Introduction to Computers and the Internet
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Transcript of Introduction to Computers and the Internet
2008 Pearson Education, Inc. All rights reserved.
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Introduction to Computers and
the Internet
2008 Pearson Education, Inc. All rights reserved.
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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.
2008 Pearson Education, Inc. All rights reserved.
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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
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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
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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)
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Fig. 1.1 | Architecture of Internet & World Wide Web How to Program, 4/e.
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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
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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
1.2 What is a Computer? (Cont.)
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Every computer divided into six units1. 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)
1.3 Computer Organization
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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
1.3 Computer Organization (Cont.)
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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
1.3 Computer Organization (Cont.)
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1.4 Machine Languages, Assembly Languages and High-Level Languages
Three general types of programming languages– Machine languages
– Assembly languages
– High-level languages
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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
1.4 Machine Languages, Assembly Languages and High-Level Languages (Cont.)
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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
1.4 Machine Languages, Assembly Languages and High-Level Languages (Cont.)
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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
1.4 Machine Languages, Assembly Languages and High-Level Languages (Cont.)
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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
1.4 Machine Languages, Assembly Languages and High-Level Languages (Cont.)
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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)
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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
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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
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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
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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.
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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.
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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.
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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
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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.
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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
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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
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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
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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
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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
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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
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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
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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
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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)
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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
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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