4.1 Introduction

The 1970s marked a period in which the cessation of the ‘normal’ period of full-time employment at 60 or 65 years had become the accepted orthodoxy. The personal lives of older people had thus become constituted outside the domain of paid employment and within the arena of public and private welfare. As we illustrated in the preceding section, pensions, organised around fixed ages of retirement based on chronological measurements of age, played a crucial role in this process. Further, as
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3.3 Parenthood

The deeply embedded inequalities of marriage were also prevalent in parenthood, reflecting the key role of gender in structuring the inequalities found in both. Under common law fathers were given complete control over their children, while mothers had no rights of custody, care or access if the marriage broke down, or even if the husband died. A man could be adulterous or fail to provide for his family without depriving him of his rights. The Poor Laws provided the only legal requirement on
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4.3.2 Network externalities and increasing returns to scale

The reader should ask herself the following question: Would I subscribe to a telephone service knowing that nobody else subscribes to a telephone service?

The answer should be: Of course not! What use will anyone have from having a telephone when there is no one to talk to?

(Shy, 2001, p. 3)

The uncertainty surrounding production in the introductory phase, which places such importance on
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Learning outcomes

On completion of this unit, you should be able to:

  • identify criteria to evaluate the politics of racial violence.


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Learning outcomes

After studying this unit you should be able:

  • identify the value and best way of note taking.


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Design thinking
Are you ever frustrated with something that you thought you could design better? Design thinking can structure your natural creativity to come up with solutions to all kinds of problems, and have fun in the process too! First published on Thu, 22 Dec 2011 as Author(s): Creator not set

Key ideas

In this unit, we will take an introductory look at two key ideas: forms of data handled by a software system, and the processes that may be applied to that data. These ideas are illustrated by a particular application — a supermarket till — but they are of general relevance in designing software systems. Important terminology will be highlighted in bold.

In this unit we will look at some commonly occurring forms of data. We start with fundamental forms, such as
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4.11.2 Scanners (again)

In Subsection 4.2.5, scanners came up as devices that can convert text into digital form. They do this by making a digital image of the page and then passing this image to an OCR system to distinguish the various characters. However, they are more often used to take images such as photographs and printed
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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?

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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