Introduction to Computers, the Internet and the World Wide Web

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Introduction to Computers, the Internet and the
World Wide Web

• Chapter 1

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1.1 Introduction

• Book is based on Suns Java 2 Platform, Standard
  Edition (J2SE).
• Sun provides a toolkit, called the J2SE
  Development Kit (JDK), that includes the minimum
  tools for writing software in Java.
• See java.sun.com/j2se.
• Book uses JDK version 5.0.
• Things change so fast, the books 6th edition
  came just 8 years after the 1st one.

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• Besides J2SE, there is also J2EE, The Java 2
  Platform, Enterprise Edition.
• It is for developing large-scale, distributed
  networking and web-based applications.
• J2ME, The Java 2 Platform, Micro Edition, is for
  developing applications for small,
  memory-constrained devices such as PDAs and cell
  phones.
• The authors also have an advanced book, Advanced
  Java 2 Platform How to Program.

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1.2 What Is a Computer?

• Modern computers can make perform computations
  and make decisions millions or even billions of
  times faster than humans.
• Todays supercomputers can perform hundreds of
  billions of additions per second.

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1.3 Computer Organization

• A computer has six logical pieces
• Input unit (keyboard, mouse, etc.)
• Output unit (monitor, printer, etc.)
• Memory unit
• ALU (performs math and logic operations)
• CPU (controls activity in system)
• Secondary storage unit (hard-drive, CD, DVD)

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1.4 Early Operating Systems

• Early systems ran one program at a time (batch
  processing).
• Multiprogramming allowed more than one program to
  run at a time.
• Time-sharing lets multiple users use the same
  computer at the same time.

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1.5 Personal, Distributed and Client/Server
Computing

• In the early days of computers, only businesses
  could afford them.
• Today they are inexpensive enough that people can
  own one or more.
• Networks have enabled communication between
  computers.
• A client system may communicate with a server
  system.

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1.6 The Internet and the World Wide Web

• In the beginning, the Internet connected about a
  dozen universities to share information.
• Now hundreds of millions of computers use the
  Internet world-wide.
• World Wide Web is the part of the Internet for
  finding and viewing documents.

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1.7 Machine Languages, Assembly Languages and
High-Level Languages

• Machine language is the natural language of the
  machine.
• It is in fact the only thing the machine can run
  directly.
• Assembly language uses mnemonics to represent
  machine instructions, thus making programming
  easier.
• High-level languages allow us to write code in a
  way very similar to our own language.

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1.8 History of C and C

• C language was developed from an earlier language
  by Dennis Ritchie at Bell labs in 1972. It found
  wide use in Unix systems.
• C is an extension of C by Bjarne Stroustrup in
  the early 1980s at Bell labs that added
  object-oriented capability to C.

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1.9 History of Java

• Sun recognized that microprocessors were finding
  there way into consumer-electronic devices, and
  thus funded a project that resulted in a
  C-based language.
• Its creater, James Gosling, first called it Oak,
  but finding that name already in use, Sun changed
  it to Java while meeting at a local coffee shop.

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• The consumer-electronics market needing such a
  language did not develop as fast as Sun expected
  and the project was in danger of being canceled.
• In 1993, the World Wide Web began to explode in
  growth, and Sun saw an opportunity to use Java to
  add dynamic content to web pages.
• Java was formally announced in May of 1995.

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1.10 Java Class Libraries

• In Java, programmers create classes to build a
  program.
• Java also provides a rich set of existing classes
  in the Java class library, also called the Java
  API.
• Thus, there are two areas of knowledge needed to
  program in Java the first is the language
  itself, the second is the set of classes in the
  class libraries.

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1.11 FORTRAN, COBOL Pascal and Ada

• Previous mainstream languages include
• FORTRAN for science and engineering
• COBOL for business applications
• Pascal for structured programming
• Ada for US DOD projects.

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• FORTRAN and COBOL are still widely used.
• Pascal found acceptance in academics but lacks
  features needed for commercial use.
• Ada is still used by the US DOD.

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1.12 BASIC, Visual Basic, Visual C, C and .NET

• BASIC (Beginners All-Purpose Symbolic
  Instruction Code) was for learning programming.
• Visual Basic is Microsofts language for easily
  creating Windows programs.
• .NET is Microsofts platform for developing
  Internet and Web applications.

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• Visual C is Microsofts tool for C
  development.
• Microsoft supports 3 languages for .NET
  development
• Visual Basic .NET
• Visual C .NET
• Visual C .NET
• .NET components written in different languages
  can be integrated together into a single
  application.

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1.13 Typical Java Development Environment

• There are 5 phases in Java Development
• Phase 1 Create the program
• Phase 2 Compile it
• Phase 3 Load it
• Phase 4 Verify
• Phase 5 Execute

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• There are many ways to create and edit a program
  (we will look at later).
• The compile step translates the source into
  byte-code, which is understandable to the Java
  virtual machine.
• The load step loads classes into memory.
• The verify step ensures the bytecode is valid and
  does not violate Javas security rules.
• In the execute step, the Java virtual machine
  (JVM) translates the bytecode to machine code for
  the particular machine it is run on.

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1.14 Notes about Java and Java How to Program,
Sixth Edition

• Java is a portable language, but portability is
  not always perfect.
• Always test programs on all systems in which you
  intend them to run.
• Suns Java documentation
• java.sun.com/j2se/5.0/docs/api/index.html
• java.sun.com/j2se/5.0/download.html
• java.sun.com/reference/docs/index.html
• You can view the source for Javas own classes.

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1.15 Test-Driving a Java Application

• Run the ATM application.

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1.16 Software Engineering Case Study
Introduction to Object Technology and the UML

• The ATM application serves as a case study in
  object-oriented software engineering.
• This will be an ongoing case study throughout the
  text.

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• Thinking in objects is easy because humans also
  think of the world as having objects.
• OOD (Object-oriented design) models the
  application domain using objects.
• OOAD (Object-oriented analysis and design) uses
  object-oriented thinking in both phases.

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• UML is the Unified Modeling Language for OO
  projects.
• Previously, there were different modeling
  approaches by different authors.
• The three main authors joined to create a single
  modeling language that combined the best of each.
• The authors are Grady Booch, James Rumbaugh, and
  Ivar Jacobson.
• Today the Object Management Group (OMG) oversees
  the UML standard.

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End of Slides