1.1 Getting an overview This section starts with an article from a technical journal – the sort that is read by academics and professionals working in a related technical field. It sets the scene for some of the technologies and issues that you will be encountering later in this unit. We're not going to ask you to read the entire article, but we would like you to get an idea of the article's contents, the kind of points the author is making, and the range of issues that it throws up. With this aim in mind, w
Acknowledgements The content acknowledged below is Proprietary (see terms and conditions). This content is made available under a Creative Commons Attribution-NonCommercial-ShareAlike 2.0 Licence
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2 2 Conclusion The versatile tiny transistor is now at the heart of the electronics industry. In the video clips you have seen the history of the incredible shrinking chip, its Scottish connections, and an explanation of the physics that make chips work as well as a reconstruction of making a transistor using the crude techniques of yesteryear.
7.4 Using flowcharts to describe a task (contd) Now consider what happens when you are weighing, for example, flour on a set of scales. You slowly add more flour to the scalepan until you reach the desired weight. As you do this the display constantly changes, showing the weight increasing as you add more flour. To do this, the scales’ computer must repeatedly examine the input and update the display each time it does so. The flowcharts in figures Author(s):
7.1 Introduction Earlier on I indicated that in order for a processor to perform a defined function it needs to be supplied with a list of instructions called a program. In this section I shall explore this idea a little further. Software can be split into two categories, application software and operating systems. Application software is the name given to programs which enable a computer to perform specific tasks. The program that processes the image in the digital camera is one example; a word
6 A look to the future So what will computers do for you next? Perhaps they will be the key to solving transport problems. Driverless cars, controlled by computers, are under development. If these ever come to fruition perhaps they could help to reduce the number of road traffic accidents by automatically reducing their speed when they come too close to another car. Or perhaps journeys could be made faster and less frustrating because cars will use communicating computers to analyse traffic density and move along t
5.2 Electronic kitchen scales A set of electronic kitchen scales is shown in Figure 7. Their basic operation is relatively simple. When they are switched on and, for example, a 500-gram object is placed in the scalepan, the display shows the digits 500 and the letter g. 2.2 Memory You should now be beginning to build up a picture of what a computer is: you know it needs input and output devices to communicate with the world outside and a processor to carry out the instructions that are programmed into it. But where are these instructions stored within the computer? The answer is that they are stored within what is called the computer's main memory, along with any data needed to carry them out. However, the main memory in computers like PCs is much too smal Acknowledgements The content acknowledged below is Proprietary (see terms and conditions) and is used under licence. Grateful acknowledgement is made to the following sources for permission to reproduce material within this unit. Figure 6 NanoElectronics Japan Figure 30 The Cottingley Fairies © Science and Society Picture Library 6.4 Pictures It used to be thought that a photograph could provide proof of an event – someone could be caught red-handed by a photograph, as proof of their guilt. ‘The camera never lies’, it was said. If you have a digital camera and have been ‘touching up’ photographs on your home computer you will know that this is far from true now. It is easy to lie with a digital photograph. The idea that the camera never lies has always been a myth, however. As far back as 1917 the photographs of th 6.2 Authority and the variety of information sources Technology has massively increased the number and variety of news sources that we have access to. We still have printed books, magazines and newspapers, while digital techniques have increased the number of broadcast radio and TV channels that we can get. On the Web we have access to online versions of many of these. This allows us access to media that previously would have been inaccessible. With traditional news sources such as these, we have some understanding of the authority that t 2.2 From waterfall to iterative development Historically, the first widely adopted software development process was the waterfall development process (or simply, waterfall). The waterfall process relies on the definition of sequential phases, as shown in Figure 1. Each phase starts only after the previous one has finished; all the analysis i 2.2 Fixed and adaptive protocols The protocol described above for a simple naming service is an example of a fixed protocol. This is a protocol whose vocabulary is fixed: it is embedded in the client and server's code and data and does not change. An adaptive protocol is one where the protocol changes. A fixed protocol could change over a period of time because the functionality provided by a server changes. However, this change will be over months or years rather than over seconds. There are some instances wher Acknowledgements The following material is Proprietary (not subject to Creative Commons) and used under licence (see terms and conditions). Grateful acknowledgement is made to the following for permission to reproduce material: Ince, D. Developing Internet Applications, chapters 1 and 4, published by Pearson Education Limited in collaboration with The Open University, © Pearson Education Limited, 2002, 2003. This publication forms part of an Open University course M360 Developing 6.2 The application The first application I shall describe is that of an online bookseller. Such a book sales system would carry out a number of functions: It would allow the user to browse through a catalogue of books. It would allow the user to browse through a list of the most popular books, with the list being updated every hour. It would provide the facility whereby a user can buy books and add them to a notional shopping basket. 4.1.3 No dynamic web pages Another example of a problem with web servers which arises from their original functionality is the fact that web pages were designed to be static: they were files which were stored on a computer and delivered in their stored form to anyone using a browser to access them. Many e-commerce and e-business applications require something much more dynamic, for example there are a number of financial service sites on the web which provide customers with up-to-date stock and share prices. These pric 4.1 Legacy technology The aim of Section 5 is to examine some of the issues and problems which affect the devekopment of Internet, e-commerce and e-business applications. The World Wide Web was developed as a way of dispensing documentation within the large research laboratory at CERN in Geneva. I am sure that the originator of the technology, Tim Berners-Lee, did not realise at that stage how it would expand and become a major component of our economic infrastructure. Because many of the developers o 1.8 Maintenance Databases are one of the more enduring software engineering artefacts; it is not uncommon to find database implementations whose use can be traced back for 15 years or more. Consequently, maintenance of the database is a key issue. Maintenance can take three main forms: Operational maintenance, where the performance of the database is monitored. If it falls below some acceptable standard, then reorganisation of the database, usuall 1.7 Testing The aim of testing is to uncover errors in the design and implementation of the database, its structure, constraints and associated user and management support. Testing is usually considered to involve two main tasks – validation and verification. Without adequate testing users will have little confidence in their data processing. Validation answers the question: has the right database been developed to meet the requirements? It attempts to confirm that the right database has been co 1.6.4 Supporting data management strategies Most of the development we've covered so far in this unit has focused on meeting specific user requirements – that is, ensuring the right data are constrained correctly and made available to the right user processes. However, other questions must also be addressed in order to support a data management strategy: How frequently should data be backed-up? What auditing mechanisms are required? Which users will be permitted to perform which functions? Which database tools and user processes wil
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