3.2 Domain name system Applications use easy-to-remember names for hosts on the Internet, but before sending any data to a host an application in the source host must translate its name for the destination host to the numerical network address. The Internet is divided into domains, and an authority in each domain is responsible for allocating names. However, the domains may be divided into sub-domains and the responsibility of allocating sub-domain names may be delegated to other authorities. In this way the
3.1 What does TCP/IP protocol architecture do? The Internet is a worldwide public internetwork, which allows computers to communicate with each other even though they may have different manufacturers and different operating systems. The origins of the Internet lie in a project of the US Defense Advanced Research Project Agency in the 1970s, where it was intended to foster communication between research institutions rather than operate for profit. However, a substantial amount of traffic carried by the Internet is now related to com
2.1 Layers of communication An internetwork is a network of networks, composed of terminals, switches and communication media. The overall objective of an internetwork is to allow communication between two (or more) networks. This simple description hides the complications that arise in real networks, in which the types of medium vary, transmission errors occur, transmission links fail, switches fail or become congested, equipment is produced by different manufacturers, networks are owned and maintained by differ
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, which e
2.4.4 Manipulation Suppose I take a digital photograph of myself for my website. Horrified by my wrinkled, baggy appearance, what can I do? Actually, with the right software I can do more or less anything I like: I can smooth out the wrinkles; I can restore the grey hair to its former splendour; I can even put in a background of books to give me a scholarly appearance. In fact, I can so improve the picture that if you met the real me you probably wouldn't recognise me. ‘Massaging’ my photographic imag
8.3 The AND operation The AND operation combines two binary words bit by bit according to the rules 0 AND 0 = 0 0 AND 1 = 0 1 AND 0 = 0 1 AND 1 = 1 In other words, only when both bits are 1 is the result 1. You may find it helpful to think of it this way: when one bit is one and the other bit is 1 the result is 1. Acknowledgements Except for third party materials and otherwise stated (see terms and conditions). This content is made available under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 Licence 17.2 The checkout terminal The first computer block represents the checkout terminal. The processes at the checkout (receiving, storing, retrieving, manipulating and sending data to the user), are the same as I described earlier. However, the checkout terminal also sends data via the supermarket's network. 16.2.2 Storing and retrieving data As each item is scanned, the checkout computer looks up its price. The running total for each customer's purchases is stored temporarily in the checkout terminal. Other data may also be stored, such as the amount of money that has been taken at that checkout during the day. 13.2 Magnetic storage As I mentioned earlier, your computer has a hard disk which provides a permanent storage area for your computer's programs and the files you create. When you save files to your computer's hard disk, you are using a magnetic storage medium. Data stored in magnetic form can be changed once it has been stored, so if you run out of space you can delete some files to make room or, if you want to edit a file, you can make the necessary changes and then save it again. At the time of writing, a mediu 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 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 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 2.1 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 Introduction In this course you will be building on your previous study and experience of ‘working with others’. Using the notion of ‘teamwork’, you will be asked to think specifically about the values and beliefs underpinning the following three aspects of practice: developing working relationships with other professionals; sharing information and skills with other professionals; working in cooperation with other professionals 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. Introduction This course explores the role of digital media as a teaching tool, focussing on video in particular. We will examine the process of how you can start to use digital video in the classroom, and how to manage your project from objective setting, through story boards and filming, to assessing the success of the final result. This OpenLearn course provides a sample of postgraduate study in Author(s): Understanding society: Families Continuity and learning The family at the centre of early learning
In this free course, Understanding society: Families, you will explore how different families have different ideas about how work in the home should be divided. You will also investigate the diversity of families. We will see how any discussion of the division of labour has to recognise that families differ in terms of shape and size.
This free course, Continuity and learning, has a practical and professional development focus. You will explore interactive dimensions of workplace learning: how people and workplace cultures create formal, informal, planned and unplanned opportunities to learn. You will read about 'biographical learning' research, where adults develop narratives to better understand key points of their learning lives. You will plan and carry out a brief, informal interview with a colleague, and your colleague w
This free course, The family at the centre of early learning, focuses on the positive learning relationships that can exist in any family and how ordinary, everyday domestic activities can sustain learning. You will consider how the traditions and cultural practices of the community to which the family belongs filters through to the child’s experiences. In doing so you will think about why such influences may not have a uniform impact from family to family. You will also explore how learning i
