2.4 Computer systems (contd) As I have already mentioned, the functional blocks shown in Figure 3 relate very closely to, even though they are not necessarily identical with, the computer's physical components. The computer's physical components are normally known collectively as the hardware. Software is a term often used to refer to a
Further reading References Keep on learning   There are more than 800 courses on OpenLearn for you to Conclusion This free course provided an introduction to studying Computing and ICT. It took you through a series of exercises designed to develop your approach to study and learning at a distance and helped to improve your confidence as an independent learner. 5.1 Introduction The final approach to developing distributed systems is based on a radical view of such systems. The approach is based on work carried out by two American academics, Nicolas Carriero and David Gelerntner. These two academics developed a language known as Linda in the 1980s. The language, and its associated technology, has always been thought of highly by other academics within the distributed systems area, but has never taken off in terms of commercial use. However, in the late 1990s Sun deve 4.1 Introduction Many of you will already be familiar with event processing if you have developed visual interfaces with the later versions of Java. Developing such an interface consists of a number of steps: A visual object such as a button is placed in a container such as an applet or a 2.3 Synchronous and asynchronous message passing Synchronous message passing involves one entity (usually a client) in the message passing process sending a message and a second entity (usually a server) receiving it, carrying out some processing and then sending back some response which the first entity processes in some way. While the second entity is carrying out the processing the first entity pauses waiting for the response. In asynchronous message passing each entity in the process does not have to wait for the next part Learning outcomes After studying this course, you should be able to: describe some of the architectural and programming paradigms used in distributed system development describe message passing and the role of protocols within a message passing paradigm introduce the concept of a distributed object describe how event-based architectures are used within distributed system development introduce one implementation of an event-based architec 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: Course image: Seika in Flickr made available under Creative Comm References 6.2.15 Free products and services It might seem paradoxical to include sites which provide free products or services under the category of business models. Typical sites which come under this category include gaming sites where users can play computer games using their browser, sites which run free raffles and sites which offer free software. Such sites do not earn any revenues from the products or services they offer; revenue is earned indirectly, for example by means of banner adverts or by receiving revenue from site 6 Correlation This activity demonstrates how a simple correlation analysis can be carried out. Correlations tell us about the relationship between pairs of variabl 2.5.5 Email providers These are sites which provide free email facilities; often they provide other facilities such as sending anonymous mail and constructing mailing lists. Such sites are valuable to users who are too impecunious to be able to afford conventional mailing software and to frequent travellers who can access such sites anywhere in the world. Their main disadvantage is that they tend to be slow compared with conventional mailing utilities such as Microsoft Outlook and Eudora. 2.5.2 Link checking sites The World Wide Web contains millions of web pages. Many of these pages are impossible to read, even though many existing web pages will reference them: your browser will usually return with some message such as ‘Error 404 Page not Found’ when you try to access them. Error 404 is a standard message returned by web servers when a non-existent page is accessed. It is also the telephone area code for Atlanta in the United States; you will occasionally hear technical staff referring to non-exi 2.5.1 Anonymous remailers An anonymous remailer is a website which enables you to send an email anonymously to some recipient. The main reason for this is to do with something known as spam. This term describes unsolicited email which tries to sell the recipient something. Throughout the 2.4 Auction sites These are sites on the web which run conventional auctions. There are two types of auction: those that are carried out in real time, where participants log in to an auction site using a browser at a specified time and bid for an article until the highest price is reached and no other bids are forthcoming. The other type of site – and the most common – is where an item is offered for sale and a date advertised after which no more bids are accepted. Such sites make a profit from two sources 2.1 An example – supply chain management Before looking at the wide variety of e-commerce application areas that have flourished over the last decade in more detail, it is worth looking at one which may not be familiar to a reader, but which saves companies huge amounts of resources. The application involves a supply chain. A supply chain is a set of relationships between a number of companies who have a symbiotic relationship with each other in that one company supplies commodities or services to other companies which, in tu Exploring children's difficulties with language and literacy Learning to change
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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
This free course, Learning to change, is for people who are thinking about making changes in their lives, such as returning to study or taking a different direction at work. It will help you build on what you already know; consider the choices open to you; use your skills and qualities to achieve change; and make plans for the future.
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