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Introduction to Computers and the Internet
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  1. 1 Introduction to Computers and the Internet

  2. OBJECTIVES In this chapter you will learn: • Basic computing concepts. • The different types of programming languages. • The evolution of the Internet and the World Wide Web. • What Web 2.0 is and why it’s having such an impact among Internet-based and traditional businesses. • What Rich Internet Applications (RIAs) are and the key software technologies used to build RIAs.

  3. 1.1 Introduction • Internet and World Wide Web How to Program: 4/e • Walkthrough of Web 2.0 • Emphasizes structured programming and object-based programming • Live-code approach • All concepts presented in full working program examples • Examples available at www.deitel.com/books/iw3htp4. • JavaScript, XHTML and CSS • Introduced in earlier chapters • Provides solid foundation for computer programming and rest of book

  4. 1.1 Introduction (Cont.) • Software • Instructions to command the computer to perform actions and make decisions) • JavaScript and PHP are popular software development languages for web-based applications. • Computer development • Computer use increasing in most fields • Computer costs and size decreasing • Abundance of silicon drives down prices of silicon-chip technology • Applications of this book • Prepares for higher learning in C++, Java, C#, Visual Basic.NET as well as object-oriented programming • Allows development of applications with graphical user interfaces (GUIs) • Multimedia capabilities • Integration with the Internet and World Wide Web

  5. 1.1 Introduction (Cont.) • Apply database technologies • Applications that are not limited to the desktop • Portability • Multiple platforms (i.e., different types of computers running different operating systems). • Book structure • Focus on Web 2.0 and rich Internet applications • Chapters 1-20 • Covers XHTML, JavaScript, Dynamic HTML, Extensible Markup Language (XML), CSS, Flash, Flex, Silverlight and Dreamweaver • For applications running on client side (typically Mozilla Firefox 2 and Microsoft Internet Explorer 7) • Chapters 21-28 • Cover web servers, databases, PHP, Ruby on Rails, ASP.NET, ASP.NET Ajax and JavaServer Faces (JSF)

  6. Fig. 1.1 | Architecture of Internet & World Wide Web How to Program, 4/e.

  7. 1.2 What is a Computer? • Computer • Device capable of • Performing computations • Making logical decisions • Works billions of times faster than human beings • Fastest supercomputers today • Perform hundreds of billions of additions per second

  8. 1.2 What is a Computer? (Cont.) • Programs • Sets of instructions that process data • Guide computer through orderly sets of actions specified by computer programmers • Computer system • Comprised of various hardware devices • Keyboard • Screen • Disks • Memory • DVD drives • Processing Units

  9. 1.3 Computer Organization • Every computer divided into six units 1. Input unit • “Receiving” section of computer • Obtains data from input devices Usually a keyboard, mouse, disk, scanner, uploads (photos and videos) and networks (Internet) • Places data at disposal of other units 2. Output unit • “Shipping” section of computer • Puts processed info on various output devices Screens, paper printouts, speakers • Makes info available outside the computer (e.g., Internet)

  10. 1.3 Computer Organization (Cont.) 3. Memory unit • Rapid access, low capacity “warehouse” • Retains information entered through input unit • Retains info that has already been processed until can be sent to output unit • Often called memory, primary memory, or random access memory (RAM) 4.Arithmetic and Logic Unit • “Manufacturing” section of computer • Performs calculations (addition, subtraction, multiplication and division) • Contains decision mechanisms and can make comparisons

  11. 1.3 Computer Organization (Cont.) 5. Central Processing Unit (CPU) • “Administrative” section of computer • Coordinates and supervises other sections • Multiple CPUs (multiprocessors) 6. Secondary storage unit • Long-term, high-capacity “warehouse” • Stores programs or data not currently being used by other units on secondary storage devices (like CDs and DVDs) • Takes longer to access than primary memory

  12. 1.4 Machine Languages, Assembly Languages and High-Level Languages • Three general types of programming languages • Machine languages • Assembly languages • High-level languages

  13. 1.4 Machine Languages, Assembly Languages and High-Level Languages (Cont.) • Machine languages • “Natural language” of a computer (aka object code) • Defined by hardware design of computer • Generally consists of strings of numbers • Are machine dependent • Cumbersome for humans • Example: Adding overtime pay to base pay and storing the result in gross pay +1300042774 +1400593419 +1200274027 • Slow and tedious for most programmers

  14. 1.4 Machine Languages, Assembly Languages and High-Level Languages (Cont.) • Assembly languages • Programmers began using English-like abbreviations to substitute for machine languages • Represents elementary operations of computer • Translator programs called assemblers convert assembly-language to machine-language • Example: LOAD BASEPAY ADD OVERPAY STORE GROSSPAY

