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References

Coffman, K. G. and Odlyzko, A. (1998) ‘The size and growth rate of the Internet’, First Monday, Vol. 3, Issue 10, http://firstmonday.org
ITU-T 1–150 (1999) B-ISDN Asynchronous Transfer Mode Functional Characteristics, ITU-T.
ITU-T X.200 (1994) Open Systems Interconnection – Model and Notation, ITU-T. (Also known as ISO/IEC 7498–1.)

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4.2.1 ATM physical layer

The ATM physical layer is divided into two sub-layers: the transmission convergence sub-layer and the physical medium sub-layer.

Functions of the transmission convergence sub-layer include generating and receiving cells, and generating and verifying the cyclic redundancy check in the header error control field. For correct interpretation of ATM cells it is important to identify the beginning of a cell. In theory, if ATM cells are transmitted as a continuous stream of bits,
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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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5.1 As to the meaning ...

And this song is considered a perfect gem,

And as to the meaning, it's what you please.

(C.S. Calverley, Ballad)

This short section is devoted to rounding off the discussion so far. In Section 1 I remarked that a digital picture of some set of interesting features of the world is of no value unless we can examine it in some way – in other words, take it back acros
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4.15 Summary

This has been a very long section; so congratulations on your persistence!

I've considered in detail how text, pictures, moving pictures, diagrams and sound can all be reduced to numbers and stored inside the boundary in a computer's memory. A persistent theme has been the sheer size of the digital representation that we can get as the result. The need to reduce this amount of digital data, to compress the image, sound or film file we end up with, is taken up in the next course.<
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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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4.4 Introducing pixels

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 will be exactly the same, whatever image we use.


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4.2.2 Standards

Representations must be agreed if they are to be shared. If different computers used different numbers to encode the same character, people would not be able to read each other's documents. There have to be standards. There are countless computer standards, covering every aspect of information technology, from music and picture encoding to programming language design. And, as you would expect, there are standards which apply to character encoding. You may have wondered why I cho
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2.3 The computer in the world

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, and grapple with, the world. This course explores:

  • the ways in which computers help us make contact with the world;

  • the many purposes we can achieve once a computer has been used to capture some part of the world.


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7.3.2 Subtraction

As I indicated at the start of this section, subtraction is converted to addition by replacing the number to be subtracted by its additive inverse, which in the case of binary arithmetic is its 2's complement. An example should make this clear.

Example 9

Subtract the signe
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References

Revell, P. (September, 2004) Miniature computers are adding up to fun [online] http://education.guardian.co.uk/elearning [story[0,10577,1314016,00.html Accessed 16 October 2006] Guardian Newspapers Ltd.

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17.3 The network

The network conveys the data on items purchased through to the database server. It also conveys data such as revised prices and special offers from the database server back to the checkout terminal. In both cases this may involve selecting an appropriate route through the network and manipulating, storing or retrieving data.


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13.2 Magnetic storage

As I mentioned earlier, your computer has a hard disk which provides a permanent storage area for your computer's programs and the files you create. When you save files to your computer's hard disk, you are using a magnetic storage medium. Data stored in magnetic form can be changed once it has been stored, so if you run out of space you can delete some files to make room or, if you want to edit a file, you can make the necessary changes and then save it again. At the time of writing, a mediu
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7 Describing an ICT system: conclusion

We have arrived at a model of a communication system that illustrates the processes needed for communication. We have also looked at the different kinds of communication link that can be used to convey data, and how to express the rates at which they can convey data. In sections 8–14, we shall be looking at a computer system as an example of an ICT system where data manipulation and storage are the most important features.

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Leadership and context
This free course, Leadership and context, introduces you to the potential impact of context and culture, both internal and external, on educational organisations and its implications for leadership. First published on Fri, 26 May 2017 as Leadership and context. To fi
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Talk the talk
This free course introduces the mechanics of effective, persuasive oral presentations, by giving you the opportunity to analyse examples and then create your own. Using resources such as TED Talk videos, you will see how experts deliver professional talks and famous speeches, observe what works, and identify how language connects ideas and keeps a listener engaged. First published o
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Introduction

This OpenLearn course is an adapted extract from the Open University course L120 Ouverture: intermediate French.

This OpenLearn course provides a sample of level 1 study in French.


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Listening to young children: supporting transition
In this free course, Listening to young children: supporting transition, you will explore ways of listening to children in order to support their experiences of changes or transitions. Such transitions can involve many dimensions, including familiarisation with new cultural practices, the development of new relationships and potentially a shift in identity, for example, from being a 'nursery child' to being a 'pupil'. During the course you will explore how listening to children as they go throug
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Being an OU student
In the course, you’ll get a flavour of what OU study is actually like, learn about how you’ll be supported, the technologies you’ll use and start to develop the skills you’ll need to succeed. First published on Wed, 08 Aug 2018 as Being an OU student. To fi
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