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
Author(s): The Open University

The leftmost bit at the start of a 2's complement integer (which represents the presence or absence of the weighting −128) is treated in just the same way as all the other bits in the integers. So the rules given at the start of Section 7.1 for adding unsigned integers can be used.

## Example 7

Author(s): The Open University

Sections 1 to 5 of this course 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 so
Author(s): The Open University

A moving image is simply a series of still images presented at sufficiently short time intervals that the eye smoothes over the change from one image to the next. In practice, this means the images must change at a minimum rate of around 20 per second; if the rate is lower then the moving image flickers or is jerky. Each still image that goes to make up a moving image is known as a frame.

So far as computers are concerned, moving images are of two types. One type is animations
Author(s): The Open University

4.1 Introduction

Personal computers, or PCs, are very versatile computers and can perform a huge range of tasks. So whereas the uses of the kitchen scales and the digital camera indicate clearly what types of data are to be represented, the PC leaves the field very broad indeed. I have therefore chosen to consider some of the data representations used when families and friends use emails to keep in touch. Very conveniently, these lead to some different data representations.

At their simplest, emails are
Author(s): The Open University

2.4 Representing numbers: negative integers

In Section 2.2 I showed you how integers can be encoded if they are known to be positive, treating the integers in the kitchen scales as if they were known to be positive. However, if the user invokes the ‘add-and-weigh’ function on the scales while there is an object in the scalepan and then removes t
Author(s): The Open University

16.4 The network

The term 'network' is used to describe some very different interconnected systems. In a home setting, you might have just two computers linked together to share documents and devices (such as a printer and a scanner) and to use the same internet connection. This setup is a network, albeit a small one. At the other end of the scale is a multinational company with a network of computers distributed all over the world.

A network belonging to a single organisation, where the computers are c
Author(s): The Open University

11.6 Operating systems

A computer requires software just to look after itself and to manage all its components; this is called the operating system. The operating system handles communication with the other software on the computer and with the hardware resources of the machine, such as the processor and memory. The operating system provides a means of running the computer's application programs. It also provides a standard user interface with windows, buttons and menus so that users can interact with the co
Author(s): The Open University

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.

Author(s): The Open University

2.2 A system map

One way of explaining and analysing a system is to represent it in a graphical form, known as a system map. I'll use the example of a system for making an appointment with a doctor in a health centre to illustrate this point. In this example, the health centre uses a computerised booking system and the patient may phone or visit the health centre to make an appointment. Therefore, the system includes a patient, a receptionist, a doctor, and a computerised booking system. The example sh
Author(s): The Open University

References

Eyewitness Travel Guide (1997) Amsterdam. London, Dorling Kindersley. pp. 120-1.
Götz, V. (1998) Color and Type for the Screen. Berlin, RotoVision (in collaboration with Grey Press).
Hartley, J. (1994) Designing Instructional Text. 3rd edn. London, Kogan Page.
Michaelis, P. R. and Wiggins, R. H. (1982) ‘A human
Author(s): The Open University

1.3.2 The characteristics of colour

Screens can only display a subset of the colours visible to the human eye. This limits the accuracy of colour reproduction. There is also variation between computers, so a web page on a PC may look different when viewed on a Macintosh. There are similar problems with colour printers.

These issues can cause problems for some sectors, such as the fashion industry.

There are also differences in the way we perceive colour from a screen compared to the way we perceive colour from paper
Author(s): The Open University

2.3 Searching for information on the Web

What do you do if you don't know the URL of the website you are looking for, or haven't been able to browse to it? The Web is not like a library – it isn't carefully organised and catalogued, and it is growing all the time. Luckily, there are search sites that can help you find what you want.

## 2.3.1 Portals

Author(s): The Open University

2.2 Browsing for information on the Web

One way to find what you are looking for on the Web is to start from sites that you know are likely to have useful 'links' on them, like the main Open University pages or the Open University Library pages. These opening pages are known as home pages and are a bit like the contents page of a book. The home page usually gives you some information about the content of the website, often with links to other pages of information held on that site and on sites elsewhere. By clicking on a link – w
Author(s): The Open University

Exploring children's difficulties with language and literacy
What happens if children aren’t making progress with language and literacy, and what sort of learning impairments might be the cause? How can the study of children’s thinking help us to understand these learning difficulties? This album offers insights into some of the problems faced by children with the developmental disorders dyslexia, poor comprehension and specific language impairment. In the main audio tracks, educators, therapists and researchers explore why children might have languag
Author(s): The OpenLearn team

Introduction

This course examines four of the ‘grand theories’ of child development: behaviourism, social learning, constructivism and social constructivism.

This OpenLearn course provides a sample of Level 2 study in Education.

Author(s): The Open University

5.1.2 Turning the negative into the positive

Here is a rewording of some of the negative student comments from Section 2, which we have re-worded into positive comments.

Negative Positive
I am no goo
Author(s): The Open University

## Table 2

Author(s): The Open University

Salim and Lewis mentioned that they found some sections of Layard's article difficult. So did I; for example, anyone without a background in economics would have difficulty grasping the arguments in paragraphs 13 and 14.

So what should you do when you can't make sense of what you read? Should you search online to find out about taxation theory? For my own satisfaction I searched for a definition of ‘marginal rate of taxation’ just to get the gist of it. I also tried to write down th
Author(s): The Open University

In order to make effective use of opportunities for developing your thinking, you need to develop a thinking disposition as well as thinking skills.

## Activity 6

The following checklist covers some of the important
Author(s): The Open University

Process word Meaning
Account for explain, clarify, give reasons for
Analyse resolve into its component parts examine critically or minutely
Assess