  15. 1.4 Machine Languages, Assembly Languages and High-Level Languages (Cont.) • High-level languages • Developed as computer usage increased, assembly language proved inadequate and time-consuming • Single statements can be written to accomplish substantial tasks • Translator programs called compilers • Allow programmers to write instructions almost like every-day English • Example: grossPay = basePay + overTimePay

  16. 1.4 Machine Languages, Assembly Languages and High-Level Languages (Cont.) • High-level languages (II) • Much more desirable from programmer’s standpoint • Specific languages include • C, C++, Visual Basic.NET, C# and Java • Among most powerful and widely used languages today • Interpreter programs developed to execute high-level programs without compiling • Popular in program development environments • Once program developed, compiled version made • In this book, several key programming languages • JavaScript, ActionScript, PHP and Ruby on Rails—each of these scripting languages is processed by interpreters • Study markup languages • XHTML and XML, which can be processed by interpreted scripting languages • Achieve their goal of portability across a variety of platforms

  17. 1.5 History of the Internet and World Wide Web • ARPANET • Implemented in late 1960’s by ARPA (Advanced Research Projects Agency of DOD) • Networked computer systems of a dozen universities and institutions with 56KB communications lines • Grandparent of today’s Internet • Intended to allow computers to be shared • Became clear that key benefit was allowing fast communication between researchers – electronic-mail (email)

  18. 1.5 History of the Internet and World Wide Web • ARPA’s goals • Allow multiple users to send and receive info at same time • Network operated packet switching technique • Digital data sent in small packages called packets • Packets contained data, address info, error-control info and sequencing info • Greatly reduced transmission costs of dedicated communications lines • Network designed to be operated without centralized control • If portion of network fails, remaining portions still able to route packets

  19. 1.5 History of the Internet and World Wide Web • Transmission Control Protocol (TCP) • Name of protocols for communicating over ARPAnet • Ensured that messages were properly routed and that they arrived intact • Organizations implemented own networks • Used both for intra-organization and communication

  20. 1.5 History of the Internet and World Wide Web • Huge variety of networking hardware and software appeared • ARPA achieved inter-communication between all platforms with development of the IP • Internetworking Protocol • Current architecture of Internet • Combined set of protocols called TCP/IP • The Internet • Limited to universities and research institutions • Military became big user • Next, government decided to access Internet for commercial purposes

  21. 1.5 History of the Internet and World Wide Web • Internet traffic grew • Businesses spent heavily to improve Internet • Better service their clients • Fierce competition among communications carriers and hardware and software suppliers • Resulted in massive bandwidth increase and e costs • Tim Berners-Lee invents HyperText Markup Language (HTML) • Also writes communication protocols to form the backbone new information system = World Wide Web • Hypertext Transfer Protocol (HTTP)—a communications protocol used to send information over the web • Web use exploded with availability in 1993 of the Mosaic browser • Marc Andreessen founds Netscape • Company many credit with initiating the explosive Internet of late 1990s.

  22. 1.6 World Wide Web Consortium (W3C) • W3C Founded in 1994 by Tim Berners-Lee • Homepage at www.w3.org • Goals • Internet universally accessible • Standardization • W3C Recommendations: Technologies standardized by W3C include the Extensible HyperText Markup Language (XHTML), Cascading Style Sheets (CSS), HyperText Markup Language (HTML—now considered a “legacy” technology) and the Extensible Markup Language (XML). not an actual software product, but a document that specifies a technology’s role, syntax rules and so forth.

  23. 1.7 Web 2.0 • 2003 noticeable shift in how people and businesses were using the web and developing web-based applications • The term Web 2.0 was coined by Dale Dougherty of O’Reilly • Web 2.0 definition = companies use the web as a platform to create collaborative, community-based sites (e.g., social networking sites, blogs, wikis, etc.). • Web 1.0 (1990s and early 2000s) focused on a small number of companies and advertisers producing content for users to access • “brochure web”) • Web 2.0 involves the • Web 1.0 is as a lecture, • Web 2.0 is a conversation • Websites like MySpace , Facebook , Flickr , YouTube, eBay and Wikipedia , users create the content, companies provide the platforms.

  24. 1.7 Web 2.0 (Cont.) • Architecture of participation • Open source software • Collective • Rich Internet Applications (RIAs) • Software as a Service (SaaS) • Web services incorporate functionality from existing applications and websites into own web applications • Amazon Web Services • Maps web services with eBay web services

  25. 1.7 Web 2.0 (Cont.) • Future computers learn to understand the meaning of the data on the web = Semantic Web • Deitel Web 2.0 Resource Center at www.deitel.com/web2.0/ for more information.

