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?

Answer


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3.10 A final word – analogue and digital worlds

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 of binary numbers.

Before I leave the topic, though, I should point out that some of the points I've made may be controversial.

For a start, it's not entirely clear whether the world we inhabit is fundamentally analogue. Quantum theory tells us, for instance, that quantiti
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3.3.2 Enhancing the perceptual system

Magnificently evolved though it is, our sensory system is nothing special. We do not see as well as birds; our hearing is feeble compared to that of bats and some forest-dwelling mammals. Our sense of smell can't compare with that of dogs or pigs. There are many things we don't detect at all – radio waves, for instance.

In one capacity, though, humans are supreme: we have learned to enhance our perceptual systems with instruments. For example, the human eye has only a limited p
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3.1 Ghosts of departed quantities

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
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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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Acknowledgements

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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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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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 signed integer 1010 10
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7.3.1 Finding the 2's complement

In Section 2.4 you saw how to find the 2's complement representation of any given positive or negative denary integer, but it is also useful to be able to find the additive inverse of a 2's complement integer without going into and out of denary. For instance, 1111 1100 (−4) is the additive inverse, or 2's complement, of 0000 0100 (+4), but how does one find the additive inverse without converting both binary integers to their denary equivalents?

The answer is that the additive inve
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6 Manipulating data in computers: introduction

Sections 1 to 5 of this unit have shown that in a computer all types of data are represented by binary codes, and that programmers must make sure that the programs they write treat this data appropriately in any particular application: as text if it is intended to be text, as a binary fraction if it is intended to be a binary fraction, and so on.

Programmers must also ensure that the programs manipulate the binary codes in an appropriate way for the particular application. But what sort
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4.2 Representing text

Study note: You will need to refer to the Reference Manual while you are working through this section.

Please click on the 'View document' link below to read the Reference Manual.

3.4 Input and output considerations

CCDs are not inherently able to detect colour, only brightness. So it is necessary to rely on the fact that any colour of light can be made up from the three primary colours of light: red, blue and green. (Note that the three primary colours of light are different from the three primary colours of pigments.) Each CCD in the array is therefore overlaid with a red, blue or green filter and so detects the brightness of, respectively, the red light, the blue light or the green light falling on it
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6.1 Networks

Next I'll be looking more closely at the ‘network’ block in Figure 8, and in particular at the links that must be present before communication can take place. I'll introduce you to just a few of the forms that these links can take; links may be physical ones, such as cables, or they
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3.1 Introduction

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
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4.9 Ethical, social and political aspects

The introduction of identity cards has proved controversial in several countries, for example France (where identity papers have long been a requirement) and Australia. Generally the issues have related to the questions like: ‘What are these cards actually for?’, ‘Whose interests do they serve?’ and ‘What use will be made of the underlying database of identity data?’ Opponents of identity schemes have pointed out that totalitarian regimes have always found identity systems very us
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6.1 Introduction

Section 5 discussed the ISMS planning and documentation process in general and also went into the details of Stages 1, 2 and 8 of the ISMS documentation task. In this section, we shall discuss Stage 3 of the ISMS documentation task and see how to define a systematic approach to risk assessment. We shall also look at the asset identification task. The remaining two tasks, risk assessment and risk treatment, are outside the scope of this unit.


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5.2 The Standard's approach to planning an ISMS

The Standard describes the planning of an ISMS, which it refers to as the ‘Plan activity’, as follows.

The Plan activity … is designed to ensure that the context and scope for the ISMS have been correctly established, that all information security risks are identified and assessed, and that a plan for the appropriate treatment of these risks is developed. It is important that all stages of the Plan activity a
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1 Why is information security important?

This unit introduces you to information security and its management.

A succinct definition of information security might run as follows:

Information security is the collection of technologies, standards, policies and management practices that are applied to information to keep it secure.

But why is it important to secure information? And how should its security be managed? To s
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11.3 Controlling cookies in Internet Explorer

It's important to remember that you have the ability to control cookies.

This exercise will take you through setting a level of security on cookies using Microsoft Internet Explorer version 6, while the next page deals with Mozilla Firefox version 1 (you do not have to be online to do this exercise).

Using Internet Explorer

  • Open your browser.

  • On the top menu bar of the browser choose Tools > Internet Options.

  • <
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4.1 What is a search engine?

Search sites are powered by a search engine: a program that can search for web pages that match your query, and then return a list of hits. The list of hits arrives at your browser as a web page, complete with links to the pages the search engine has found. A website such as the Open University may provide its own search engine which searches only its own web pages, but the big search sites claim to search the entire Web. This is a stunning claim: Google claims to search over four billion web
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