iw3htp4_01-FINAL



2008 Pearson Education, Inc. All rights reserved.

1

1

Introduction to
Computers and
the Internet

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2008 Pearson Education, Inc. All rights reserved.

2

The renaissance of interest in the web that we call Web 2.0
has reached the mainstream.

—
Tim O’Reilly

Billions of queries stream across the servers of these
Internet services
—
the aggregate thoughtstream of
humankind, online.

—
John Battelle, The Search

People are using the web to build things they have not built
or written or drawn or communicated anywhere else.

—
Tim Berners
-
Lee

Some people take what we contribute and extend it and
contribute it back [to Ruby on Rails]. That's really the basic
open source success story.

—
David Heinemeier Hansson, interviewed by Chris Karr at
www.Chicagoist.com

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2008 Pearson Education, Inc. All rights reserved.

3

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.

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4

1.1

Introduction


1.2




What Is a Computer?


1.3




Computer Organization


1.4




Machine Languages, Assembly Languages and High
-
Level
Languages


1.5




History of the Internet and World Wide Web


1.6




World Wide Web Consortium (W3C)


1.7




Web 2.0


1.8




Personal, Distributed and Client/Server Computing


1.9




Hardware Trends


1.10




Key Software Trend: Object Technology


1.11




JavaScript: Object
-
Based Scripting for the Web


1.12




Browser Portability


1.13




C, C++ and Java


1.14




BASIC, Visual Basic, Visual C++, C# and .NET


1.15




Software Technologies


1.16




Notes about
Internet & World Wide Web How to Program,
4/e


1.17




Web Resources

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5

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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9

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 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)


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
r
andom
a
ccess
m
emory (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.

C
entral
P
rocessing
U
nit (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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Performance Tip 1.1

Interpreters have an advantage over
compilers in scripting. An interpreted
program can begin executing as soon as it is
downloaded to the client’s machine, without
the need to be compiled before it can execute.
On the downside, scripts generally run much
slower than compiled code.

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Portability Tip 1.1

Interpreted languages are more portable than
compiled languages. Interpreters can be
implemented for each platform on which the
interpreted languages need to execute.

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Software Engineering Observation 1.1

Interpreted languages are more dynamic than
compiled languages. For example, server
-
side
applications can generate code in response to
user interactions, and that code can then be
interpreted in a browser.

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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 plummeting 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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Software Engineering Observation 1.2

Extensive class libraries of reusable software
components are available on the Internet.
Many of these libraries are free.

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Software Engineering Observation 1.3

Some organizations report that the key benefit
object
-
oriented programming gives them is not
software that is reusable but, rather, software
that is more understandable, better organized
and easier to maintain, modify and debug. This
can be significant, because perhaps as much as 80
percent of software cost is associated not with the
original efforts to develop the software, but with
the continued evolution and maintenance of that
software throughout its lifetime.

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1.11 JavaScript: Object
-
Based

Scripting 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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Good Programming Practice 1.1

Write your programs in a simple and
straightforward manner. This is sometimes
referred to as KIS (“keep it simple”). One key
aspect of keeping it simple is another
interpretation of KIS
—
“keep it small.” Do not
“stretch” the language by trying bizarre us
es.

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2008 Pearson Education, Inc. All rights reserved.

40

Portability Tip 1.2

Although it is easier to write portable
programs in JavaScript than in many other
programming languages, differences among
interpreters and browsers make portability
difficult to achieve. Simply writing programs
in JavaScript does not guarantee portability.
Programmers occasionally need to research
platform variations and write their code
accordingly.

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41

Portability Tip 1.3

When writing JavaScript programs, you need
to deal directly with cross
-
browser portability
issues. Such issues are hidden by JavaScript
libraries (e.g., Dojo, Prototype, Script.aculo.us
and ASP.NET Ajax) which provide powerful,
ready
-
to
-
use capabilities that simplify
JavaScript coding by making it cross
-
browser
compatible.

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42

Error
-
Prevention Tip 1.1

Always test your JavaScript programs on all
systems and in all web browsers for which
they are intended.

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43

Good Programming Practice 1.2

Read the documentation for the JavaScript
version you are using to access JavaScript’s
rich collection of features.

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2008 Pearson Education, Inc. All rights reserved.

44

Error
-
Prevention Tip 1.2

Your computer and JavaScript interpreter
are good teachers. If you are not sure how a
feature works, even after studying the
documentation, experiment and see what
happens. Study each error or warning
message and adjust the code accordingly.

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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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Portability Tip 1.4

The web is populated with many different
browsers, which makes it difficult for authors
and web application developers to create
universal solutions. The W3C is working
toward the goal of a universal client
-
side
platform.

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47

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


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