  26. 1.8 Personal, Distributed and Client/Server Computing • 1977 Apple Computer popularized personal computing • Computers became economical for personal or business use • Machines could be linked together in computer networks • Local area networks (LANs) • Distributed computing • Workstations • Servers offer data storage and other capabilities that may be used by client computers distributed throughout the network, • Client/server computing • Popular operating systems • UNIX, Linux, Mac OS X and Microsoft’s Windows

  27. 1.9 Hardware Trends • Improving technologies • Internet community thrives on improvements of • Hardware, Software and Communications • Cost of products and services • Consistently dropping over the decades • Computer capacity and speed • Doubles every two years (on average) = Moore’s Law • Microprocessor chip • Laid groundwork in late 1970s and 1980s for productivity improvements of the 1990s • Hardware moving toward mobile, wireless technology. • Hand-held devices more powerful than early supercomputers • Portability • Wireless data-transfer speeds

  28. 1.10 The Key Software Trend: Object Technology • Objects • Reusable software components that model items in the real world (classes) • Makes software developers more productive • Object-oriented programs often easier to understand, correct and modify than older types of programs

  29. 1.10 The Key Software Trend: Object Technology (Cont.) • Object technology • Packaging scheme that helps create meaningful software units • Large and highly focused on particular applications areas • Before appeared, programming languages were focused on actions (verbs) rather than on objects (nouns) • Programmers would program primarily with verbs • Made program awkward • We live in a world filled with complex objects and simple actions

  30. 1.10 The Key Software Trend: Object Technology (Cont.) • Object technology (continued) • Object-oriented programming • Programmers work in manner similar to how they see the world • More natural process • Significant productivity enhancements • Procedural programming • Not particularly reusable • Forces programmers to constantly “re-invent the wheel” Wastes time and resources • Objects (classes) • Software modules • Kept in libraries • Reusable – save time and resources

  31. 1.11 JavaScript: Object-BasedScripting for the Web • JavaScript • Attractive package for advancing level of programming language education • Object-based language • Supports proper software engineering techniques • Free as part of today’s most popular Web browsers • Powerful scripting language • Portable • Programs execute interpretively on client machines • ActionScript and JavaScript are converging in the next version of the JavaScript standard (JavaScript 2/ECMA Script version 4) • Universal client scripting language, simplifying web application development

  32. 1.12 Browser Portability • Browser portability • Great challenge • Great diversity of client browsers in use • Many different platforms also in use • Difficult to • Know capabilities and features of all browsers and platforms in use • Find correct mix between absolute portability, complexity and usability of features

  33. 1.13 C, C++ and Java • C • developed by Dennis Ritchie at Bell Laboratories • development language of the UNIX operating system • virtually all new major operating systems are written in C and/or C++ • C++ • developed by Bjarne Stroustrup in early 1980s • “spruce up” the C language and provides capabilities for object-oriented programming • Java • developed by Sun Microsystems in 1991 • Sun saw the immediate potential of using Java to add dynamic content (e.g., interactivity, animations and the like) to web pages • Sun formally announced Java at an industry conference in May 1995 • Java is now used to • develop large-scale enterprise applications • enhance the functionality of web servers • provide applications for consumer devices

  34. 1.14 BASIC, Visual Basic, Visual C++, C# and .NET • BASIC • Developed in the mid-1960s at Dartmouth College • Primary purpose was to familiarize novices with programming techniques • Microsoft’s Visual Basic language • Based on Basic • Has become one of the most popular programming languages in the world • Microsoft’s .NET platform • Provides the capabilities developers need to create computer applications that can execute on computers distributed across the Internet • Visual Basic (based on the original BASIC) • Visual C++ (based on C++) • Visual C# (based on C++ and Java)

  35. 1.15 Software Technologies • Agile Software Development • Set of methodologies that try to get software implemented quickly • Agile Alliance (www.agilealliance.org) • Agile Manifesto (www.agilemanifesto.org) • Refactoring • Reworking code to make it clearer and easier to maintain while preserving its functionality • Design patterns • Proven architectures for constructing flexible and maintainable object-oriented software • Open source code

  36. 1.15 Software Technologies (Cont.) • Linux • Open source operating system • Apache • Most popular open source web server • MySQL • Open source database management system • PHP • Most popular open source server-side “scripting” language for developing Internet-based applications • LAMP • Linux, Apache, MySQL and PHP (or Perl or Python) • Game programming • Software techniques used in game programming Adobe Flash CS3 • Ruby on Rails • Combines the scripting language Ruby with the Rails web application framework • Developed by 37Signals • Software as a Service (SaaS) • Software runs on servers elsewhere on the Internet • Salesforce.com, Google, Microsoft and 37Signals all offer SaaS