IT in everyday life
We now live in a global village where distance is no longer a barrier to commercial or social contact. This free course, IT in everyday life, will enable you to gain an understanding of the information and communication technologies that drive our networked world and how they now permeate our everyday lives. First published on Thu, 19 Apr 2018 as Author(s): Creator not set

The digital scholar
Digital scholarship is a shorthand for the intersection of three technology related developments: digital content, networked distribution and open practices. It is when digital, networked and open intersect that transformational practice occurs. In this free course, The digital scholar, you will explore the impact of digital technologies on scholarly practice. First
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An introduction to web applications architecture
This free course, An introduction to web applications architecture, provides an overview of the design and implementation of computer software that runs on web servers, instead of those running solely on desktop computers, laptops or mobile devices. First published on Thu, 03 May 2018 as Author(s): Creator not set

Conclusion

  1. We discussed forms of data and processes relevant to an electronic till in a supermarket. In particular, we introduced the idea of a sequence of data items.

  2. A number of fundamental forms of data were introduced. We distinguished two types of number: integers (positive or negative whole numbers, or 0), and real numbers (thought of as decimal numbers and approximated in computers as floating point numbers). Characters may be thought of as symbol
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4.2 Functions defined through cases

In each of the examples considered so far, the function has had its semantics expressed using a formula or a general rule. Some functions have their semantics expressed simply by listing the output for each possible input. For example, let Days be the set of days of the week, and the function TOMORROW have signature DaysDays, and return the day following the input day. If we represent Days using the strings {“Mon”, “Tues”, “Wed”, “Thurs”
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2.3 Horizontal communication

In the OSI reference model there is a clear separation of services and protocols, but this separation is not always evident in practical applications, so it is worthwhile spending some more time on the differences between them. A service is provided by one layer to the layer above, and the capabilities of a service are defined in terms of primitives and their parameters. A service relates to two adjacent layers in the same system. In contrast, a protocol defines the communication between two
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1.1 Abbreviations used within this unit

While reading this subject you may come across the following abbreviations.

AAL – ATM adaptation layer

API – application program interface

ARP – address resolution protocol

ATM – asynchronous transfer mode

B-ISDN – broadband ISDN

CLP – cell loss priority

DNS – domain name system

FTP – file transfer protocol

HTTP – hypertext transfer protocol


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8 Conclusions

In this course you have learned about the difference between the analogue world we inhabit and the digital world of the computer.

I've described how features of our world can ‘cross the boundary’ and be represented or modelled in the digital world, and then brought back across the boundary to us.

More excitingly, computer programs that manipulate digital representations of our world enable us to:

  • simulate physical and social processes;<
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5.5.5 Summary

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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5.5.4 Loudspeakers

Speakers also produce an analogue output. The audio program inside the boundary converts the digital encoding of the sound to a series of electrical pulses that are sent to the speaker, where they cause a cone of stiffened paper (or some synthetic material) to vibrate in and out. This makes the air vibrate in the characteristic sound wave.


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5.5.3 Plotters

A plotter is a special type of printing device mostly used by architects, engineers and map makers. Here the printed output is produced by moving a pen across the paper. Sometimes several differently coloured pens are available. Plotters are obviously most suitable for line drawings, which is why architects, for instance, use them. I've mentioned them here, however, because – in contrast with monitors and printers – they produce an analogue output directly.


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4.11.1 Digital still cameras and camcorders

These devices are now widely and (fairly) cheaply available. There is no film. You point your camera, take your shot and get a compressed digital image that can be transferred straight onto a computer, where it can be edited or printed. Digital still cameras usually compress their images into JPEG format and store them on a tiny, removable memory card inside the camera; the latest digital camcorders can record in MPEG format, stored on a special tape. Both devices work by means of an electron
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4.2.3 Text capture devices

Practically, how can we take text across the boundary?

SAQ 8

What are the main devices for transforming text into digital form inside the computer?


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3.9 A few more terms

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. Specifically, you may have heard the terms bits, bytes and words used in connection with computers. Now that we have taken a look at the binary system that underlies computer arithmetic, you will find there is no mystery in any of these three terms.

The word Bit is
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3.3.1 The human perceptual system

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 systems that respond to many different features of their environment – insects, despite their impressive eyes, are most sensitive to trails of chemicals; bats are blind to light but responsive to sonar pulses; dogs and pigs depend more on smell than vision for sensing the world.

We w
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2.9 Summary

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.

I went on to look at the special nature of that tool, establishing that its function is to capture, store, present, exchange and manipulate interesting aspects of the world.

I then introduced the idea of two contrasting realms: the analogue world we inhabit and the digital interior world of the computer. When we capture featur
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2.7 Manipulation

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 go far beyond this. We can set up elaborate replicas of real-world systems and inspect them in detail. We can establish digital models and run them forward in time to see what might happen in the future. We can even create completely imaginary digital worlds and then explore them as if
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2.5: Crossing the boundary

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 world inside the computer are very different in kind. We live in an analogue world. The world of the computer is digital. The exact meaning of these terms may not be very clear to you at the moment. I will define them both in the next section. For the moment, the only point
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8.4 The OR operation

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
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