to analogue quantities, which change continuously, discrete quantities change in a series of clear steps.
  • 3.5 Digital things Resource
  • The terms ‘discrete’ and ‘digital’ are often used interchangeably. For example, The New Penguin Dictionary of Computing contains the following definition.
  • 3.6 A world of numbers Resource
  • Although we may not all enjoy it, using numbers to count and do arithmetic seems to be a natural human activity. For computers, however, there is nothing but numbers. They were designed from the first...
  • 3.7 How we work with numbers Resource
  • Most civilisations have had to face the problem of counting and recording numbers. Our own culture has adopted the so-called Arabic system of numbers. This system is now used more or less worldwide. In...
  • 3.8 How computers work with numbers Resource
  • Today's mass media wrap computers in a damaging myth. The message of TV thrillers seems to be that computers are inscrutable, subtle devices, far beyond the ordinary person's comprehension. Only spectacularly...
  • 3.9 A few more terms Resource
  • Just to round off this description of the interior of the digital world, let me introduce and define a few more terms that you will come across again in this course and in any future studies of computers....
  • 3.10 A final word – analogue and digital worlds Resource
  • So there we have it. On the one hand is our world, an analogue world – a world of light and sound, of taste and touch. On the other side of the boundary is the computer's digital world – a bleak world...
  • 3.11 Summary Resource
  • In this section I examined the terms analogue, discrete and digital and illustrated their correct use through examples and brief definitions.
 

4 Crossing the boundary

  • 4.1 Mere numbers? Resource
  • If I could write the beauty of your eyes
  • 4.2 Text Resource
  • As I said in Section 2, the human perceptual system is very strongly based on vision and hearing. When we think, we usually do so in terms of pictures and, perhaps to a lesser extent, spoken words and...
  • 4.3 Graphics and video: images Resource
  • Vision is far and away humankind's most dominant sense. Every sighted person lives their entire waking (and dreaming) life at the centre of a visual field, a sphere of light, shade, colour, form and movement....
  • 4.4 Introducing pixels Resource
  • Let's try a simple example. I'm going to take an image, divide it into discrete parts and then transform the result into numbers. I shall use the simple picture of a church shown in Figure 12(a). The process...
  • 4.5 Resolution Resource
  • What do you think could be done to improve the quality of the image?
  • 4.6 Greyscale Resource
  • If this seems inadequate – it does seem rather an impoverished range of shades – all we need to do is allocate more bits. Three bits per pixel will give us eight shades, from black to white; four bits...
  • 4.7 Colour Resource
  • Now what about the issue of colour? You should know enough to answer the question without prompting. So far, we've allocated a suitable number of bits to each pixel to give us the range of shade we need....
  • 4.8 Interlude – diagrams Resource
  • Some types of visual information can be represented more economically than in a bitmap. Consider the rather pointless little diagram shown in Figure 21.
  • 4.9 Making it move Resource
  • To me, there is a wonderful quality of timelessness about Vermeer's picture of the young woman at her harpsichord. It captures a tranquil moment, frozen for eternity. But of course our visual world is...
  • 4.10 Standards again Resource
  • Whatever compression strategy we adopt – and most real-life approaches use a combination – we again need to have agreement. If I compress a photograph using a certain technique and send it to a friend,...
  • 4.11 Image and video capture devices Resource
  • Earlier, we looked at keyboards and scanners as a means of taking text across the boundary.
  • 4.12 Sound and music Resource
  • Second only to vision, we rely on sound. Music delights us, noises warn us of impending danger, and communication through speech is at the centre of our human lives. We have countless reasons for wanting...
  • 4.13 Sound capture devices Resource
  • In the past, the work of recording sound and music was carried out by professional recording studios. Before digital technology arrived, recordings were made by picking up sounds on a microphone which...
  • 4.14 A final word Resource
  • I've looked at specific techniques for taking features of our analogue world across the boundary into the digital realm. All these methods have worked along the same lines – a two-step process consisting...
  • 4.15 Summary Resource
  • This has been a very long section; so congratulations on your persistence!
 

5 Going back

 

6 What if? … changing the digital world

  • 6.1 Kings of infinite space? Resource
  • I could be bounded in a nutshell and count myself a king of infinite space, were it not that I have bad dreams.
  • 6.2 Mimicking and mastering nature: manipulating the digital world Resource
  • Encoding images and sound is all very well, and has had billion-dollar effects on the publishing, recording and film industries. But can we be more ambitious? How about capturing features of the wider...
  • 6.3 Models Resource
  • So how could one go about creating a model of our planet's climate, or (even more daunting) the universe itself? What exactly is a model anyway?
  • 6.4 Setting models in motion – the power of simulation Resource
  • Our universe – everything about us – appears to obey laws, which govern how aspects of the world relate to one another. Scientists refer to these as natural laws, as they seem to be constants of nature,...
  • 6.5 Imaginary worlds Resource
  • Are you bored with your surroundings? Do you sometimes wish you were someone else? Help may be at hand. All the digital models we have looked at so far are based on our own world. But we needn't be limited...
  • 6.6 Worlds without end Resource
  • I wish this section could have been longer and that I could have written about:
  • 6.7 Summary Resource
  • This section has looked at simulations, in which digital models of key aspects of the real world can be manipulated by programs. The examples included models of the world's climate, the early cosmos, stock...
 

7 Crossing the boundary – a final word

 

8 Summary

  • 8 Summary Resource
  • In this unit you have learned about the difference between the analogue world we inhabit and the digital world of the computer.
 

Key terms

 

References and Acknowledgements

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