Introduction to Computers and the Internet

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Internet & World Wide Web How to Program, 5/eCopyright © Pearson, Inc. 2013. All Rights Reserved.

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Copyright © Pearson, Inc. 2013. All Rights Reserved.

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Copyright © Pearson, Inc. 2013. All Rights Reserved.

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Copyright © Pearson, Inc. 2013. All Rights Reserved.

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The Internet and web programming technologies you’ll learn in this book are designed to be portable, allowing you to design web pages and applications that run across an enormous range of Internet-enabled devices. Client-side programming technologies are used to build web pages and applications that are run on the client (i.e., in the browser on the user’s device). Server-side programming—the applications that respond to requests from client-side web browsers, such as searching the Internet, checking your bank-account balance, ordering a book from Amazon, bidding on an eBay auction and ordering concert tickets. Copyright © Pearson, Inc. 2013. All Rights Reserved.

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Read the Preface and the Before You Begin section to learn about the book’s coverage and how to set up your computer to run the hundreds of code examples. The code is available at www.deitel.com/books/iw3htp5 and www.pearsonhighered.com/deitel. Use the source code to run every program and script as you study it. Try each example in multiple browsers. Copyright © Pearson, Inc. 2013. All Rights Reserved.

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If you’re interested in smartphones and tablet computers, run the examples in your browsers on iPhones, iPads, Android smartphones and tablets, and others. The technologies covered in this book and browser support for them are evolving rapidly. Not every feature of every page we build will render properly in every browser. Copyright © Pearson, Inc. 2013. All Rights Reserved.

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Moore’s Law Every year or two, the capacities of computers have approximately doubled inexpensively. This remarkable trend often is called Moore’s Law. Moore’s Law and related observations apply especially to the amount of memory that computers have for programs, the amount of secondary storage (such as disk storage) they have to hold programs and data over longer periods of time, and their processor speeds—the speeds at which computers execute their programs (i.e., do their work). Similar growth has occurred in the communications field, in which costs have plummeted as enormous demand for communications bandwidth (i.e., information-carrying capacity) has attracted intense competition. Copyright © Pearson, Inc. 2013. All Rights Reserved.

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Figures 1.1–1.4 provide a few examples of how computers and the Internet are being used in industry and research. Figure 1.1 lists two examples of how computers and the Internet are being used to improve health care. Copyright © Pearson, Inc. 2013. All Rights Reserved.

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Figure 1.2 provides a sample of some of the exciting ways in which computers and the Internet are being used for social good. Copyright © Pearson, Inc. 2013. All Rights Reserved.

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Figure 1.3 gives some examples of how computers and the Internet provide the infrastructure to communicate, navigate, collaborate and more. Copyright © Pearson, Inc. 2013. All Rights Reserved.

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Copyright © Pearson, Inc. 2013. All Rights Reserved.

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Copyright © Pearson, Inc. 2013. All Rights Reserved.

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Figure 1.4 lists a few of the exciting ways in which computers and the Internet are used in entertainment. Copyright © Pearson, Inc. 2013. All Rights Reserved.

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Copyright © Pearson, Inc. 2013. All Rights Reserved.

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Copyright © Pearson, Inc. 2013. All Rights Reserved.

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HTML5 HTML (HyperText Markup Language) is a special type of computer language called a markup language designed to specify the content and structure of web pages (also called documents) in a portable manner. HTML5, now under development, is the emerging version of HTML. HTML enables you to create content that will render appropriately across the extraordinary range of devices connected to the Internet—including smartphones, tablet computers, notebook computers, desktop computers, special-purpose devices such as large-screen displays at concert arenas and sports stadiums, and more.Copyright © Pearson, Inc. 2013. All Rights Reserved.

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A “stricter” version of HTML called XHTML (Extensible HyperText Markup Language), which is based on XML (eXtensible Markup Language), is still used frequently today. Many of the server-side technologies we cover later in the book produce web pages as XHTML documents, by default, but the trend is clearly to HTML5.Copyright © Pearson, Inc. 2013. All Rights Reserved.

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Cascading Style Sheets (CSS) Although HTML5 provides some capabilities for controlling a document’s presentation, it’s better not to mix presentation with content. Cascading Style Sheets (CSS) are used to specify the presentation, or styling, of elements on a web page (e.g., fonts, spacing, sizes, colors, positioning). CSS was designed to style portable web pages independently of their content and structure. By separating page styling from page content and structure, you can easily change the look and feel of the pages on an entire website, or a portion of a website, simply by swapping out one style sheet for another. CSS3 is the current version of CSS under development. Copyright © Pearson, Inc. 2013. All Rights Reserved.

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JavaScript JavaScript helps you build dynamic web pages (i.e., pages that can be modified “on the fly” in response to events, such as user input, time changes and more) and computer applications. It enables you to do the client-side programming of web applications. JavaScript was created by Netscape. Both Netscape and Microsoft have been instrumental in the standardization of JavaScript by ECMA International (formerly the European Computer Manufacturers Association) as ECMAScript. ECMAScript 5, the latest version of the standard, corresponds to the version of JavaScript we use in this book. JavaScript is a portable scripting language. Programs written in JavaScript can run in web browsers across a wide range of devices. Copyright © Pearson, Inc. 2013. All Rights Reserved.

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Web Browsers and Web-Browser Portability Ensuring a consistent look and feel on client-side browsers is one of the great challenges of developing web-based applications. Currently, a standard does not exist to which software vendors must adhere when creating web browsers. Although browsers share a common set of features, each browser might render pages differently. Copyright © Pearson, Inc. 2013. All Rights Reserved.

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Browsers are available in many versions and on many different platforms (Microsoft Windows, Apple Macintosh, Linux, UNIX, etc.). Vendors add features to each new version that sometimes result in cross-platform incompatibility issues. It’s difficult to develop web pages that render correctly on all versions of each browser. All of the code examples in the book were tested in the five most popular desktop browsers and the two most popular mobile browsers (Fig. 1.5). Copyright © Pearson, Inc. 2013. All Rights Reserved.

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Last Updated: 8th March 2018

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